A review of transition metal dichalcogenides for supercapacitor applications: materials, performance, and challenges

Abstract

Supercapacitors (SCs) are environmentally friendly and sustainable innovations in energy transformation and storage. SCs provide a promising solution to fossil fuel depletion on account of their impressive power density (P_d) together with durable cycling lifespan, which makes them vital for modern electronic and electrical applications. However, they still face challenges, such as enhancing energy density (E_d) values, which remain a critical issue for the SC community that needs to be comprehensively tackled to meet the growing need for clean energy technologies. Significant attention has been garnered by two-dimensional (2D) transition metal dichalcogenides (TMDs) owing to their promise as key electrode materials in SCs. The excellent surface tunability, large electrochemically active exposed surface, and elevated electrical charge transport ability featuring adjustable oxidation levels facilitate efficient energy storage through pseudo-capacitive and electrical double-layer charge storage mechanisms. This review covers SC fundamentals, key components influencing E_d, and electrochemical evaluation techniques like galvanostatic charge–discharge (GCD), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV). It also provides a detailed analysis of the structural properties and synthesis routes of TMD-based electrodes, highlighting how doping, defect modulation, and composite engineering synergistically improve the electrochemical performance of TMD-based SCs. However, to fully unlock and optimise their capabilities, future research should be focused on integrating in situ characterisation, surface functionalization, and morphological engineering to enhance understanding of material behaviour. Additionally, integrating Density Functional Theory (DFT) simulations with machine learning-assisted calculations can accelerate the discovery and optimisation of high-performance materials for next-generation energy storage applications.

---

1. Introduction

Energy is a critical area of focus because energy resources are vital for both residential and industrial applications. Currently, fossil fuels are the dominant energy source and a major contributor to global warming. The progressive reduction in fossil fuel usage, as well as the ecological impact of greenhouse gas releases, has driven the worldwide development of sustainable energy supplies.^1,2 The risks tied to the exploitation of fossil fuels might be addressed by utilising alternative renewable energy sources, including tidal, thermal, wind, hydro, and solar energy, which are environmentally friendly, and their associated technologies have been globally competitive.^3,4 However, renewable energy conversion technologies are confronted with a critical challenge due to intermittent energy production, leading to interruptions in energy supply. As a result, the electrical energy produced by these sources is intermittent and does not reliably provide a continuous supply for domestic and commercial utilisation. Consequently, electrical energy storage systems have gained significant attention from researchers as a solution to overcome the barriers of continuous energy production and distribution, ensuring a stable and on-demand energy supply.^3,4

Batteries⁵ and supercapacitors (SCs)⁶ are vital energy storage devices (ESDs) recognised for their superior energy density (E_d), power density (P_d), mobility, and optimal life cycles.⁷ Among batteries, rechargeable systems have become the backbone of modern energy infrastructure, owing to their ability to store and deliver energy efficiently, making them key enablers of the renewable energy revolution.⁸ However, the growing demand for rapid energy delivery and high-power performance has drawn increasing attention to SCs. In this context, SCs have become essential due to their exceptional P_d and seamless integration with diverse energy conversion systems.^9,10 Whether it's enabling electric vehicles to charge within minutes or accelerate beyond 60 mph in seconds, SCs are increasingly being adopted for specialised applications worldwide.⁹ SCs offer a significant advantage over other contemporary energy retention technologies by virtue of their exceptional storage properties as well as excellent P_d. Due to these distinct characteristics, including high P_d, longer life cycles, high specific capacitance (C_s), superior low-temperature performance, and non-hazardous waste management, they can be considered environmentally sustainable. Along with this, SCs can be charged rapidly with quick power delivery, making them a viable intermediary between a battery and conventional capacitor, as can be seen in Fig. 1(a).^11–13 Although SCs store less charge than batteries, they can provide a thousand times more power than batteries.^14,15 Furthermore, unlike batteries, SCs are safer, posing no explosion risk even when overcharged.^11,12

Fig. 1 (a) Comparison of E_d and P_d in different energy storage technologies, represented through a Ragone plot; (b) number of publications on TMDs and SCs by year, based on Web of Science searches in April 2026, using keywords “transition metal dichalcogenides” or “TMDs” and “supercapacitors” or “SCs”.

Generally, SCs can be categorised into three distinct types based on their charge storage mechanisms: electric double layer capacitance, which occurs through charge segregation at the electrolyte/electrode junction; and faradaic pseudo-capacitance, which results from rapid, reversible absorption/desorption or reduction–oxidation reactions on or around the electrode face, besides asymmetric SCs.^15,16 Among these, asymmetric SCs can be generally categorised into two categories: configurations with two capacitive electrodes or hybrid capacitors. Furthermore, hybrid capacitors are recognised as a system where charge accumulation occurs at a single electrode through battery-style faradaic reactions, while the counterpart electrode utilises a capacitive-type storage method.^4,17 SCs are predominantly found in current fields, including electronic gadgets, voltage regulation devices, minimal-power device buffers, motorised tools, and hybrid automobiles, alongside industrial and medical use instruments. They may be used independently or in conjunction with batteries to enhance the lifespan of the latter and achieve a balanced power and E_d as needed. A well-designed SC system can provide this balance, making it ideal for current applications where improving the operational life of batteries and optimising the energy-power balance is crucial.^15,18 Electrode materials as well as electrolytes have a vital involvement in advancing SC capability and enabling their commercialisation.^11,19,20 These components directly impact key characteristics such as C_s, operating voltage, E_d, and P_d values.

Addressing the increasing worldwide need for efficient, high-performance, and eco-friendly energy storage has led to extensive research into advanced electrode materials for supercapacitors. These are crucial for use in portable electronics, electric vehicles, and large-scale energy storage systems.²¹ Traditional SC electrodes based on activated carbon typically use binders, which serve as inert components that reduce the functional area of the electroactive material and add unwanted weight, resulting in bulkier devices.^22,23 The discovery of graphene, a remarkable material, has paved the way for significant advancements in energy retention enabled by its vast surface area, superior electrical conductivity, and robust physical stability.^24–28 Despite extensive studies, graphene-based SCs still exhibit lower E_d than lithium-ion batteries.^29,30 Owing to the fact that graphene primarily stores charge via the EDL (i.e. electrochemical double layer) on the electrolyte/electrode junction, its capacitance is primarily governed by surface area and ion accessibility, rather than by faradaic reactions. In order to enhance efficiency, redox materials, including transition metal oxides (for example, MnO₂ and RuO₂) and polymers that show electrical conductivity (for example, polyaniline (PANI) and polypyrrole (PPy)), are incorporated; however, this compromises the cycle life.^31–34 Transition metal-derived materials, excluding graphene-based composites, have been largely explored as materials for electrodes due to their excellent capacitance, high-rate capability, and cost-effectiveness.^35,36 Nevertheless, challenges such as constrained surface area, short cycling lifespan, and inadequate electrical conductivity hinder their efficiency. Therefore, several approaches can be employed to overcome these limitations, including (1) morphology control, (2) composite formation of electrode materials to achieve synergistic effects, (3) doping elements into electrode materials to boost redox activity, and (4) manipulation of defects.^9,11,37,38

Recently, advances in materials science have highlighted metal-based two-dimensional (2D) layered materials, such as transition metal dichalcogenides (TMDs), beyond conventional graphene, as highly promising electrode candidates for advanced supercapacitors (Fig. 1(b)). Nonetheless, recent advances in materials science indicate that 2D layered materials have secured noteworthy popularity as electrode materials in advanced capacitors, owing to their extensive surface area resulting from the full accessibility of surface atoms.^39,40 The edge sites in thin 2D nanosheets are more chemically active than the basal plane, and the exposed van der Waals voids facilitate ion intercalation from the electrolyte, further enhancing their performance. Additionally, their high mechanical strength and atomic-scale dimension flexibility make them suitable for next-generation wearable electronics.⁴¹ Apart from graphene, there exist numerous types of 2D materials, such as layered transition metal dichalcogenides (TMDs), that have become highly promising candidates for SC electrodes.^26–28 TMDs consist of layered inorganic materials containing transition metals (M) and chalcogens (X: S, Se, and Te) arranged in an X–M–X structure with the chemical formula MX₂. They possess a wide array of physicochemical properties, making them very attractive for both fundamental studies and practical applications.⁹ Nowadays, various 2D TMDs are employed for SC electrodes, including molybdenum disulfide (MoS₂), molybdenum diselenide (MoSe₂), tantalum disulfide (TaS₂), tantalum diselenide (TaSe₂), niobium disulfide (NbS₂), tungsten disulfide (WS₂), tungsten ditelluride (WTe₂), tungsten diselenide (WSe₂), titanium disulfide (TiS₂), vanadium disulfide (VS₂), vanadium diselenide (VSe₂), zirconium disulfide (ZrS₂), etc.⁹ Furthermore, MoS₂, MoSe₂, WS₂, and WSe₂ have emerged as the most studied TMDs for their crucial role in augmenting electrochemical efficiency within energy retention and conversion technologies.⁴² Major TMDs exhibit a layered structure featuring weak interlayer bonding through van-der Waal force (for example, group 4–7 TMDs), while some are non-layered (for example, group 9–10 TMDs).^43,44 They can exist in either the 1T/2H structure (for example, group 5 TMDs) and typically favour 1T (for example, groups 4 and 7) or 2H (for example, group 6), each with distinct physical properties, i.e. the 2H phase, characterised as semiconducting with an inadequate electrical conductivity, and the 1T phase, which is normally metallic and highly conductive.^44–48 The extraordinary electrical, optical, and catalytic properties of 2H-TMDs have positioned them as a leading choice for a wide range of energy-related applications. Conversely, T-phases usually display metallic properties, greatly improving charge transfer efficiency in different energy-related applications. Nonetheless, 1T meta-stable materials, such as MoS_2, can undergo a spontaneous transition to the H-phase. Controlling the preparation of the metallic phase continues to be a major challenge. TMDs can be used as electrodes in SCs in their bulk state, but their properties change significantly when reduced to single- or few-layer thicknesses. A significant limitation of bulk TMDs is their low surface area.^42,43,49 However, the nano-optimisation of TMDs into zero-, one-, and three-dimensional structures offers a compelling technique to overcome their natural shortcomings. Moreover, the transition of phases in TMDs, from 2H semiconducting to 1T metallic, has ignited significant interest in developing a novel category of metallic TMDs exhibiting significant potential to achieve enhanced E_d (Fig. 2).⁹

Fig. 2 Classification of TMDs based on their dimensionality, electronic properties, and structures.

Numerous reviews delved into different aspects of TMDs, along with their fabrication methods, intrinsic characteristics, and SC applications.^50–55 Thomas et al. explored the crystal structure and synthesis methods of only tin disulfide (SnS₂), a TMD material, and provided a detailed analysis of the electrochemical performance of both pristine SnS₂ and SnS₂-based nanocomposites in SC applications.⁵³ In another review, Song et al. thoroughly examined how element doping, morphology, structure, phase, composite and hybrid configurations, and the electrolyte, impact the overall performance of 2D TMD-based SCs from the perspective of device optimisation.⁵⁴ In a subsequent review, Philip et al. examined recent progress in TMD-based compounds aimed at improving electrochemical energy storage devices, highlighting material properties, device performance, and key challenges, including stability, conductivity, and cost. They stressed the importance of optimised synthesis methods, innovative heterostructures, and advanced electrolytes to create flexible, stable, and high-performance SCs for future use.⁵⁶ Another study by Debbarma et al. reviewed the transition metal tellurides (TMTes), covering their composition, crystal structure, physical properties, and synthesis methods. They also examined factors influencing the charge storage mechanism in TMTes, the impact of morphology on electrochemical performance, and the role of various transition metal-based tellurides in SC applications.⁵⁷ Apart from these, Sowbakkiyavathi et al. reviewed the fundamentals and recent progress in SCs, concentrating on TMD materials and their synthesis methods. They underscored the role of doping with CNTs, MWCNTs, reduced graphene oxide, metal-based compounds, and polymers in enhancing electrochemical performance.⁵⁵ In a distinct review, Mohan et al. investigated tungsten disulfide-based nanomaterials, covering their structural characteristics, synthesis approaches, and an in-depth analysis of the electrochemical performance of WS₂-based electrode systems.⁵⁸ In another review, Khan et al. discussed graphene/TMSe composites and explored the synergistic effects between them, like structural stability and charge transfer kinetics. Along with this, they explored the challenges based on the graphene/TMSe hybrid SC.⁵⁹

While existing reviews on TMDs for supercapacitor applications have largely focused on specific materials or on modification strategies and interface engineering, a comprehensive understanding that connects supercapacitor fundamentals with the electrochemical performance of TMDs, particularly in light of recent progress, remains insufficiently addressed. In this context, the aim of this review is to provide an in-depth, structured, and up-to-date overview of high E_d SCs employing TMD-based electrode nanomaterials for energy storage applications. It explores the use of 2D/3D TMDs to enhance SC performance. The review begins with an in-depth explanation of SCs, covering their fundamental principles and various performance enhancement techniques. It then highlights the distinctive merits of ultrathin 2D/3D nanomaterials, focusing on their electronic and crystal structures. A variety of TMDs and their composites utilised in SCs are introduced. Subsequently, the structural parameters and inherent engineering aspects that influence capacitance performance are elaborated. Additionally, the review describes the design and future development of TMD-derived materials tailored for next-generation energy storage technologies. Finally, based on recent advancements, we conclude by offering insights into the current challenges and future outlook of this rapidly evolving field. This review serves as a valuable resource, offering a clear and concise explanation of SCs, making it accessible even to scholars with limited prior exposure to electrochemical energy storage.

2. Supercapacitor fundamentals

SCs have attracted significant interest as ESDs over the last few decades due to their ability to store and release energy quickly, providing high current in a short time.^60,61 Here, we present the historical progression of the development of SCs, as depicted in Fig. 3.⁶²

Fig. 3 Historical timeline of the development of SCs. Reproduced from ref. 4 with permission from American Chemical Society, copyright 2018.

The SCs mainly have three components: electrolytes, electrodes (positive or negative), and separators. The electrolyte can be liquid, solid, or in the gel form, and it allows ions to move for the charge–discharge process.^63–65 The electrodes store electric charge by accumulating ions from the electrolyte. A separator is employed to prevent direct contact with the electrodes.

2.1 Working principle of SCs

The principles underlying energy storage are based on two mechanisms:⁶⁶

• The EDL capacitance originates through the adsorption of coulombic charge on the interfacial region between the electrode and the electrode–electrolyte.

• Pseudo capacitance originates from surface redox reactions that are related to their respective potential.

• The combination of both forms the storage principle of hybrid SCs.

2.2 Supercapacitor classification based on charge storage mechanisms

SCs are classified into three distinct classes based on their energy-storage mechanisms, as outlined and discussed in detail below.

2.2.1 Electric double layer capacitors (EDLCs). An EDLC is considered a promising high-power energy storage solution for both electric transport and wireless communication devices.⁶⁷ EDLCs offer advantages, including higher rate efficiency and longer cycle life, compared with modern secondary batteries.⁶⁷ In EDLCs, energy is stored through the separation of charges at the interface between the electrode and electrolyte, as illustrated in Fig. 4(b). Most EDLCs use liquid electrolytes, typically consisting of aprotic solvents such as aqueous electrolytes (salts dissolved in water), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DME), or ethylene carbonate (EC).⁶⁸ These EDLC SCs store energy via electrostatic interactions in Helmholtz double layers, which develop amid the electrode–electrolyte interfaces. In addition, for EDLC SCs, graphene, activated carbon (AC), carbon nanotubes (CNTs), carbon aerogels, metal oxides, and conducting polymers are frequently employed as electrode materials owing to their large specific surface areas, which enhance capacitance.⁶⁸

Fig. 4 (a) Classification of SCs. Reproduced from ref. 4 with permission from American Chemical Society, copyright 2018. (b) Schematics of different charge-storage principles underlying EDLCs, pseudocapacitors, and hybrid SCs. Reproduced from ref. 64 with permission from Royal Society of Chemistry, copyright 2019.

2.2.2 Pseudo-capacitors. A pseudo-capacitor represents a category of SCs that fall between batteries and EDLCs. The pseudo-capacitor forms an SC when combined with a double layer.⁶⁷ It stores energy via rapid, reversible faradaic reactions (such as redox reactions, electro-sorption, or intercalation) at the electrode–electrolyte interface, as shown in Fig. 4(b). This results in a capacitance exceeding that of EDLCs, attributed to the presence of faradaic charge-storage mechanisms.⁶⁹

2.2.3 Hybrid supercapacitors. The hybrid supercapacitor is primarily governed by a combination of EDLC and pseudo-capacitor mechanisms as depicted in Fig. 4.^66,70 The ideal hybrid SCs would offer superior P_d and prolonged cycle life, along with an E_d comparable to that of batteries, as shown in the Ragone plot (Fig. 1(a)). The limitations of EDLCs are absent in pseudo capacitors, and vice versa. Their combination (hybrid SCs) overcomes the shortcomings of each individual component, resulting in enhanced capacitance. The combination offers a higher working potential and carries capacitance that is two to three times greater relative to conventional capacitors, along with EDLCs and pseudo-capacitors. Hybrid SCs are synthesised by integrating various redox and electric double-layer capacitor (EDLC) materials, including graphene, graphite, metal oxides, conductive polymers, and activated carbon.^71–73

2.3 Components of supercapacitors

A SC is composed of four primary components (Fig. 5): electrode materials, electrolytes, a current collector for charge collection, and a separator that isolates the cathode and anode, and their selection largely influences the SC performance.^74,75 To build insight into how these components affect the SC performance, we discuss each component in detail below.

Fig. 5 Different components of the SCs.

2.3.1 Electrode materials. Choosing the appropriate electrode material is essential for optimising SC performance, as it directly impacts energy storage, power delivery, and overall efficiency. The typically utilised electrode materials in SCs include (i) TMDs like molybdenum disulfide (MoS₂); (ii) porous carbon materials, like graphene, carbon nanotubes (CNTs), and activated carbon (AC); (iii) metal nitrides, like vanadium nitride (VN) and titanium nitride (TiN); (iv) metal oxides, including ruthenium oxide (RuO₂), manganese oxide (MnO₂), vanadium pentoxide (V₂O₅), and molybdenum trioxide (MoO₃); (v) other materials that have gained attention in recent years, including MXenes, conductive polymers, like polypyrrole (PPy), polyaniline (PANI), and poly(phenylene diimine) (PPdi), and conductive metal–organic frameworks (MOFs).⁶² Additionally, it is crucial to consider the material's compatibility with electrolytes, cost-effectiveness, and manufacturability. For this purpose, optimising the pore size and structure is vital, as it facilitates easier ion movement, which boosts overall efficiency. Furthermore, surface functionalization of electrode materials improves electrolyte compatibility, while the use of thin, uniform electrodes helps minimise resistance.^76–78

2.3.2 Electrolytes. The electrolyte in an SC plays a vital role in facilitating ion movement between electrodes. The electrolyte is basically composed of cations, anions, and a solvent (except in ionic liquid (IL) electrolytes), and serves as the charge transfer medium. The electrolytes can be categorised into several types: (i) basic electrolytes, including potassium hydroxide (KOH) and sodium hydroxide (NaOH); (ii) acidic electrolytes, including sulfuric acid (H₂SO₄) and hydrochloric acid (HCl); (iii) strongly concentrated electrolytes, including hydrate-melt electrolytes and water-in-salt (WIS); (iv) neutral electrolytes, such as metal sulphate salts (e.g., sodium sulphate, Na₂SO₄).⁶² Crucially, the electrolyte selection is basically determined by the required balance of performance, stability, and cost.

2.3.3 Current collectors. The current collector facilitates electronic transfer and ensures uniform charge distribution at the surface of faradaic reactions, and defines the characteristics of the SC.⁷⁹ Over the past few decades, metallic (foil and porous) and carbon-based current collectors have been widely used in SCs.⁷⁵ However, fundamental criteria for selecting current collectors apply regardless of the properties of SCs, ensuring high efficiency and stable operation.

2.3.4 Separators. In an SC, the separator maintains a uniform gap between the anode and cathode, preventing short circuits caused by direct electrode contact. It is usually a microporous film composed of polymers such as polyethylene (PE) or polypropylene (PP). It should be chemically stable and resistant to high voltages and environmental conditions to ensure longevity and safety. Its function also ensures the proper transport of ions between electrodes through the electrolyte during charging and discharging cycles.

2.4 Different parameters and their influence on the efficiency of supercapacitors

The SC performance is determined based on several key criteria including (1) high C_s, (2) significantly superior P_d, (3) relatively superior E_d, (4) excellent cycle stability, (5) rapid charge–discharge capability, (6) operating voltage, (7) equivalent series resistance, (8) time constant and (9) cost-effectiveness.^42,80 These parameters are described below:

2.4.1 Capacitance. The device's capacitance (C) is the amount of charge (ΔQ) stored per unit of applied voltage (ΔV).⁸¹

Moreover, in SCs, capacitance is typically defined in terms of specific capacitance (C_s), as:⁸²

where m represents the mass, area, or volume.

Furthermore, under constant current conditions during charging and discharging, eqn (2) can be rewritten as:⁸³

where Δt represents the discharging time.⁸⁴

2.4.2 Energy and power density. The electrochemical efficiency of SCs is primarily assessed through their E_d and P_d and can be determined using eqn (4) and (5), respectively.⁸⁵Here, ν represents the scan rate, and t represents the time span of the GCD discharge curve. Using eqn (4) and (5), the E_d and P_d were calculated via the CV method, while eqn (4) and (6) were used to calculate the E_d and P_d, using the GCD method, and these techniques are discussed in the following Section 2.5.⁴²

2.4.3 Equivalent series resistance (ESR). The combined resistance of the SC configuration, including the electrolyte, electrode, electrode-collector interface, and separator, is referred to as the ESR (R_esr) as given below.⁸⁶where I represents the current and V denotes the voltage.

2.4.4 Operating voltage (V_o). Ideal capacitors are assumed to operate without voltage limit restrictions. In contrast, real capacitors have specific upper and lower voltage limits that describe their “voltage window”. Exceeding this voltage range may trigger electrolyte decomposition, damaging the device. Capacitor electrolytes are classified into two kinds: aqueous and nonaqueous. Aqueous electrolytes are easier to grip and harmless in operation in a narrow potential window, while nonaqueous electrolytes provide a wider voltage window. Diverse SC materials can enhance the operating voltage (V_o) in asymmetric configurations by creating an electrochemical potential difference between the electrodes.⁴²

2.4.5 Time constant and cycle life. The time constant is a crucial parameter in SC performance evaluation and is determined by the SC capacitance and equivalent series resistance (ESR). It is the product of the capacitance (C_s) and ESR (R), expressed by using the formula τ = R × C_s. In practical applications, SCs are used for short-term energy bursts, with time constants typically ranging from seconds to minutes. The time constant varies based on the capacitance and ESR of SCs.⁴² Apart from this, another crucial parameter is the cycling life of the SC. The cycle life of SCs is chiefly influenced by the capacitance retention of the electrode materials. Key factors like applied voltage, operating temperature, and charge/discharge current also play a role in determining their longevity. Activated carbon electrodes, with their chemical and electrochemical stability, help extend the lifespan of SCs.⁴²

2.5 Techniques used to measure the electrochemical performance of supercapacitors

Electrochemical performance of materials is determined using two configurations: the two-electrode and three-electrode systems. Various analytical techniques, including CV, GCD, and EIS are utilised to systematically determine the performance characteristics of SCs.⁸⁷

2.5.1 Cyclic voltammetry (CV). CV is a highly advanced, pervasively utilised electrochemical procedure that comprehensively characterises a system's thermodynamic and kinetic properties.⁸⁸ It provides valuable insights into reaction kinetics, electrochemical reversibility, and diffusion-controlled transport phenomena, and distinguishes between capacitive and faradaic charge storage mechanisms. The current–potential plot, called the voltammogram, serves as a diagnostic tool for understanding electrochemical behaviour, especially in materials such as TMDs and hybrid structures.^89,90 Theoretically, the presence of a rectangular CV curve indicates ideal capacitive behaviour, while an EDLC electrode shows a distorted shape due to non-ideal behaviour. In contrast, faradaic reactions in pseudo-capacitors produce reduction and oxidation peaks. From the CV curve, a range of parameters, including C_s, E_d, and P_d, charge retention mechanisms, stability, and operational lifetime, can be calculated to evaluate the performance of SCs and other electrochemical devices.^91–93

To further analyse the electrochemical processes involved, the concentrations of redox species on the electrode surface are assessed using the Nernst equation (eqn (8)).

where E_T represents the reversible cell voltage at temperature T, E⁰ denotes the standard-state reversible cell voltage, R is the gas constant, F is Faraday's constant, C_red signifies the concentration of the reductive species, and C_ox indicates the concentration of the oxidative species.

Moreover, Randles–Ševčík eqn (9) provides a theoretical expression for the peak current in a reversible CV concerning the scanning speed, which is crucial for studying electrochemical mechanisms.⁹³ Peak current (i_p) in redox reaction cycles is influenced by several factors, including the concentration (C′), diffusion coefficient (D), scan rate (ϑ), number of electrons embedded in the redox reaction (n), electrode surface area (A) of the redox-active species and Faraday constant (F).

Calculating peak currents using this equation and plotting them against the square root of the scanning rate reveals a direct correlation, indicating that diffusion-controlled processes are the primary mechanism for charge storage.⁹⁴ Moreover, for reversible electrochemical reactions, the anodic and cathodic peak potentials can be used to determine the number of electrons involved in the electrode reaction.

Apart from these, Dunn's power law is another general formula relating the peak current to the scan rate, providing insights into the charge storage dynamics of the electrodes, as outlined in eqn (10).

i_p = aϑ^b (10)

In this equation, i_p represents the current response corresponding to a specific voltage (relative to the reference electrode), and ϑ denotes the scan rate. The diffusion and capacitive contributions are assessed via the b value, obtained from the slope of log i vs. log(ϑ); it ranges from 0.5 to 1.0 in the power-law relation. A b value of 0.5 indicates a diffusion-controlled (intercalation/deintercalation) process, while b = 1.0 reflects a capacitive-controlled current response.⁹⁵

Besides, the relative contributions of diffusion-controlled charge storage and capacitive processes (including EDLC and pseudo capacitance) might be distinguished by deconvoluting the Voltammetric current response (eqn (10)) via two mechanisms:

where the k₁ϑ and term correspond to the capacitive current, and the diffusion-limited current, respectively.

Derived from the profile of the obtained CV plot, its mechanism of charge storage, whether it is electrical double layer capacitance or pseudo-capacitance, can be predicted.⁹⁶ This prediction is mathematically supported by the relationship, as shown in the following eqn (12):

where I(t) = current response, C = capacitance (F), and .

Now to determine the C_s (F g⁻¹) of the electroactive material, eqn (12) can be modified as eqn (13), by assuming that the auxiliary electrode's capacitance is much larger than the working electrode's, due to the potentiostats enabling effective system analysis,

where is calculated by integrating the area beneath the CV, m represents the mass of the electrode material (g), ϑ denotes the scan rate (mV s⁻¹), and the voltage range (V) is ΔV. Moreover, the specific energy (Wh kg⁻¹) and specific power (W kg⁻¹) of the electrode material can be determined using the following eqn (14) and (15).⁹⁷

2.5.2 Galvanostatic charge–discharge (GCD). GCD is a critical electrochemical technique used to evaluate SC performance.⁸⁷ In a typical GCD experiment, a constant current density is applied, and the resulting potential variations are recorded with time.

The various parameters, including C_s, E_d, and P_d of an electrode material, are evaluated from the GCD curves using the subsequent eqn (16)–(18), respectively:⁶⁰

where i denotes the applied constant current (A), t represents the charge–discharge duration (s), m refers to the mass of the electrode material (g), and ΔV indicates the potential window.^94,98 Additionally, GCD provides valuable insights into other important electrochemical properties, such as:

• Rate capability: variation in capacitance at diverse current densities.

• Cycling stability: retention of capacitance over multiple charging and discharging cycles.

• Coulombic efficiency: ratio of stored charge to delivered charge during the charge–discharge cycles.

2.5.3 Electrochemical impedance spectroscopy (EIS). EIS is an operational method that yields critical insights into series resistance (R_s), charge-transfer resistance (R_ct), double-layer capacitance (C_dl), and Warburg's impedance (Z_w) due to diffusion.⁹⁹ The impedance (Z) is measured across spanning frequencies from 0.01 Hz to 1 MHz, incorporating the extent of measurement precision achievable by most EIS instruments represented by a specific value of Z (Ω).⁹⁵

Within a Nyquist plot, the real part of impedance (Z′ = Z₀(cos θ + i sin θ)) is represented along the horizontal axis, whereas the reactive component (Z″) appears on the vertical axis. This plot typically displays semicircles in the high-frequency region, indicative of faradaic redox reactions or electronic conduction.¹⁰⁰ The 45° linear segment observed at medium frequencies is indicative of molecular diffusion, commonly referred to as the Warburg region, with a 90° line observed at lower frequencies indicating the development of an electric double layer on the electrode's surface. The equivalent series resistance (R_s) is represented by the semicircle's intercept on the real axis, and charge transfer resistance (R_ct) is estimated from the low-frequency region, where a low value signifies a fast charge transfer process.¹⁰¹ Fitting the Nyquist plot using the Randles circuit model (Fig. 6(b)) allows for the extraction of additional parameters, including capacitance owing to the development of double-layer (C_dl) and Warburg's impedance (Z_w). The slope of the Warburg line in the lower-frequency area elucidates the charge storage mechanism of electrode materials. In contrast, the Bode plot represents angular frequency (ω) plotted along the horizontal axis against the shift in phase (θ = arg Z) or log impedance (log Z) along the vertical axis.¹⁰² This representation provides insights into faradaic impedance related to charge transfer and diffusional processes, enhancing understanding of the system's behaviour across different frequency ranges.¹⁰³ Faradaic impedance (R_f) related to charge transfer, along with diffusional phenomena, is examined by using the following eqn (19):

R_f = R_ct + R_w (19)

where and σ denote the Warburg coefficient (ohm rad^1/2 per s) and Warburg impedance .

Fig. 6 (a) Characteristic CV and GCD profiles for EDLCs, and pseudocapacitive, and battery-type materials, (b) schematic of a general circuit model for EIS with Bode and Nyquist plots. Reproduced from ref. 107 with permission from Wiley, copyright 2019. (c) Combining material results in asymmetric and hybrid configurations, each exhibiting unique CV characteristics. Reproduced from ref. 87 with permission from Elsevier, copyright 2023.

Theoretically, the phase shift in a Bode plot is represented as the phase angle, determined by .

For a reversible process, R_ct = 0 and the phase angle is ≤45° and for a quasi-reversible process, R_ct > 0 and the phase angle is <45°.

The capacitance of the electrical double layer, C_dl, is determined by using eqn (20):

where ω = angular frequency in units of rad s⁻¹.

Within the Nyquist plot, Warburg's impedance (Z_w) appears as a diagonal line inclined at 45°. The Bode plot shows a phase shift of 45°.¹⁰⁴ Minimal R_s and R_ct values are crucial for minimising IR drop, which enables larger output power and energy in energy storage systems. Therefore, the charge-transfer behaviour of the prepared electrodes is examined using EIS.^105,106

3. Transition metal dichalcogenides

3.1 Structural characteristics and their properties

TMDs can typically be denoted by the molecular formula, MX₂ (with M representing transition metals from groups IVB to VIII and X denoting elements such as S, Se, and Te from group VIA) (Fig. 7(a)).^51,108 Macroscopic TMDs have been extensively researched for an extended period due to their ability to create compounds with diverse electronic structures. In their bulk form, MX₂ compounds are layered materials (or van-der Waals solids) displaying significant intralayer bonding and weak interlayer bonding. Every layer of TMDs contains three atomic layers, with a transition metal atom lying within two chalcogen atoms. The chalcogen atoms are fully saturated, making them relatively non-reactive. These characteristics allow for the isolation of individual TMD layers through techniques like exfoliation or vapor deposition. When TMDs are reduced to monolayers, their properties change significantly, mainly because charge carriers are confined to two dimensions (x- and y-directions) and do not interact in the z-direction. As a result, single-layered nanosheets exhibit fundamentally different properties compared to their bulk forms, rendering them highly suitable for numerous applications in catalysis, electronics, and photonics. Moreover, this has sparked considerable interest in these materials.¹⁰⁹ TMDs feature a tunable band-gap (direct/indirect) with a structure analogous to graphite.¹¹⁰ When considering the bonding in TMDs, metal atoms (M) supply the electrons. The metal (M) atoms in TMDs usually exhibit a +4 oxidation state, while the chalcogen (X) atoms have an oxidation state of −2.¹¹¹ The characteristics of macro-TMDs span a wide range, from insulators like HfS₂ to semiconductors including WS₂ and MoS₂, true metals like VSe₂ and NbS₂ and semi-metals like WTe₂ and TiSe₂.⁴³ TMDs exist in different structural phases (Fig. 7(b)). Among them, three well-known polytypic structures arise from varying coordination geometries of the transition metal atoms: 2H (hexagonal or trigonal prismatic), 1T (tetragonal or octahedral), and 1T′ (distorted octahedral).^108,112 The stacking configurations of the X–M–X atomic trilayers also differ. In 2H-TMDs, the atomic planes follow a Bernal (ABA) stacking arrangement, while in 1T-TMDs, the stacking is rhombohedral (ABC). This variation in structure gives rise to distinct electronic properties. For instance, the 2H phase of MoS₂ exhibits semiconducting characteristics, while the 1T phase of MoS₂ demonstrates metallic behaviours.¹⁰⁸ To gain a better understanding of TMD materials, we have discussed their diverse properties below in detail.

Fig. 7 Composition and crystal phases of TMDs: (a) the composition of TMDs and (b) schematic diagrams of different TMD phases, including hexagonal (2H), octahedral (1T), and distorted octahedral (1T′). The top view shows the atomic arrangement of a single layer (top panel), while the side view depicts the typical packing sequences (bottom panel). Reproduced from ref. 108 with permission from Wiley, copyright 2023.

3.1.1 Electronic properties. The unique dispersion of electronic states across the 2D plane gives rise to many remarkable properties of 2D materials. A comprehensive description of their electronic structure often requires detailed density functional theory (DFT) calculations. However, fundamental electrical properties for TMDs can be predicted from the ligand field-induced electronic splitting of the nonbonding transition metal d-orbitals and the filling of these orbitals.¹¹³ All layered TMDs crystallise in either octahedral or trigonal prismatic coordination, with group 6 compounds typically adopting the latter in their most stable form, known as the 2H phase. In this 2H phase, the ligand field splitting of the d-orbitals results in the formation of d_z² (a1′), d_x²−y²,xy (e′), and d_xz,yz (e″) bands, which are separated by an energy gap. The two d-electrons of the transition metal fill the a1′ orbital, giving the material semiconducting properties. Octahedrally coordinated TMDs, commonly known as the 1T phase, feature degenerate d_xy,yz,zx (t_2g) and d_{z²,x²−y²} (e_g) orbitals. Group 6 TMDs are typically unstable in the octahedral coordination; however, the phase can be induced through alkali metal intercalation or high-dose electron irradiation. Since the lower-lying t_2g orbitals are only partially filled, group 6 TMDs in the 1T phase exhibit metallic electronic behaviour.¹¹³

2D TMDs show distinctive optical and electrical properties because of quantum confinement and face phenomena, notably arising from the transition of the bandgap, undergoing a transition from indirect to direct as the material is reduced to monolayers. The tunable bandgap of 2D TMDs, along with their robust photoluminescence (PL) coupled with high exciton binding energy, positioned them as optimistic materials for diverse areas of optoelectronic applications, including solar cells, photodetectors, LEDs, phototransistors, etc.^114–116 MoS₂, for example, displays inimitable assets like a direct bandgap ∼1.8 eV, high mobility (around 700 cm² V⁻¹ s⁻¹), a large current on/off ratio (∼10⁷–10⁸), significant optical absorption (∼10⁷ m⁻¹ in the visible range), and strong photoluminescence (PL) due to the direct bandgap in the monolayer. These remarkable characteristics have made MoS₂ widely studied for electronic and optoelectronic applications.¹¹⁷

3.1.2 Transport properties. The progression from 3D to 2D brings about significant changes in material properties. Key characteristics of TMD monolayers, including a stable structure, electron mobility, and bandgap, make them ideal for semiconductor fabrication. Thin-layer TMDs generally exhibit lower electron mobility than their bulk counterparts. However, this carrier mobility can be enhanced by coating the TMDs with materials such as HfO₂ and hexagonal boron nitride (hBN).⁵¹

3.1.3 Mechanical properties. The properties of TMDs are largely governed by their band gap. Monolayers of 2D materials were more challenging to deform uniformly, so AFM (atomic force microscopy) was employed for identifying mechanically exfoliated monolayer flakes without defects. For instance, MoS₂ exhibits a Young's modulus of approximately 270 GPa for monolayer flakes (200 GPa for bilayer flakes), with a strain tolerance of up to 10% before failure. As the number of layers increases, Young's modulus of multilayer flakes (ranging from 5 to 25 layers) increases to around 330 GPa. As strain increases, both the direct and indirect band gaps of the material decrease, with the indirect band gap decreasing more rapidly than the direct band gap. This results in a reduced emission efficiency in monolayer TMDs under high strain.⁵¹

3.2 Merits, demerits, and mitigation strategies

Owing to their unique properties and beneficial features, TMDs hold significant promise as electrode materials for advanced energy storage devices, such as supercapacitors.

3.2.1 Merits. (a) High specific surface area: the large specific surface area of TMDs greatly benefits their electrochemical performance. Increased surface area provides more active sites, improving ion adsorption and charge transfer, which facilitates faster ion diffusion. This directly impacts their rate capability and overall performance, particularly in monolayer TMDs where the surface area is the greatest. Thanks to their high surface area, TMD electrode materials are ideal for more efficient, high-response energy storage devices.^118–120 (b) Tunable layered structure: TMDs possess a distinctive layered architecture, with neighbouring layers held together by van der Waals forces. This characteristic enables them to rearrange their layers in response to external stimuli, facilitating safer, easier exfoliation and restacking.¹²¹ By modifying the number of layers and the interlayer distance, one can easily tune electronic conductivity, ion mobility, and mechanical properties. Typically, monolayer and few-layer TMDs offer enhanced conductivity and quicker ion transport, thereby improving supercapacitor efficiency.¹²² (c) Tunable band gap: the range of TMDs depends on their band-gap thickness and phase, due to quantum-confinement effects that enhance carrier mobility.¹²³ For example, in 2H-MoS₂, the bulk band gap is 0.88 eV, while the monolayer's band gap can reach 1.71 eV, enabling tunable indirect-to-direct band-gap transitions.¹²⁴ Meanwhile, monolayer 1T-MoS₂ exhibits metallic conductivity with a negligible bandgap, whereas the 1T′ phase features a narrow bandgap and quasi-metallic properties.¹²⁵ Hence, by varying the band gaps of TMDs, their electronic properties can be customised. (d) Chemical stability: the valence electrons of transition metals interact with the p-orbitals of chalcogens, forming a stable electronic configuration. d–p hybridisation boosts the strength and stability of the TMD crystal lattice. Consequently, TMDs exhibit consistent performance over long electrochemical cycles with little degradation, even under harsh conditions. The strong M–X bonds also provide corrosion resistance in acidic and alkaline environments, rendering TMDs ideal for energy storage applications.¹²⁶

3.2.2 Demerits. (a) Restacking of layers: interlayer aggregation and restacking hinder the energy storage of TMDs by reducing surface area and ion transport. Weak van der Waals forces cause these materials to aggregate or restack under external forces or in solution, leading to structural damage and lower performance in supercapacitors.¹²⁷ (b) Structural collapse: during charge–discharge cycling, TMDs undergo volume expansion and mechanical strain, which can damage the lattice, disrupt interlayer interactions, and lead to structural collapse, thereby affecting cycling stability.¹²⁸ (c) Low conductivity: covalent bonding between transition metals and chalcogen atoms leads to electron localisation, limiting charge delocalisation and electronic conductivity. The low conductivity of TMDs mainly results from weak interlayer bonding that restricts electron mobility and alters their electronic structure, making charge excitation or transport difficult. Defects and impurities introduced during synthesis can scatter charge carriers, further reducing conductivity.¹²⁹ (d) Susceptibility to oxidation: TMDs are prone to oxidation when exposed to air, as oxygen molecules adsorb on their surfaces, altering the oxidation state of the metal centres and accelerating oxidation. This results in oxides with poor conductivity and low electrochemical activity. The surface's tendency to adsorb oxygen alters the oxidation states of metal ions, damaging the lattice and reducing stability.^130,131

Surface modification and heterojunction engineering enhance conductivity and reduce interfacial resistance. Creating nanostructures with specific arrangements improves electron transport. Organic molecules, polymers, or chemical modifications prevent restacking. External electric or magnetic fields can alter interlayer interactions. Designing nanostructures with strong interlayer forces, like porous or heterostructures, stabilises TMDs. Surface treatments like carbon coating or doping decrease oxidation. Combining TMDs with stable materials like metal oxides or nitrides forms heterostructures or composites to further prevent oxidation. Approaches such as doping, forming composites, or using confined structures strengthen interlayer bonds and prevent degradation and collapse.^132–134

3.3 Synthesis routes for TMDs

The synthesis of TMDs typically follows two principal routes: top-down and bottom-up methods.^135–137 The bottom-up procedure involves building nanomaterials formed using atomic or molecular building blocks, which allows for precise control over their properties at the nanoscale. In contrast, the top-down method involves controlled downscaling of bulk materials to nanoscale forms, often used in top-down fabrication processes for the generation of thin sheets using diverse physicochemical processes. Each approach presents unique advantages and can be chosen according to the desired characteristics and applications of the TMDs (Table 1).^138,139

Table 1 Different synthesis methods of TMDs^a

Material	Synthesis route	Precursors	Preparative parameters	Morphologies	Ref.
a Hydro: hydrothermal, LPE: liquid-phase exfoliation, Oxi: oxidation, CVD: chemical vapour deposition, MW: microwave-assisted, TR: thermal reduction, VF: vacuum filtration, DCS: DC sputtering, Li-SE: Li-intercalation and sonication-assisted exfoliation, CBD: chemical bath deposition, Solvo: solvothermal, BM: ball milling, SCM: soft chemical method, BS-DC: bath sonication followed by dip-coating, LE: liquid exfoliation, PAS: polyquaternary ammonium salt, MSE: mixed solvent exfoliation, PEG-800: polyethylene glycol-800, VGCNF: vapor grown carbon nanofibers, T-S: target to substrate, and Soni: sonication.
FeNi2S4-g-MoSe2	Hydro	(FeCl3·6H2O, NiCl3·6H2O), thiourea, and exfoliated TMDs (MoSe2 or MoS2)	180 °C, 24 h	Hierarchical nanostructure	103
1Td WTe2	LPE	Single crystals of 1Td WTe2 (type-II Weyl semimetal)	Soni: 600 W, 8 h, cooling	Few-layer nanosheets (2–7 layers)	180
h-WO3/WS2	Oxi/CVD	WO3 nanowires	Vacuum (10^−3 mTorr), Ar, 850 °C, 20 °C min, 40 min	Nanowires	181
rGO/TMD composite papers (MoS2, MoSe2, or MoTe2)	LPE/TD/VF	TMD powders and super acids (chlorosulfonic acid and methanesulfonic acid)	Soni: 30 min, Ar (glovebox), RT	Nanosheets	182
MoS2-rGO/PGE	LPE; refluxing	MoS2 powder; rGO and aq. MoS2	Soni: 100 W, 80 kHz, 90 min; 100 °C, 6 h (reflux)	Heterostructure	183
MoS2	DCS	MoS2 and copper foil	Bias (MoS2 target), 6 cm (T-S), 45 W, 300 °C, 30 min	Nanoworms	184
1T-2H-hybrid MoS2	Solvo	MoS2 powder and n-butyllithium solution in hexane	90 °C, several h	Well-packed layered structure with wrinkles	185
Edge-oriented MoS2	CVD	Sulphur powder	200–300 °C, 50 mTorr, Ar (100 sccm), 0.5–2 h, natural cooling	Sponge-like films	186
1T-MoS2	Li-SE	Bulk MoS2 powder and n-butyllithium in n-hexane	—	—	187
MoS2	Hydro	Sodium molybdate and thioacetamide	200 °C, 24 h	Mesoporous morphology	188
MoS2	Two-step hydro	Molybdenum trioxide and thiourea	180 °C, 40 h	Uniform 3D flower-like nanostructures	189
MoS2	Hydro-PAS	Sodium molybdate and thiourea	220 °C, 24 h	Microflower	190
MoS2	SDBS assisted hydro	Ammonium molybdate tetrahydrate and thiourea	220 °C, 18 h	Nanosheets	191
Yolk–shell MoS2	Hydro	Ammonium molybdate, thioacetamide, and PEG-800	180 °C, 3 h	Microspheres	192
2D-MoS2	Hydro	Ammonium molybdate and thiourea	220 °C, 24 h	Spherical rose-flower-like structures	193
MoS2	CBD	Ammonium molybdate, sulfuric acid, and sodium sulfide	RT, 1 h	Nanoflakes	194
MoS2	Hydro	Sodium molybdate dihydrate and thioacetamide	200 °C, 24 h	Nanosheets	195
MoS2 thin film	SCM	Ammonium heptamolybdate, sulfuric acid, and thioacetamide	Water bath (303 K), 5 h	Nanograins	196
3D-MoS2	BS-DC	Ammonium tetrathiomolybdate	600 °C, 2 h, Ar (tube furnace)	Nanodots	197
1T-2H-hybridised MoS2 monolayers	Solvo	MoS2 powder; n-butyllithium	90 °C, several h	Nanosheets	185
MoS2; WS2; TiS2; MoSe2	LE	MoS2; WS2; TiS2; MoSe2 powders	Soni: 37 kHz, 40% amp., 12 h	‘Paper’ like structure for all	198
MoS2	BM	Bulk MoS2	300 rpm, 48 h	Nanosheets	199
Ex-MoS2	LE	Commercial MoS2 powder and n-butyllithium	—	Expanded layer	200
IE-MoS2 (IE = interspace-expanded)	LE	Sodium molybdate dihydrate, and thiourea	Soni: 2 h	Nanoflower	201
Freestanding MoS2 hydrogel	LE	1T phase MoS2 and sulfuric acid	—	—	202
MoS2	MSE	Bulk MoS2	Soni: 8 h	Nanoflake-like morphology	203
1T-MoS2	Hydro	Molybdenum trioxide and thioacetamide	200 °C, 12 h	Nanoflowers	204
3DG-VS2	In situ hydro	Graphene oxide, ammonium metavanadate, and thioacetamide	180 °C, 24 h	Nanosheets	205
MoS2/Mn	Hydro	MnCl2, MoO3, potassium thiocyanate, and sodium dodecyl sulphate	180 °C, 24 h	Flower-like hierarchical 3D structure	206
MoS2 nanowall/VGCNF	MW hydro	Na2MoO4·2H2O and thiourea	100 W, 200 °C, 30 min, 15 °C min	Nanowalls	207
VS2	CVD	Sulphur (S) and vanadium(III) chloride (VCl3)	600 °C, 25 min, Ar	Nanosheets (thickness 10 nm)	208

---

3.3.1 Bottom-up approach. The technique is effective for producing ultrathin, high-quality nanocomposites with large lateral dimensions, and large-scale production costs are typically low, as nanoscale materials are assembled using bottom-up processes that start from atomic or molecular sources.^135,140 The methods include hydrothermal, solvothermal, electrodeposition, sol–gel, and many more. Some of them are discussed below.
3.3.1.1 Hydrothermal method. The hydrothermal process serves as a standard technique for synthesising high-quality materials with precise control over their morphology.¹⁴¹ Conducting synthesis at high pressure and temperature in an aqueous or non-aqueous solution within an autoclave makes this method scalable, cost-effective, and effective at producing materials with fewer defects, suitable for applications in electronics, energy storage, and catalysis.^142,143 By heating a precursor solution in an autoclave, the hydrothermal method facilitates the creation of materials with diverse sizes and shapes. As shown in Fig. 8(A and B), J. Zhao et al. prepared a particular nanostructure consisting of Ni₃Se₂ nanosheets (NSs) grown on the surface of NiSe nanowire assembly (NWAs), which were successfully synthesised and deposited onto nickel foam through a one-step in situ hydrothermal approach, coupling with an electrodeposition route.¹⁴⁴ Bogale et al. synthesised MoS₂@CuCo₂O₄ with a palm-leaf morphology for a bottom-up approach and demonstrated it as a highly effective electrode for asymmetric supercapacitors, showcasing significant advancements in energy storage technology.¹⁴⁵ The hydrothermal approach is a commonly used technique for the synthesis of TMD-supported rGO heterostructures. Abdullah et al. (Fig. 8(C and D)) created a MoTe₂ supported on rGO nanocomposite using this approach, which involves a chemical reaction in a sealed container at high temperature and pressure, with water as the solvent. The morphology analysis revealed that MoTe₂ has an irregular nanoparticle structure with porous features, which enhances ion accessibility, and rGO exhibits a diffused nanosheet architecture with high surface area and flexibility. In the MoTe₂/rGO composite, MoTe₂ particles were embedded in overlapping rGO sheets, which form a conductive network and also highlight the strong bonding between MoTe₂ and rGO, showing a suitable SC performance. The presence of molybdenum (Mo) and tellurium (Te), and high carbon content from rGO can be confirmed by EDS analysis.¹⁴⁶

Fig. 8 (A) Schematic illustration of the synthesis of NiSe NAs@Ni₃Se₂ NS composites. (B) SEM images at different magnifications of (a–c) NiSe NWAs and (d) NiSe NWAs@Ni₃Se₂ NSs. Reproduced from ref. 144 with permission from Elsevier, copyright 2021. (C) Graphical illustration of a synthetic scheme for the MoTe₂/rGO nanocomposite, (D) SEM micrograph of (a) MoTe₂, (b) rGO and (c) the MoTe₂/rGO nanohybrid and (d) EDX spectrum of the MoTe₂/rGO nanohybrid. Reproduced from ref. 146 with permission from Elsevier, copyright 2023.

3.3.1.2 Solvothermal method. The solvothermal method is a popular synthesis technique where precursors like metal salts and sulfur sources are dissolved in an organic solvent (like ethanol, ethylene glycol, etc.). Now, the mixture is then heated in a sealed autoclave under elevated temperature and pressure conditions.¹⁴⁷ This process not only allows for controlled growth of nanostructures with a specific size, shape, and thickness but also enhances crystallinity and reduces impurities in the final product.¹⁴⁸ Using this method, materials generally showcased increased surface area, better conductivity, and stable morphologies, allowing their application in areas like energy storage and SCs.^143,149 Kumar et al. synthesised a Ni-MoS₂@SnS₂ flower-like nanocomposite via a facile one-step solvothermal method as shown in Fig. 9(a–d).¹⁵⁰ Karuppasamy et al. successfully synthesised a composite of iron sulfide/reduced graphene oxide (Fe₃S₄/rGO) using a standard solvothermal approach. FESEM showed that Fe₃S₄ nanoparticles possessing an average diameter of <50 nm are distributed evenly across the surface of rGO.¹⁵¹ Singh et al. synthesised a layered 2H-WSe₂ structure through a single-step solvothermal method. SEM micrographs of WSe₂ reveal a highly porous network of layered nanostructures with a 40 nm thickness of the WSe₂ nanosheets.¹⁵²

Fig. 9 (a) Scheme route of Ni-MoS₂@SnS₂, (b) FESEM image of 10% Ni-MoS₂@SnS₂, (c and d) TEM & HRTEM image of 10% Ni-MoS₂@SnS₂. Reproduced from ref. 150 with permission from Wiley, copyright 2025. (e) Characterisation of as-grown single-crystalline T-VS₂ nanosheets on SrTiO₃ (100) substrates, schematic of the CVD setup for T-VS₂ synthesis, and (f) AFM and SEM images of T-VS₂/SrTiO₃ (100), respectively; the inset shows the thickness of an individual T-VS₂ nanosheet. Reproduced from ref. 153 with permission from Elsevier, copyright 2025.

3.3.1.3 Chemical vapor deposition (CVD). CVD is a key technique for fabricating thin and high-quality layers. This method utilises vapor-phase precursors that chemically react on a heated substrate, ensuring precise deposition of material layers. In this synthesis technique, using high temperature facilitates the production of materials characterised by uniform thickness and large surface area, leading to better crystallisation and electrical efficiency while eliminating harsh chemical treatments.^135,154 Common precursors include metal oxides like MoO₃ and WO_3, along with chalcogen sources such as sulphur, selenium, and tellurium. Carrier gases like argon and nitrogen are used to transport precursor materials into the reaction zone and are often mixed with hydrogen gas to establish a reducing environment. Through precise regulation of reaction temperature (typically 600–900 °C), pressure, and gas flow rate, CVD ensures the controlled deposition of uniform and scalable layers of TMD materials. Depending on synthesis requirements, various CVDs such as atmospheric pressure CVD (APCVD), low-pressure CVD (LPCVD), and metal–organic CVD (MOCVD) are utilised.¹⁵⁵ Jin et al. thoroughly examined how various growth parameters in a CVD process influence T-VS₂ nanosheet synthesis, as shown in Fig. 9(e). They observed that lowering the growth temperature tends to increase sheet size, while higher vanadium precursor concentrations effectively control the nanosheets' thickness. Longer reaction durations can lead to nanosheet flipping. Additionally, the shape of T-VS₂ is affected by temperature, V source supply, and H₂ supply, resulting in a shift among trapezoidal, truncated triangular, and hexagonal forms. By carefully tuning these factors, a precise growth strategy for T-VS₂ can be established. SEM and AFM (Fig. 9(f)) analyses confirm the production of well-defined 2D VS₂ nanosheets with controllable size and thickness, whose morphology is influenced by growth conditions.¹⁵³
3.3.1.4 Microwave-assisted synthesis. The microwave-assisted method provides a highly efficient and rapid route for the fabrication of TMDs, which are widely used in SC applications.^156,157 This method involves dissolving metal salts and chalcogen sources in a solvent and then irradiating them with microwave radiation. The microwave energy heats the precursor materials rapidly, enabling the formation of TMDs like MoS₂ and WS₂ in less time than conventional methods, and this energy ensures the uniform heating of materials, by which the crystallinity and consistency of the TMDs can be improved. Also, this process offers faster synthesis, higher yields, and the ability to modify material properties for enhanced SC performance. Sahoo et al. presented a swift, cost-effective microwave technique to synthesise a nanocomposite composed of graphitic C₃N₄, reduced graphene oxide (rGO), and MoS₂ using ultrafast MW irradiation (see Fig. 10(A)). The FESEM image (Fig. 10(B)) reveals commercial MoS₂ with a nanoflake structure, characterised by random orientation and agglomeration. In contrast, the rGO/MoS₂ nanocomposite shows MoS₂ nanoflakes that are more ordered, mostly hexagonal, and grown on exfoliated rGO nanosheets that serve as templates. The g-C₃N₄/rGO/MoS₂ flakes appear distorted yet interconnected. These differences are due to the templating effects of rGO versus g-C₃N₄-coated rGO. The interconnected flakes on conductive nanosheets likely improve electron transport.¹⁵⁸

Fig. 10 (A) Schematic representation of the synthesis routes for GM (rGO/MoS₂) and CNGM (g-C₃N₄/rGO/MoS₂), (B) FESEM images at various magnifications of (a and b) commercial MoS₂, (c and d) GM, and (e and f) CNGM. Reproduced from ref. 158 with permission from Elsevier, copyright 2025. (C) Electrodeposition of composites, (a) particle addition to the electrolyte, (b) particle entrapment by the metal, and (c) composite coating. Particles are encircled in red. Reproduced from ref. 160 with permission from Elsevier, copyright 2022. (D) (a) Top surface FE-SEM image, (b) FE-SEM cross-sectional view, and (c and d) TEM visualisation of a prepared sample. Reproduced from ref. 162 with permission from Elsevier, copyright 2025.

3.3.1.5 Electrochemical deposition. Electrochemical deposition is an important method for fabricating TMDs for SCs. In this process, metal ions from an electrolyte are reduced and deposited onto a conductive electrode by applying an electric current, where they react with sulphur or selenium to form TMD nanostructures and films.¹⁵⁹ Here, a three-electrode system is utilised, enabling precise control over shape, thickness, and properties by adjusting parameters like voltage, temperature, and duration.¹⁶⁰ This scalable and cost-effective technique is ideal for producing materials like MoS₂ or WS₂, which enhance SC efficiency because of their excellent surface area and conductivity.¹⁶¹ Najafi et al. electrochemically deposited Mn–Ni–Co–S on annealed flexible titanium oxide (TiO₂) nanotube arrays (synthesised via anodization of titanium sheets) and ITO using CV, sweeping from −1.2 to 0.2 V at 5 mV s⁻¹ for 5 cycles in a metal nitrate–thiourea electrolyte. The synthesised sample reveals nanoflower-like formations growing on the titanium oxide nanotubes, and the close arrangement of the nanotubes and their perpendicular positioning to the substrate are indicated in the magnified cross-sectional views as depicted in Fig. 10(C)(a–c). Furthermore, TEM images (Fig. 10(D)) showed individual TiO₂ nanotubes with a straight hollow channel structure, with the wall thickness, inner diameter, and outer diameter measuring 32.98 nm, 111.1 nm, and 174.4 nm, respectively.¹⁶²
3.3.1.6 Sol–gel method. The sol–gel technique is employed to synthesise various TMDs (e.g. MoS₂), and this process involves dissolving metal precursors like ammonium molybdate and chalcogen sources like thiourea in a solvent to form a uniform solution. Then the solution undergoes chemical reactions and forms a gel, after which it is dried and subjected to heat treatment to yield materials.¹⁶³ The sol–gel method provides control over the material's composition, shape, and purity.¹⁶⁴ Materials made using this method offer a large surface area and better conductivity, along with strong electrochemical performance, making them ideal for use in SCs. It is also cost-effective, scalable, and adaptable for performance enhancement.¹⁶⁵

3.3.2 Top-down approach.
3.3.2.1 Scotch-tape method. The scotch-tape technique is recognised as the least complex and most time-effective approach for synthesising 2D TMDs.¹⁶⁶ It involves using a bulk material (e.g. MoS₂) as the starting material and peeling off sections with sticky tape.¹⁶⁷ Due to van der Waals forces, some portions stay adhered to the substrate when the tape is removed. Repeating this process produces MoS₂ flakes in various shapes, sizes, and layers.^168,169 Also referred to as micromechanical exfoliation, this method is a quick and versatile approach that allows easy transfer of single-layer MoS₂ to the desired substrate.¹⁷⁰
3.3.2.2 Liquid phase exfoliation (LPE). This process involves dispersing bulk TMD crystals into a solvent and exfoliating them using mechanical forces like sonication or high-shear mixing and leads to the formation of nanosheets or few-layer flakes, which remain stable in the liquid phase.^171,172 While liquid-phase exfoliation (LPE) can generate TMDs having good surface area as well as strong electrochemical characteristics, issues with dispersion stability and achieving high monolayer yields still exist.¹⁷³
3.3.2.3 Ball milling. Ball milling is employed as a top-down approach for synthesising nanoscale materials by grinding bulk materials with grinding media.¹⁷⁴ The mechanical forces reduce the material size, exfoliate bulk TMDs into thin nanosheets or nanoparticles, and improve the surface area, leading to better charge storage and electrical conductivity.^175,176 This scalable method enables precise tailoring of material behaviour, but challenges such as agglomeration as well as inconsistent size distribution necessitate careful optimisation of milling parameters.^177,178 As shown in Fig. 11(B), Dong et al. employed ball milling to synthesise and modify the electrode material by mechanically blending precursor components. This process uses high-energy impacts between balls and powders, ensuring thorough mixing and inducing structural changes. As a result, the material exhibited smaller particle sizes and improved homogeneity, thereby enhancing its electrochemical performance. The benefits stem from the mechanochemical effect of ball milling, which increases contact between components and modifies their structural properties. SEM analyses (Fig. 11(B)) validate the creation of a clearly defined and structurally altered material following ball milling.¹⁷⁹

Fig. 11 (A) Schematic illustration of the synthesis process of the MoS₂/FLG (FLG: few-layer graphene) composite and (B) SEM images of MoS₂/FLG@1 h, MoS₂/FLG@3 h, and MoS₂/FLG@10 h, highlighting the evolution of surface morphology with reaction time. Reproduced from ref. 179 with permission from Elsevier, copyright 2025.

4. Supercapacitors based on pristine TMDs

TMDs gained significant attention as promising electrode materials for SCs owing to their exceptional specific power, superior electrical conductivity, as well as structurally adaptable nature. Their bandgap, ranging from 0 to 2 eV, can be precisely tuned by modulating factors such as the elemental composition, atomic arrangement, and layer thickness. The adjustable nature of these materials enhances their electrochemical characteristics while also enabling the development of optimised transition architectures for high-performance energy storage applications, making them highly significant for industrial implementation. Among various nanomaterials utilised for electrochemical SC applications, both layered and non-layered transition metal sulfides (TMSs) have garnered increasing focus stemming from their widespread availability, cost-effectiveness, eco-friendliness, and elevated theoretical capacity.²⁰⁹

4.1 TiX₂ (X: S, Se, and Te)

Limited studies have explored the potential of layered TiS₂ for electrochemical SC applications despite its advantageous properties, including a fast ion transport rate, high electrical conductivity (1.4 × 10³ Ω⁻¹ cm⁻¹),²¹⁰ and remarkable theoretical capacitance (239 mAh g⁻¹ for sodium storage).^211,212 Additionally, it offers excellent stability due to its minimal volume expansion during reversible charging–discharging cycles. Ucar et al. recently produced self-standing, binder-free, electrically conductive 2D 1T-TiS₂ flakes via organolithium exfoliation. The obtained 2D structure enhanced interlayer spacing for easy intercalation and excellent conductivity, enabling binder-free self-standing films.²¹³ The single electrode exhibited a C_s of 128 F g⁻¹ at 10 mV s⁻¹. Furthermore, the symmetric SC stored 96.1% capacity after 10 000 cycles and 85.5% after 18 000 cycles. In another study, Wang et al. fabricated a new Zn-ion hybrid SC (ZHSC) using a TiS₂ battery-like anode, an AC capacitor-type cathode, and ZnSO₄ electrolyte to address challenges like slow zinc-ion diffusion and dendrite formation. The TiS₂ fragments are prepared via liquid-phase exfoliation, and Fig. 12 shows the TiS₂//AC ZHSC, which stores energy through zinc-ion intercalation in the TiS₂ anode and SO₄²⁻ adsorption on the AC cathode. It delivers a high C_s of 249 F g⁻¹, E_d of 112 Wh kg⁻¹, and P_d of 3600 W kg⁻¹, and it stores 92% C after 5000 cycles. This eco-friendly design grants access to advanced, superior energy storage systems.²¹⁴

Fig. 12 (a) Electrochemical performances of the TiS₂//AC ZHSC, (b) CV of TiS₂, the AC electrode, and TiS₂//AC ZHSC @ 5 mV s⁻¹, (c) C_s versus current density, (d) cycling performance (inset shows an LED lit by a TiS₂//AC ZHSC), and (e) Nyquist plots (inset shows the fitting equivalent circuits) of the TiS₂//AC ZHSC. Reproduced from ref. 214 with permission from Wiley, copyright 2020.

4.2 ZrX₂ (X: S, Se, and Te)

ZrS₂ is highly preferred for SCs and various other energy storage systems due to its superior stability, minimal diffusion path, enhanced electron transport capacity, abundant availability, ease of synthesis, cost-effectiveness, and ability to exhibit multiple oxidation states.^215,216 Habib et al. synthesised zirconium disulfide/diselenide (ZrX₂, X = S, Se) single crystals via the chemical vapour transport process and studied them for SC applications. ZrS₂ achieved a C_s of 18.8 F g⁻¹, while ZrSe₂ showed 18 F g⁻¹ at 10 mV s⁻¹. ZrSe₂ demonstrated robust charge–discharge endurance (>90%), and ZrS₂ benefited from higher layer spacing for better capacitance. These materials exhibit high conductivity as well as reliability, rendering them excellent candidates for SC electrodes without requiring carbon additives.²¹⁷ Using a chemical bath deposition technique, Gokulsaswath et al. fabricated zirconium disulfide (ZrS₂) quantum dots; CV analysis of ZrS₂ QDs demonstrated faradaic charge storage, evident from distinct anodic and cathodic peaks. With an increasing scan rate (5–100 mV s⁻¹), a progressive reduction in the CV area was observed, attributed to diffusion-limited ion transport, which consequently altered the electrolyte-ion dynamics at the electrode interface. Furthermore, the GCD curves of the ZrS₂ QD-based electrode show symmetric charge/discharge behaviour, signifying stable electron transport and material reliability. The faradaic process improves electron access, prolonging discharge time and leading to a C_s of 101.75 F g⁻¹ at 1 A g⁻¹, slipping to 5.11 F g⁻¹ at 10 A g⁻¹, showing strong electrochemical activity and reversibility and providing a E_d of 45.78 Wh kg⁻¹ with P_d of 14.99 W kg⁻¹. EIS analysis reveals an incomplete semicircle in the Nyquist plot, indicating pseudocapacitance with low resistance and high conductivity at high frequencies, and the material shows lower electrochemical conductivity (solution resistance is 97 Ω). Based on these findings, ZrS₂ QDs show potential for use in energy storage applications.²¹⁸

4.3 VX₂ (X: S, Se, and Te)

Metallic VX₂ stands out among TMDs owing to its excellent physical properties, including superconductivity, electrical conductivity, charge density wave, optical behaviour, and magnetism, making it an ideal candidate for applications within condensed-matter science, materials physics, and device technology.²¹⁹ Nandana et al. examined VS₂ nanosheets as an electrode material for supercapacitors and synthesised them through a single-step hydrothermal process at 220 °C for 24 hours. The resulting electrode was further tested using symmetric supercapacitors made with these VS₂ nanosheets (Fig. 13(a and b)), which exhibited a C_s of 106 F g⁻¹ at a current density of 1 A g⁻¹. This setup achieved an E_d of 34 Wh kg⁻¹ at a P_d of 800 W kg⁻¹, as shown in Fig. 13(c). Additionally, the supercapacitor retained 94% of its capacitance after 9000 charge–discharge cycles at 5 A g⁻¹ (Fig. 13(d)), demonstrating the promising potential of VS₂ nanosheets as effective electrode materials for supercapacitor applications. The improved electrochemical performance is driven by the high surface area, metallic conductivity, fast ion diffusion, and reversible redox activity of VS₂ nanosheets, which enhance charge storage and cycling stability.²²⁰

Fig. 13 (a) CV, (b) GCD, (c) Ragone plot, ans (d) capacitance retention profile for 9000 cycles at 5 A g⁻¹ of VS₂ nanosheets. Reproduced from ref. 220 with permission from Wiley, copyright 2025.

Feng et al. highlighted the potential of VS₂ as an advanced material for ultrathin, a flexible energy retention tool by introducing an innovative ammonia-assisted exfoliation technique to synthesise VS₂ nanosheets through an ultrathin structure of less than five S–V–S layers, leveraging their metallic properties and high conductivity for in-plane SC electrodes. The resulting VS₂ thin films demonstrated exceptional performance, achieving a C_s of 4760 µF cm⁻² in a 150 nm configuration with excellent cycling stability (no significant degradation after 1000 cycles).²²¹

4.4 MoX₂ (X: S, Se, and Te)

MoS₂ distinguishes itself among TMDs due to their unique physical characteristics exhibited in mono-layer, multi-layer, and restacked configurations, which can be obtained through chemical exfoliation. The surface morphology of MoS₂ nanosheets can be tailored to improve their electrochemical efficiency.²²² Nardekar et al. synthesised exfoliated MoS₂ quantum sheets (5 to 10 nm) via a salt-assisted ball-milling technique because it reduces MoS₂ size and layers more effectively than wet milling due to shear stress from NaCl crystals. It is clear that MoS₂ QDs show superior electrochemical properties compared to bulk MoS₂ due to their quasi-rectangular CV profile and minor redox peak, with the reduction in MoS₂ sheet size and layer count facilitating ion transport and intercalation, while the metallic 1T phase transition contributes to higher quantum capacitance. A flexible symmetric SC based on MoS₂ QSs fabricated with the MoS₂ QS-coated carbon cloth electrode along with PVA/H₂SO₄ electrolyte shows a C_s of 162 F g⁻¹ @ 1 mA, and exhibited high coulombic efficiency (>90%) with good rate reliability, having an E_d of 14.46 Wh kg⁻¹ @ 1 mA and 6 Wh kg⁻¹ @ 10 mA, even though P_d increased from 200 W kg⁻¹ to 2000 W kg⁻¹.²²³ Mishra et al. reported three-dimensional 2H-phase MoS₂ nanoflowers targeting SC-based applications. The 2H-MoS₂ nanoflower-derived electrodes exhibited a superior C_s of 382 F g⁻¹ @ 1 A g⁻¹ in 1 M Na₂SO₄ aqueous electrolytic solution. An asymmetric solid-state SC having 2H-MoS₂ nanoflowers or PVA-Na₂SO₄ electrolyte demonstrates an E_d of 16.4 Wh kg⁻¹ @ 0.2 A g⁻¹ and outstanding retention of 97.5% after 4000 cycles.²²⁴ Abraham et al. impregnated 5 nm MoS₂ nanodots (NDs) on a 3D nickel substrate via utilising a dip-coating technique without binder electrodes. MoS₂ NDs were synthesised through controlled sonication of MoS₂ nanosheets. The electrode showed good results, delivering a C_s of 395 F g⁻¹ @ 1.5 A g⁻¹ in a three-electrode setup. For a symmetric SC, the MoS₂ NDs exhibited 122 F g⁻¹ at 1 A g⁻¹ and 86% capacitance retention after 1000 cycles, along with a gravimetric power and E_d of 10 000 W kg⁻¹ and 22 Wh kg⁻¹, respectively.¹⁹⁷ Although research on molybdenum selenide (MoSe₂) is limited, it holds potential for superior electrochemical and energy storage properties compared to other molybdenum chalcogenides. In contrast, MoS₂ and MoO₃ have been extensively studied. MoS₂, a widely researched TMD, is favoured in energy-saving applications owing to its unique and diverse properties. While MoS₂ exhibits strong electrochemical performance, MoSe₂ is known for its better cycling stability.¹⁵ Vattikuti et al. synthesised a uniform MoSe₂ nanostructure using a microwave-assisted process, achieving a C_s of 257.38 F g⁻¹ @ 1 A g⁻¹ along with good cyclic reliability up to 5000 cycles.²²⁵ Upadhyay et al. synthesised layered 2H-MoSe₂ nanosheets (Fig. 14(a and b)) via in situ selenization and evaluated SC performance in KOH electrolyte. The MoSe₂ electrode exhibits battery-like faradaic behaviour, with Mo⁴⁺/Mo³⁺ redox transitions and K⁺ ion intercalation/extraction. Its hexagonal structure enables efficient ion diffusion, while minimal peak shifts indicate low polarisation and high reversibility. GCD measurements (Fig. 14(c)) reveal a capacity of 46.22 mAh g⁻¹ @ 2 A g⁻¹, decreasing to 30 mAh g⁻¹ at 10 A g⁻¹. An endurance test showed a 25% capacity loss after 1000 cycles, stabilising at 56.5 mAh g⁻¹ (64% of the initial capacity). Coulombic efficiency improved from 88% to 90% after 2000 cycles. EIS measurements indicated consistent resistance (∼0.85 Ω) and decreasing charge transfer resistance (R_ct), confirming efficient charge transfer. An asymmetric SC using MoSe₂ operated effectively up to 0–0.6 V and showed excellent performance, with CV curves indicating strong capacitive properties and pseudocapacitive behaviour at 10–90 mV s⁻¹. The charge–discharge curve demonstrates high reversibility, with C_s ranging from 4.1 to 0.5 F g⁻¹ at 0.5 to 1 A g⁻¹. The Ragone curve (Fig. 14(d)) reveals a maximum E_d of 184.5 mWh kg⁻¹ at 74.6 mW kg⁻¹. It maintains 22.6 mWh kg⁻¹ at 155.6 mW kg⁻¹, indicating good rate capability. Cycling stability tests (Fig. 14(e)) show a retention of 105% up to 10 000 cycles and CE increasing from 98% to 100%, confirming the strong performance and stability of the MoSe₂ SSC. These properties highlight the potential of MoSe₂ nanosheets as efficient electrodes for SCs.²²⁶

Fig. 14 (a) Crystal structure of monolayered hexagonal MoSe₂ showing the plane of Mo (blue) sandwiched in Se (red), (b) digital photograph of MoSe₂ SSC, (c) current density versus C_s estimated from GCD curves, (d) Ragone plot for MoSe₂ SSC, and (e) cyclic response & CE @ 1 A g⁻¹. Reproduced from ref. 226 with permission from Elsevier, copyright 2021. (f) Capacitance variations for MoTe₂, MoSe₂, and MoS₂ nanostructure electrodes, (g) EIS profiles of MoTe₂, MoSe₂, and MoS₂ nanostructures, (h) asymmetric device construction, (i) asymmetric capacitances for the MoTe₂ device, (j) capacitance retention profiles over 5000 continuous cycles for the MoTe₂ asymmetric device at 10 A g⁻¹ applied current, and (k) Ragone plots for the MoTe₂ asymmetric device and various reported literature results. Reproduced from ref. 227 with permission from Wiley, copyright 2022.

Bahadursha et al. synthesised MoTe₂ nanosheets (NSs) via a facile and cheap liquid-phase exfoliation method to fabricate an electrode. The MoTe₂ NSs demonstrated meaningfully enhanced electrochemical response, exhibiting a C_s of 859 F g⁻¹, over threefold that of bulk MoTe₂ (271 F g⁻¹) @ 1 A g⁻¹. The MoTe₂-based electrode additionally exhibited excellent cycling stability, retaining 92.7% of initial C_s after 1000 cycles @ 10 A g⁻¹.²²⁸ Hussain et al. studied and synthesised MoTe₂, MoS₂, and MoSe₂ nanoarrays. Fig. 14(f and g) shows that the MoTe₂ electrode achieves 416 F g⁻¹ @ 2 A g⁻¹, outperforming MoS₂ (173 F g⁻¹) and MoSe₂ (283 F g⁻¹), and retention of 97.1% respectively. An asymmetric SC device was constructed with activated carbon as the negative electrode along with MoTe₂ as the positive electrode, separated by 1 M KOH-dipped Whatman filter paper (Fig. 14(h)). The CVdemonstrates that the device has high-rate capability and consistent performance over 100 cycles at 100 mV s⁻¹, and the GCD reveals a nonlinear profile that indicates a prolonged charge/discharge span, and C_s was measured to be 138 F g⁻¹ @ 2 A g⁻¹ (Fig. 14(i)). These superior storage properties result from the unique surface nanoarray properties of MoTe₂. Additionally, the device retained 95.5% of its initial C_s after 5000 cycles at 10 A g⁻¹ (Fig. 14(j)), demonstrating better durability. E_d and P_d calculations revealed an enhanced specific energy of 49 Wh kg⁻¹ at various power levels (Fig. 14(k)). This improved performance is linked to the optimised nanoarray morphology that facilitates ion diffusion. Practical applications, including lighting different colour LEDs, confirmed the device's efficiency in accommodating electrolyte ions.²²⁷

4.5 WX₂ (X: S, Se, and Te)

Properties like superior surface areas, higher theoretical capacitance as well as surface-confined redox processes contribute to the high efficiency of 2D WS₂ TMDs, leading to materials intended for energy storage purposes.²²⁹ Owing to its distinctive structural and electrical properties, WS₂ is considered a promising candidate among 2D TMDs for next-generation electrochemical ESDs.^77,230,231 WS₂ consists of 2D covalently bonded S–W–S planes isolated through the van-der Waals gap, which is closely related to the active site for charge accumulation.²³² Additionally, WS₂ is of great interest because of the wide range of oxidation states of tungsten (W) atoms, ranging from +2 to +6, and its ability to store charge via an intercalation mechanism, making it a unique pseudocapacitive material. Mohan et al. synthesised WS₂ nanoflowers using a simple hydrothermal method and fabricated a flexible symmetric SC by depositing two 2 mg active electrodes on a carbon fabric substrate, and using a Celgard 3400 separator, and 6 M KOH electrolyte, which was then assembled in a SC test cell (EL-Cell). The CV curves shown in Fig. 15(a) suggests a mixed charge storage mechanism involving both pseudocapacitance and double-layer capacitance. Additionally, the non-ideal triangular shape of the GCD curves (Fig. 15(b)) confirms the pseudocapacitive behaviour of WS₂, driven by redox reactions. The identical C_s values of 119 F g⁻¹ from CV (20 mV s⁻¹) and GCD (1 A g⁻¹) validate the accuracy of the electrochemical data. The device retains nearly 100% capacitance after 10 000 cycles (Fig. 15(c)), ensuring long-term stability. Additionally, EIS analysis (Fig. 15(d and e)) confirms the low R_s (0.4 Ω) and R_ct (5.2 Ω), indicating good conductivity. The Nyquist plot shows capacitive behaviour, and the Ragone plot (Fig. 15(f)) shows an E_d of 10.57 Wh kg⁻¹.²²⁹

Fig. 15 (a) CV of WS₂, (b) GCD curve of WS₂, (c) cycling stability at 5 A g⁻¹ current density, (d) Nyquist plot, (e) equivalent circuit model employed to fit the Nyquist plot, and (f) Ragone plot of the flexible symmetric SC. Reproduced from ref. 229 with permission from Wiley, copyright 2021. (g) Specific capacity versus current density for different electrodes, (h) illustrative schematic of NiSe₂-200//AC HSC, (i) C_s vs. current density of the device, (j) Ragone curve, (k) cycle stability, and (l) photos related to a clock driven by a NiSe₂-200//AC device. Reproduced from ref. 233 with permission from Elsevier, copyright 2024.

Although WSe₂ features a layered atomic structure and inherently favourable electrical properties, studies on WSe₂-based SC electrodes remain relatively scarce.^234–236 Therefore, it is essential to develop an effective pathway to augment the performance of WSe₂ and strengthen its implementation in energy storage technologies.²³⁷ Sruthi et al. studied chemically modified WSe₂ monolayers using ad-atom adsorption, showing high quantum capacitance (>1000 µF cm⁻²). DFT calculations revealed that doping shifts the Fermi level and creates new electronic states near the band edge, enhancing capacitance. These results highlight the potential of WSe₂ for energy storage.²³⁸ A WSe₂ thin-film SC electrode on graphite, fabricated using DC magnetron sputtering, was investigated by Tomar et al. and unveiled a significant areal capacitance of 149.75 mF cm⁻², a 7.7-fold increase compared to that of bare graphite, with 86.15% retention after 2000 cycles. Using 1 M Na₂SO₄, the symmetric SC achieved an areal E_d of 5.54 mWh cm⁻² and a P_d of 1197 mW cm⁻².²³⁹

4.6 CoX₂ (X: S, Se, and Te)

Octahedron-shaped CoS₂ crystals were fabricated by Xing et al. through a simple hydrothermal process. These crystals exhibit a C_s of 236.5 F g⁻¹ @ 1 A g⁻¹ along with admirable cycling reliability, retaining 92.6% of C_s after 2000 cycles.²⁴⁰ Furthermore, Ren et al. directly synthesised metallic CoS₂ nanowires (NWs) on current collectors like carbon cloth or graphite discs. Electrochemical responses were investigated using the three-electrode setup with KOH serving as electrolyte. CV and GCD revealed that CoS₂ NWs on carbon cloth and graphite discs, respectively, particularly on graphite discs, demonstrate strong potential as high-performance SC electrodes, offering high capacitance, stable charge–discharge performance, and improved electrolyte infiltration due to their open structure. CoS₂ nanowires on graphite discs gain a higher C_s 828.2 F g⁻¹ than CoS₂ nanowires on carbon cloth with a C_s of 174.1 F g⁻¹ at 10 mV s⁻¹ and exceptional cycling stability, with minimal capacity loss (0–2.5%) after 4250 cycles @ 5 A g⁻¹. Ragone plots revealed good rate performance, with an E_d of 7.2 Wh kg⁻¹ @ 0.18 kW kg⁻¹ or 5.0 Wh kg⁻¹ @ 0.16 kW kg⁻¹ for CoS₂ NWs on graphite discs. The relatively low E_d is attributed to the small potential range limited by the aqueous electrolyte, with higher E_d potentially achievable with organic solvents.²⁴¹ Han et al. developed CoSe₂ quantum dots with selenium vacancies and hollow cages using MOF templates. The optimised structure enhances active sites, reduces volumetric expansion, and improves electroactivity. The CoSe₂/NC-350 electrode shows 12.13 F cm⁻² capacitance at 2 mA cm⁻², 90.6% retention up to 5000 cycles, an an E_d of 0.581 mW cm⁻² with 92.74% retention after 10 000 cycles.²⁴² CoTe₂ nanoflowers (NFs) were prepared by Mao et al. by utilising a simple solvothermal method. Their 20 nm thickness enhances exposure to the electrolyte and improves ion/charge movement. The CoTe₂ NF electrode demonstrates an admirable electrochemical capacitance of 460 F g⁻¹ @ 1.5 A g⁻¹ and retains 91% C_s after 5000 cycles, demonstrating good durability.²⁴³

4.7 NiX₂ (X: S, Se, and Te)

NiS₂ hollow nanoprisms produced by Dai et al. via a cost-efficient sacrificial template technique, offer efficient ion and electron pathways due to their unique hollow structure. The prisms achieved a high C_s of 1725 F g⁻¹ @ 5 A g⁻¹ & 1193 F g⁻¹ @ 40 A g⁻¹ with LiOH electrolyte, with exceptional cycling stability, showing a 22.9% capacitance increase after 10 000 cycles.²⁴⁴ NiS₂ microflowers fabricated by Dai et al. using hydrothermal and sulphidation processes, feature a unique nano/microstructure with superior conductivity. They delivered capacities of 813 C g⁻¹ @ 1 A g⁻¹ & 580 C g⁻¹ @ 20 A g⁻¹ in LiOH, retaining 93% capacity up to 10 000 cycles. A hybrid SC composed of NiS₂ microflowers and activated carbon achieved an E_d of 39.8 Wh kg⁻¹ @ 900 W kg⁻¹.²⁴⁵ Arul et al. synthesised hexapod-like nickel diselenide (NiSe₂) structures via the hydrothermal method and studied SC electrode materials for the first time. Characterisation confirmed the orthorhombic phase of NiSe₂ in the synthesised structures. The NiSe₂ electrode on graphite foil unveiled a C_s of 75 F g⁻¹ @ 1 mA cm⁻², also showing excellent cycling stability with 94% capacitance retention after 5000 cycles. The data reveal the potential of hexapod-like NiSe₂ serving as a prospective option for energy storage applications.²⁴⁶ NiSe₂ single crystals with a truncated cubic morphology were fabricated by Wang et al. and deployed as an electrode material in SC systems. The NiSe₂ electrode shows a C_s of 1044 F g⁻¹ @ 3 A g⁻¹ (4.07 F cm⁻²) and admirable current rate tolerance (601 F g⁻¹ @ 30 A g⁻¹). An asymmetric SC based on NiSe₂//activated-carbon achieved an E_d of 44.8 Wh kg⁻¹ @ 969.7 W kg⁻¹, along with 87.4% retention later 20 000 cycles, showing great potential for practical applications.²⁴⁷ Porous NiSe₂ nanowires (NWs) were synthesised by Li et al. by treating α-Ni(OH)₂ NWs with Se powder and among the investigated electrodes, NiSe₂-200 exhibited superior CV area, demonstrating the best energy storage behaviour. The CV profile of NiSe₂ NWs at various sweep rates shows consistent shapes and excellent charge/discharge stability, whereas the GCD displayed nonlinear characteristics, indicating Faraday reactions for energy storage and good charge/discharge reversibility. NiSe₂-200 showed a superior discharge time at 1.0 A g⁻¹ and achieved a C_s of 653.3 C g⁻¹ at 0.25 A g⁻¹, maintaining 408.0 C g⁻¹ at 10 A g⁻¹ (Fig. 15(g)), with a 62.5% capacity retention rate. The decrease in C_s at high current densities is ascribed to the electrode's internal resistance and underutilisation of electroactive materials. Fig. 15(h and i) shows that the NiSe₂-200//activated carbon hybrid SC showed excellent performance, including 88.3 F g⁻¹ C_s, 35.4 Wh kg⁻¹ E_d, and 74.6% retention after 21 000 cycles.²³³ Zhang et al. synthesised hollow NiTe₂ nanotubes through a low-cost hydrothermal method and evaluated them for SC applications. Their unique hollow structure, rich in defects, provides an extensive surface area coupled with effective ion transport channels, enhancing electrochemical performance. The nanotube electrodes display a superior C_s of 566 F g⁻¹ at 1.5 A g⁻¹ with admirable stability, rendering them attractive materials for energy storage systems.²⁴⁸ Nickel telluride nanorods (NiTe NRs) produced by Manikandan et al. through the hydrothermal technique using ascorbic acid acting as a reducing agent and CTAB as a surfactant, exhibit a hexagonal structure with excellent properties. Electrochemical measurements revealed a high C_s of 618 F g⁻¹ @ 1 A g⁻¹ as well as notable cycling, retaining 75% of capacitance after 5000 cycles with a CE above 99%. The marked conductivity, porous structure, and nickel's synergistic effects contribute to the superior performance.²⁴⁹

5. Supercapacitors based on modified TMDs

5.1 Doped TMDs

The incorporation of dopants into a material induces significant changes in its structural framework and physicochemical properties. Doping generally occurs through two primary mechanisms: substitutional and interstitial doping. In the substitutional doping process, dopant atoms directly replace host lattice atoms. The success of substitution depends on key factors such as the similarity in atomic or ionic radii, matching valence states, and the compatibility of coordination environments between the dopant and host atoms. In the interstitial doping mechanism, dopant atoms occupy the interstitial voids embedded in the crystal lattice instead of replacing existing atoms. This alters the material's electronic as well as structural properties while maintaining the overall lattice framework.²⁵⁰ Doping is a fundamental technique for tailoring the electronic properties of semiconductors by precisely regulating charge carrier concentration, shifting the Fermi level position, and amending the band gap energy. The controlled incorporation of dopants enables the fabrication of semiconductors with specific conductivity types (P-type or N-type), which is essential for optimising their efficiency in advanced electronic and optoelectronic applications.⁴²

Hence, by doping in an SC, one can increase conductivity and surface area and attain improved structural stability as well as ion mobility. Vikraman et al. doped transition metals (Ni, Cu, and Fe) within the MoS₂ nanoarrays by facile chemical precipitation and found that highly porous structured Cu doped MoS₂ nanostructures show better performance for SCs by achieving a maximum C_s of 353 F g⁻¹ at 1 A g⁻¹ current density along with a remarkable retention of ∼94% later 5000 cycles. Furthermore, symmetric devices with Cu doped MoS₂ electrodes achieved a specific energy of 5.58 Wh kg⁻¹ at 6 kW kg⁻¹ specific power, maintaining 94% of their initial symmetric capacitance after 5000 cycles.²⁵¹ Doping MoS₂ with transition metals, for instance Ni, Cu, and Fe, activates additional active sites, enhancing its electrochemical performance for SCs. The doping modifies the morphology, resulting in vertically aligned nanoarrays with an expanded surface area and enhanced exposure of active edges. Overall, doping enhances conductivity, surface area, and both catalytic (for the HER) and capacitive performance (for SCs).²⁵¹ Furthermore, Kour et al. showed the consequence of Cr doping in MoS₂ suggesting that due to the superior conductivity offered by Cr atoms (because it has the highest number of unpaired valence electrons among all the 3d transition metals), the hybrid SC made out of this electrode, CrMoS₂//AC, shows an impressive E_d and P_d of 40.14 Wh kg⁻¹ and 2.4 kW kg⁻¹, respectively. It demonstrated outstanding stability, retaining 83% of its capacity after 6000 cycles.²⁵² Bello I. T. et al. synthesised non-modulated cobalt doped molybdenum sulfide (MoS₂) nanoflowers through a facile hydrothermal method. The electrode materials underwent electrochemical evaluation to determine their energy storage efficiency. The materials display a C_s of 164 F g⁻¹ at 1 A g⁻¹. Also, the energy and P_d are 3.67 Wh kg⁻¹ and 3279.97 W kg⁻¹, respectively.²⁵³ Isacfranklin et al. doped MoS₂ with neodymium and gadolinium (lanthanide metals) and found that sheet-like Gd doped MoS₂ nanostructures unveiled the maximum 357 F g⁻¹ @ 10 mV s⁻¹ C_s from CV and 231.38 F g⁻¹ @ 1 A g⁻¹ as revealed by GCD analysis with an extended cycling life of 81.5% over 5000 cycles.²⁵⁴ Singha et al. showed that a SC electrode made of low-Mn incorporated MoS₂ nanoflowers exhibits a maximum C_s of 430 F g⁻¹, an E_d of 48.9 Wh kg⁻¹, and a P_d of 5 kW kg⁻¹. It also exhibits excellent capacitance retention over 5000 cycles at 10 A g⁻¹. Additionally, its performance was validated by lighting four LED bulbs in series, displaying an extended discharge time.²⁰⁶

Similarly, Shree Raj et al. demonstrated how Mn incorporation improves the electrochemical charge storage capacity of VSe₂ sheets. For this synthesis, a one-pot hydrothermal reaction is used, and it was found that 6% Mn doped VSe₂ exhibited enhanced energy storage properties, with a C_s of 250 F g⁻¹ at 1 A g⁻¹. An asymmetric SC using 6% Mn VSe₂ and red phosphorus as electrodes achieved 21.3 Wh kg⁻¹ E_d and 25.6 kW kg⁻¹ P_d, with 95% capacitance retention after 5000 cycles. Mn doping in VSe₂ boosts its electrochemical performance by superior active sites, enhancing ion transport, and preventing structural collapse. This results in smaller grain sizes and thinner sheets, which, in turn, increase surface area. However, Mn concentrations higher than 6% can impair performance. 6% Mn doped VSe₂ demonstrates the best performance, combining these effects to provide enhanced charge storage and cycling stability.²⁵⁵ Two samples using magnetron sputtering, Type I (WS₂ directly sputtered on nickel foam) and Type II (WS₂ with a 150 nm chromium (Cr) interfacial layer between WS₂ and nickel foam), were fabricated by Iqbal et al., and then electrochemical testing was conducted through CV, GCD, and EIS in three- and two-electrode setups. Fig. 16(a–d) confirms that the addition of the Cr layer significantly enhanced performance, with Type II achieving a higher specific capacity (1600 C g⁻¹ vs. 661.79 C g⁻¹ for Type I), better capacity retention (83.04% vs. 61.37%), and lower resistance (ESR: 0.1 Ω). By taking Type II as a positive electrode and AC as a negative electrode, a hybrid SC (WS₂/Cr//AC) (Fig. 16(e)) was prepared, which delivered an E_d of 81 Wh kg⁻¹, with a P_d of 1750 W kg⁻¹, and maintained 87.3% capacity after 5000 cycles as shown in Fig. 16(f–h). So, introducing the Cr layer enhances conductivity and energy storage performance.²⁵⁶

Fig. 16 (a) Specific capacity of WS₂ and WS₂/Cr through GCD. (b) Nyquist plots of WS₂ and WS₂/Cr. (c and d) Stability of both samples, (e) schematic of the real device, (f) specific capacity of the real device through GCD, (g) E_d and P_d of WS₂/Cr//AC, and (h) capacity retention of WS₂/Cr//AC. Reproduced from ref. 256 with permission from Elsevier, copyright 2024. (i) C_s of pure and Mn doped WSe₂, (j) E_d and P_d of pure and Mn doped WSe₂, (k) EIS, (l) CV stability of Mn doped WSe₂, and (m) chronoamperometry of WSe₂ pure and Mn doped WSe₂. Reproduced from ref. 237 with permission from Elsevier, copyright 2024.

Furthermore, doping of Mn into WSe₂ was done by Faisal et al. via a hydrothermal technique. Mn doped WSe₂ has enhanced electrochemical performance due to higher C_s, improved ion intercalation, and better ionic conductivity, leading to a high C_s of 1908 F g⁻¹ at 1 A g⁻¹, surpassing pure WSe₂ (593 F g⁻¹) as shown in Fig. 16(i). As shown in Fig. 16(j), the electrode showed an E_d of 210 Wh kg⁻¹, P_d of 846 W kg⁻¹, and stability after 5000 cycles, respectively. Mn doped WSe₂ has a lower charge transfer resistance (R_ct = 0.1 Ω) than pure WSe₂ (R_ct = 0.18 Ω) (Fig. 16(k)), suggesting enhanced charge transport and ion diffusion at the electrode–electrolyte interface. Fig. 16(l) illustrates that Mn doped WSe₂ retained its redox activity with negligible structural changes even after 5000 CV cycles. Fig. 16(m) presents chronoamperometry results showing that Mn doped WSe₂ maintained stable performance over 45 hours, whereas pure WSe₂ experienced a slight decline in stability. These results make Mn doped WSe₂ a promising material for efficiency and durability.²³⁷ Samal et al. illustrated a convenient method for defect engineering by incorporating transition metals, which helps to generate active sites that are efficient. For which synthesised Metal (Mn, Zn, Cr, Fe, Ni) doped CoSe₂ samples were investigated. The electrochemical performance of the asymmetric SC was first tested in a three-electrode system, and then in a two-electrode setup using different metal doped cobalt selenides as the positive electrode and titanium carbide (Mxene) as the negative electrode along with a PVA/KOH gel electrolyte with a maximum potential window of 1.5 V. The gravimetric capacitance values reported were 38.4 F g⁻¹ for pristine, and it increased to 92.11 F g⁻¹ for iron doped systems (a 2-fold increase), with the values being 73.38 F g⁻¹ for manganese, 86.87 F g⁻¹ for nickel, 49.33 F g⁻¹ for zinc, and 42.65 F g⁻¹ for chromium doped systems. Impedance analysis showed the best device had a low impedance of 2 Ω, indicating excellent conductivity. The Ragone plot and cycling stability verify that the E_d achieved was 28.78 Wh kg⁻¹ at a P_d of 778.6 W kg⁻¹ and 5000 cycles at 10 A g⁻¹ revealed a capacitance decay to 90.56% and a coulombic efficiency of ∼97.86%. Overall, the use of MXenes as the negative electrode improved performance, expanded the potential window, and enhanced stability, while doping provided active sites and robustness to the materials.²⁵⁷ Sial et al. prepared cobalt doped NiVSe via a solvothermal method on a nickel foam substrate. The material exhibited an exceptional specific capacity of 2863.38 mAh g⁻¹ at 3 A g⁻¹, along with a high E_d and P_d of 38.73 Wh kg⁻¹ and 1909.788 W kg⁻¹, respectively. It exhibited remarkable stability, retaining its capacitance over 10 000 cycles.^206,258,259 Mahajan et al. demonstrated a superior performance SC based on biocarbon-supported MoS₂ (Bio-C/MoS₂) nanoparticles synthesised via a simple hydrothermal method utilising date fruits. They reported high C_s for this carbon-based nanocomposite, derived through pyrolysis of agricultural biowaste, highlighting its potential as a cost-effective energy source. The biocompatible Bio-C/MoS₂ nanospheres showed a superior capacitance of 945 F g⁻¹ at a current density of 0.5 A g⁻¹ and demonstrated admirable cycling stability, retaining 92% of their capacitance after 10 000 charge/discharge cycles. Additionally, the Bio-C/MoS₂ nanospheres exhibited an outstanding P_d ranging from 3800 to 8000 W kg⁻¹ and an E_d between 74.9 and 157 Wh kg⁻¹. These results offer a promising pathway for the development of eco-friendly materials for high-performance energy storage technologies.²⁶⁰ Kishore et al. introduced an innovative method for developing high-performance SCs by using a banana peel, an eco-friendly and affordable biomass waste, as a precursor for heteroatom doped carbon (H-PC) electrodes. The electrochemical performance of MoS₂@H-PC exhibits notable faradaic reactions and electrostatic adsorption, resulting in an outstanding C_s of 408 F g⁻¹ at a current density of 1 A g⁻¹. Furthermore, the composite demonstrates exceptional cycling stability, maintaining 90% of its capacitance after more than 10 000 cycles.²⁶¹ Vikraman et al. arranged an asymmetrically SeMoTe layered structure, synthesised via a one-pot reaction, demonstrating that the SeMoTe electrode achieves a symmetric capacitance of 367 F g⁻¹ at 1 A g⁻¹, with an E_d of 41.3 Wh kg⁻¹ at a P_d of 4.0 kW kg⁻¹.²⁶²

Various studies indicate that doping TMDs, such as MoS₂ and WSe₂, is employed not only to enhance electrochemical performance but also to enable deep modifications. Dopants alter the charge distribution by transforming inactive sites into active ones and can modify the shape and structure of the materials. However, the efficacy of a particular dopant depends on the specific material and context. For instance, Mn doping in MoS₂ and WSe₂ improves redox behaviour; however, at certain concentrations, elements such as Fe and Co, and rare earth metals like Gd and Nd influence conductivity and structural attributes differently, owing to their electronic properties. Doping can also induce changes in the electronic structure: the d-band shifts toward the centre, and the density of electron states near the Fermi level increases, facilitating electron mobility. Additionally, interlayer spacing enlarges, easing ion movement and promoting the formation of multiple oxidation states. During this process, nanosheets become thinner, which may lead to the formation of nanoflowers. Nevertheless, increased doping concentration can introduce instability in morphology, reduce conductivity, or alter the original phase of the material. To mitigate such issues, hybrid approaches such as interfacial doping, exemplified by surface doping with chromium and the utilisation of bio-carbon scaffolds, have been proposed, allowing similar improvements without compromising the crystal structure. Substantial doping is thus not the sole solution. These insights underscore the necessity for a sophisticated system to identify the optimal dopant for each TMD, considering factors such as band alignment, defect tolerance, and dopant-host compatibility. Future research should extend beyond experimental investigations to incorporate theoretical models, thereby developing a comprehensive understanding that cohesively bridges diverse observations.

5.2 Different composites with TMDs

5.2.1 Carbon/TMDs. Carbon-based materials predominantly store charge via the electric double layer mechanism. Carbon nanotubes (CNTs) are valued for their high conductivity and stability, and the integration of nanostructures with multi-walled CNTs (MWCNTs) provides robust electrochemical activity. The combination of TMDs with conductive carbon materials (such as CNTs or graphene) increases surface area and facilitates charge transfer, thereby improving electrochemical performance. Graphene, characterised by its high surface area and excellent conductivity, serves as an ideal medium for electron transport. Nonetheless, addressing issues related to restacking and low intrinsic conductivity through the development of TMD-carbon hybrid materials remains an effective strategy.^263,264 Nabi et al. synthesised TiS₂/g-C₃N₄ and achieved a high C_s of 546 F g⁻¹, outperforming TiS₂ due to its smaller size, extra active sites, and synergistic effects. It also retained 87% of its capacitance after 2500 cycles, showcasing admirable stability. This makes TiS₂/g-C₃N₄ a promising material for SC electrodes with enhanced charge transfer and durability.²⁶⁵ Tang et al. prepared sodium-ion capacitors (SICs) using carbon-coated TiS₂ nanosheets (TiS₂@C_pvp) to deliver excellent performance due to their ultrathin structure and carbon modification. They achieve 448 mAh g⁻¹, a superior retention (387 mAh g⁻¹ @ 10 A g⁻¹), and also 92.5% retention after 5000 cycles. Combined with an activated carbon cathode, the SIC offers an E_d of 101.7 Wh kg⁻¹ with P_d of 200 W kg⁻¹, demonstrating potential of 2D hybrid materials for advanced energy storage.²⁶⁶ Iqbal et al. developed chromium sulfide and rGO-based supercapacitor electrodes and examined their structure, morphology, and electrochemical properties. Both materials display pseudocapacitive behaviour in CV curves, with a maximum C_s of 522.84 F g⁻¹ and 3.77 F g⁻¹ at 5 mV s⁻¹. GCD results reveal chromium sulfide's capacitance of 710.90 F g⁻¹, an E_d of 24.68 Wh kg⁻¹ at 3 mA cm⁻², and a P_d of 1028.81 W kg⁻¹ at 6 mA cm⁻². An asymmetric system combining chromium sulfide and rGO exhibits pseudocapacitive traits, with a CV C_s of 24.53 F g⁻¹ at 10 mV s⁻¹ and a GCD capacitance of 26.41 F g⁻¹ at 4 µA cm⁻². Its P_d of 780.35 W kg⁻¹ demonstrates its potential for supercapacitor applications.²⁶⁷ Hence, integrating chromium sulfide nanoparticles with a conductive rGO network boosts charge transport, provides electroactive sites, and improves stability. This leads to higher capacitance, power, and cycling durability in supercapacitors. Furthermore, Rana et al. demonstrated a straightforward hydrothermal method to synthesise reduced graphene oxide (rGO)-wrapped chromium sulfide (rGO/Cr₂S₃/NF). The rGO/Cr₂S₃/NF nanocomposite has a C_s of 2563.12 F g⁻¹ from CV curves at 5 mV s⁻¹, with an E_d of 87.50 Wh kg⁻¹ and a P_d of 1607.14 W kg⁻¹ at 2.0 mA cm⁻². It remains stable over 1000 cycles thanks to the excellent electrical conductivity of rGO between the porous Ni foam collector and Cr₂S₃.²⁶⁸ The author states that the rGO/Cr₂S₃/NF nanocomposite's porous structure as a binder-free electrode improves electrolyte diffusion and boosts electrochemical performance. Both studies emphasise the synergistic benefits of rGO and chromium sulfide. Nevertheless, the binder-free, directly grown structure on nickel foam greatly surpasses standard composites by offering improved charge transport, lower resistance, and better electrochemical performance. A cost-effective sonochemical technique is used by Imtiaz et al. to fabricate the ZrS₂@rGO nanohybrid. The electrochemical results for the three electrodes show that ZrS₂@rGO nanohybrids outperform ZrS₂ alone, offering C_s 1011.4 F g⁻¹ @ 10 mV s⁻¹ and 351.8 F g⁻¹ @ 40 mV s⁻¹. This excellent performance is due to the synergistic effects of sulfides and rGO, which improve ion diffusion and slow faradaic reactions. At 40 mV s⁻¹, 81% of the charge is retained. Additionally, the GCD of the ZrS₂@rGO composite shows a C_s of 1237.9 F g⁻¹ @ 1 A g⁻¹, well beyond the ZrS₂ C_s of 813.5 F g⁻¹. This demonstrates good durability, and 57.89% retention up to 10 000 cycles at 3 A g⁻¹. These outcomes position it as a viable material for superior-performance SC application. Furthermore, the ZrS₂@rGO composite shows excellent electrochemical performance in a symmetric SC, giving C_s of 274.99 F g⁻¹ @ 10 mV s⁻¹ and C_s of 327.57 F g⁻¹, and also attains a 16.86 Wh kg⁻¹ E_d at a P_d of 303.5 W kg⁻¹.²⁶⁹ Haider et al. reported a high-performance on-chip micro-supercapacitor using pyrolysed carbon/vanadium disulfide (C/VS₂) microelectrodes. Fabricated through photolithography and pyrolysis, Fig. 17(a and b) shows a comparative analysis of CV and GCD curves of C/VS₂-MSC and C-MSC. The layered VS₂ nanosheets embedded in carbon enhance ion diffusion and charge storage, yielding a volumetric capacitance as high as 86.4 F cm⁻³ (Fig. 17(c)), revealing admirable cycling stability, and retaining 97.7% of their capacitance after 10 000 cycles (Fig. 17(d)). The MSC also has an E_d of 15.6 mWh cm⁻³, with a P_d of 2.88 W cm⁻³ within a wide potential window (0–1.2 V) as shown in (Fig. 17(e)). This approach showcases the potential of layered TMDs for compact and efficient energy storage applications.²⁷⁰

Fig. 17 (a and b) Comparative analysis of CV and GCD measurements of C/VS₂-MSC and C-MSC, (c) specific volumetric capacitances of C/VS₂-MSC and C-MSC at various current densities, (d) EIS of C/VS₂-MSC and C-MSC, inset shows the Nyquist plot in the higher-frequency region, (e) cycling performance of C/VS₂-MSC @ 0.5 V s⁻¹, (f) Ragone curve of the C/VS₂-MSC, and comparative analysis with different reported devices. Reproduced from ref. 270 with permission from [Elsevier], copyright [2020]. (g) CV curves at 50 mV s⁻¹, (h) GCD curves at 1 A g⁻¹, (i) EIS curves of CoS₂@C and Co₃S₄@C, (j) schematic diagram of the asymmetrical SC, (k) CV curves of CoS₂@C//RGO in different potential ranges at 50 mV s⁻¹, (l) CV curves of the CoS₂@C//RGO device, (m) GCD curves of CoS₂@C//RGO, and (n) cycling performance & CE of CoS₂@C//RGO. Reproduced from ref. 271 with permission from Elsevier, copyright 2023.

The study by Koudahi et al. developed hybrid electrodes combining 3D graphene-like (3DG) and VS₂ to enhance E_d in electrochemical capacitors (ECs). By reducing electrode roughness, optimising VS₂ content, and using a specialised electrolyte, the cell achieved a wide operating voltage of 1.8 V. It demonstrated 80% retention up to 7500 cycles with an E_d of 18 Wh kg⁻¹ @ 430 W kg⁻¹, and 12 Wh kg⁻¹ at 31 000 W kg⁻¹. The hybrid EC offers stable, high-performance energy storage with rapid charge/discharge capability, making it ideal for advanced energy storage applications.²⁰⁵ Tobis et al. reported a hydrothermal 1-cysteine-assisted synthesis method for producing two MoS₂-based composites using distinct carbon materials: multiwalled carbon nanotubes (NTs) and carbon black (Black Pearl-BP2000). MoS₂ nanolayers were deposited onto these carbon materials, and the resulting composites were utilised as electrode materials in symmetric electrochemical capacitors (ECs). Their electrochemical performance was assessed and compared to that of the pristine carbon substrates. Among the two, the NTs/MoS₂ composite exhibited superior electrochemical characteristics, achieving a C_s of 150 F g⁻¹, attributed to enhanced conductivity and charge storage. In comparison, the BP2000/MoS₂ composite achieved 110 F g⁻¹ at a current density of 0.2 A g⁻¹.²⁷² Kapse et al. analysed 2H, 1T, and 1T′ phases of MoS₂ and their carbon-based heterostructures as SC electrodes via utilising density functional theory. The underlying CNT drives a phase transition from 1T to 1T′ in MoS₂, resulting in a high quantum capacitance (500 µF cm⁻² at 0.6 V) because of increased DOS around the Fermi level. Nitrogen doping along with defects in CNTs further enhances capacitance over a wider potential range, making 1T′-MoS₂/N doped CNT a promising electrode for next-generation SCs.²⁷³ Using a 3D rGO hydrogel network, Magdum et al. engineered a superior-performance SC electrode with VS₂ and WS₂ nanoparticles, synthesised via two routes (V-W-1 with ammonium metavanadate and V-W-2 with VS₂), followed by hydrothermal and chemical reduction to form rGO/VW hydrogels. The rGO-VS₂-WS₂ hydrogel showed superior C_s (220 F g⁻¹ at 1 A g⁻¹), E_d (30.55 Wh kg⁻¹), and P_d (355 W kg⁻¹) compared to rGO and rGO-VS₂. The uniform anchoring of VS₂ and WS₂ nanoparticles on rGO improved conductivity, ion transport, and electrochemical utilisation, enabling excellent performance and stability.²⁷⁴ Lin et al., using a simple chemical method, developed an rGO-MoS₂-WS₂ heterostructure for SCs. The composite showed a C_s of 365 F g⁻¹ @ 1 A g⁻¹, superior to that of single TMD-based materials, due to improved conductivity, lower resistance, and the synergistic effects of MoS₂, WS₂, and rGO. Operating as the positive electrode in an asymmetric SC along with rGO as the negative electrode, it achieved an E_d of 15 Wh kg⁻¹ at a P_d of 373 W kg⁻¹ and retained 70% capacitance over 3000 cycles, demonstrating superior performance and stability for SCs.²⁷⁵ Wei et al. prepared CoS₂@C and Co₃S₄@C nanoparticles using a ZIF-67 precursor through calcination and sulphuration. The CV curves (Fig. 17(g)) and GCD curves (Fig. 17(h)) demonstrate that CoS₂@C outperforms Co₃S₄@C, with a larger integral area, better redox reversibility, longer charge/discharge times, and higher capacitance, giving an inimitable hierarchical structure that enhances the surface area and active sites. CoS₂@C gives a high C_s 1151 F g⁻¹ @ 1 A g⁻¹, and also retained 85.58% capacity after 10 000 cycles, respectively. Fig. 17(i) shows the EIS curves of both electrodes. For an asymmetric SC with redox graphene (RGO) for the negative electrode and CoS₂@C for the positive electrode in a 2 M aqueous KOH solution (Fig. 17(j)), CV tests (Fig. 17(k)) showed no significant polarisation or shapeshift in the 0–1.6 V voltage window, indicating stability. The CV profiles obtained at different scan rates (Fig. 17(l)) revealed the excellent redox activity of CoS₂@C, with observable redox peaks. GCD curves (Fig. 17(m)) showed a C_s of 130.6 F g⁻¹ at 1 A g⁻¹ and 87.8 F g⁻¹ at 10 A g⁻¹. The device demonstrated an E_d of 46.52 Wh kg⁻¹ at 800 W kg⁻¹ and 33.28 Wh kg⁻¹ at 6400 W kg⁻¹, highlighting its high P_d with minimal energy loss. The CoS₂@C//RGO device maintained 81.12% capacitance retention as well as 91.7% Coulombic efficiency over 10 000 cycles at 10 A g⁻¹ (Fig. 17(n)).²⁷¹ Zhao et al. used a self-sacrificing template strategy to construct uniform carbon-modified NiS/NiS₂ yolk–shell spheres from a Ni-based metal organic framework (Ni-MOF) precursor. The NiS/NiS₂@C nanocomposites demonstrate a high specific capacity of 1082 C g⁻¹ at 1 A g⁻¹ and maintain excellent cycling stability with 85% capacity retention after 5000 cycles. Additionally, a hybrid supercapacitor using this nanocomposite and porous carbon can achieve a high E_d of 56.2 Wh kg⁻¹ at 800 W kg⁻¹ and retain 86% capacity after 10 000 charge/discharge cycles, as shown in Fig. 18(a–d). The authors state that the improved electrochemical performance results from the yolk–shell structure, which provides internal voids to accommodate volume changes while preserving integrity. The carbon coating enhances conductivity, facilitates electron flow, and strengthens stability. Additionally, the combination of NiS and NiS₂ phases enhances redox activity, thereby improving charge storage.²⁷⁶

Fig. 18 (a) Electrochemical performance of NiS/NiS₂@C and NiS_x: CV curves at 20 mV s⁻¹, (b) GCD curves at 1 A g⁻¹, (c) capacity at various current densities, and (d) cycling stability. (e) Schematic of the NiS/NiS₂@C//PAC device, (f) cycling stability and coulombic efficiency, (g) Ragone plots, and (h) LED lighting images powered by two HSCs. Reproduced from ref. 276 with permission from Springer Nature, copyright 2025.

Han et al. incorporated MoSe₂ nanosheets into carbon aerogel microspheres (MoSe₂ NSs/CRF) via a solvent-thermal method, enhancing both specific surface area as well as electrical conductivity. The MoSe₂ NSs/CRF electrode achieved a C_s of 498 F g⁻¹ at 1 A g⁻¹, three times higher than that of pristine MoSe₂ (136 F g⁻¹). At 5 A g⁻¹, it retained 278 F g⁻¹ with 127.2% capacitance retention at 100 mV s⁻¹ over 2500 cycles. The symmetric SC fabricated with the composite showed a capacitance of 124 F g⁻¹, an E_d of 8.5 Wh kg⁻¹, and a P_d of 264.8 W kg⁻¹ at 1 A g⁻¹.²⁷⁷ Furthermore, Tanwar et al. synthesised the MoSe₂@AC composite using a simple hydrothermal method and methods employed for the preparation of the electrodes and the six-day-aged M6AC exhibited superior electrochemical performance. The symmetric cell fabricated with M6AC achieved a C_s of 394 F g⁻¹ at 1 A g⁻¹ in 6 M KOH electrolyte as shown in Fig. 19(a). It delivered an E_d of 55 Wh g⁻¹ and a P_d of 845 W kg⁻¹ at 1 A g⁻¹ (Fig. 19(b)). The M6AC-based devices demonstrated 85% cycling stability and 100% coulombic efficiency following 3000 cycles, as presented in Fig. 19(c). Fig. 19(d) shows the GCD profiles recorded before and after 3000 cycles of the stability test at 2 A g⁻¹. Fig. 19(e) shows the charge storage mechanism before and after charging. To test practical usability, the M6AC symmetric cell powered 26 red LEDs connected in parallel for approximately 32 minutes as shown in Fig. 19(f).²⁷⁸ Li et al. grew ultrathin MoSe₂ nanosheets (MoSe₂ NSs) on multi-walled carbon nanotubes (MWCNTs) via a hydrothermal method. The MoSe₂/MWCNT composite exhibited a maximum C_s of 927.25 F g⁻¹ and retained 70.08% of its initial capacity after 3000 cycles at 1 A g⁻¹. An asymmetric SC using MoSe₂/MWCNT as the anode and activated carbon (AC) as the cathode showed a C_s of 233.3 mF cm⁻² at 1 mA cm⁻², 101 mF cm⁻² at 10 mA cm⁻², and a specific energy of 72.9 µWh cm⁻² at 849.3 mW cm⁻², with 67.4% capacitance retention after 3000 cycles. At 10 mA cm⁻², it achieved a P_d of 5980 mW cm⁻².²⁷⁹ Gao et al. synthesised CNT@NiCo-Se using Ni-Co PBA with an etching and isolation technique, resulting in CNTs with smaller diameters and larger interlayer spacing. This structure enhanced charge transfer and –OH binding energy, leading to superior SC performance. The electrode achieved a specific capacity of 105.1 mAh g⁻¹ at 1 A g⁻¹, and the ASC device delivered an E_d of 46.3 Wh kg⁻¹ at 801 W kg⁻¹ with 80.4% capacitance retention after 10 000 cycles. This approach provides a novel way to optimise CNT-based materials for energy storage.²⁸⁰

Fig. 19 (a) GCD curves at several current densities, (b) Ragone plot comparing the performance, with the inset showing the variation of C_s with current density, (c) capacitance retention and coulombic efficiency over an increasing number of cycles, with the inset highlighting the GCD curves of the final 25 cycles, (d) GCD profiles recorded before and after 3000 stability cycles under constant conditions of 100 mV s⁻¹ and 2 A g⁻¹ respectively, (e) proposed charge storage mechanism during: (a) the charging process and; (b) the discharging process, and (f) practical demonstration of the M6AC-based SC powering multiple LEDs, including various colors and a display panel of 26 red LEDs. Reproduced from ref. 278 with permission from Elsevier, copyright 2023. (g) Plot illustrating C_s as a function of current density for all the composite materials, (h) EIS profile of all materials, (i) stability cycle of the MoTe₂/rGO nanocomposite, and (j) CV cycling stability. Reproduced from ref. 146 with permission from Elsevier, copyright 2023.

Li et al. reported that 1T′-MoTe₂ nanoparticles on reduced graphene oxide (1T′-MoTe₂ NPs/rGO), synthesised via in situ tellurization of MoO₂, exhibit excellent electrochemical performance. The 1T′-MoTe₂ NPs/rGO SC achieves 98.8 F g⁻¹ at 1 A g⁻¹, excellent rate capacitance, and high stability, owing to enhanced conductivity and increased surface area.²⁸¹ Sarwar et al. used microwave-initiated synthesis of MoTe₂/graphene nanosheets to yield a high-performance energy storage material. It shows a C_s of 434 ± 37.5 F g⁻¹ at 1 A g⁻¹, 125% retention after 5000 cycles, and excellent stability up to 10 000 cycles in 1 M Na₂SO₄. The symmetric device achieves an E_d of 43.2 Wh kg⁻¹ at 3000 W kg⁻¹.²⁸² Furthermore, as shown in Fig. 19(g–j), Abdullah et al. showed that the MoTe₂/rGO nanocomposite, synthesised via a cost-effective hydrothermal method, exhibits exceptional SC performance in a 2 M KOH electrolyte. It achieves a C_s of 1196 F g⁻¹ (GCD) and 757.40 F g⁻¹ (CV), a specific energy of 83.06 Wh kg⁻¹, and a specific power of 353.5 W kg⁻¹. With 94.23% capacitance retention after 5000 cycles, its superior performance is attributed to the synergy between MoTe₂ and rGO nanosheets. This simple, scalable material is highly promising for green energy SCs.¹⁴⁶ Zhang et al. presented a strategy using MOF-derived carbon materials to enhance Co-based nanoparticle anodes. By sequential carbonisation, oxidation, and tellurization of ZIF-67, CoTe₂@N-C composites were developed, demonstrating superior Li⁺ storage, high-rate capacity, and excellent cycling stability. The resulting lithium-ion capacitor achieved a high E_d of 144.5 Wh kg⁻¹ and a P_d of 10 kW kg⁻¹, and retained 90.95% capacity after 1000 cycles. The carbon coating effectively stabilised the structure, preventing collapse and active material loss, showcasing the potential of MOF-derived materials for high-performance ESDs.²⁸³

5.2.2 Conductive polymer/TMDs. Conductive polymers such as polypyrrole (PPy), polyaniline (PANI), polythiophene (PTh), and poly(3,4-ethylenedioxythiophene) (PEDOT) exhibit high conductivity, capacitance, and flexibility, and are environmentally friendly, which renders them suitable for SC applications.²⁸⁴ When combined with 2D TMDs, these polymers facilitate shorter ion/electron diffusion pathways. The presence of 2D TMDs enhances the cycle life of polymer-based electrodes and improves mechanical stability. Such hybrid structures are typically fabricated through in situ polymerisation. Chen et al. prepared a similar urchin-like MoS₂@PANI; electrostatic and hydrogen bond interactions between MoS₂ and PANI enhance the structural integrity and surface area of the hybrids. MoS₂@PANI (25 wt% MoS₂) achieved a C_s pf 645 F g⁻¹ @ 0.5 A g⁻¹, also 89% retention after 2000 cycles. Compared to pure PANI (335 F g⁻¹), these hybrids show improved energy storage, making them promising materials for hybrid SCs.²⁸⁵ Moghaddam et al. explored group 6 TMDs (MX₂; M = Mo, W; X = S, Se, Te) as advanced electrode materials for SCs. MoTe₂ nanosheets demonstrate good gravimetric C_s (45 F g⁻¹ @ 0.4 A g⁻¹), followed by WS₂ (32 F g⁻¹) & MoS₂ (25 F g⁻¹). Combining MX₂ with polyaniline (PANI) significantly enhanced capacitance. The MoTe₂/PANI composite exhibited the best performance with 499 F g⁻¹, a 76% improvement over that of pure PANI (283 F g⁻¹). This enhancement is due to the increased active surface area, making MX₂/PANI hybrids promising for energy storage applications.²⁸⁶

5.2.3 Metal oxide (/hydroxides)/TMDs. TMD and TMO composites synergistically combine the excellent conductivity and flexibility of TMDs with the high capacitance of TMOs, leading to significantly enhanced electrochemical performance.²⁸⁷ Nabi et al. reported that the NiMoO₄/TiS₂ (NT-1) composite, prepared via hydrothermal synthesis, shows excellent SC performance with a high C_s of 1257.14 F g⁻¹ at 1 A g⁻¹ and 92% retention after 5000 cycles. Its mesoporous structure, large surface area, and efficient charge transfer contribute to enhanced durability, making it highly effective for advanced SC applications.²⁸⁸ Choudhary et al. developed h-WO₃/WS₂ core/shell nanowires for SCs, combining 1D nanowires and 2D TMD layers with robust interfaces. The design achieved excellent performance, including long-term stability over 30 000 cycles and high capacitance.¹⁸¹ Gao et al. prepared CoSe₂@NiCo-LDH composite electrodes with high conductivity and abundant redox sites. They achieved 6.06 F cm⁻² at 6 mA cm⁻² and excellent ion adsorption in KOH. Asymmetric SCs showed 0.183 mWh cm⁻² E_d, 40 mW cm⁻² P_d, and 97.82% capacitance retention over 5000 cycles, demonstrating high stability and performance.²⁸⁹

5.2.4 MXene/TMDs. In recent years, 2D transition metal carbides and nitrides (MXenes), such as Ti₃C₂T_x, have gained popularity as electrode materials for SCs owing to their lamellar structure, high electrical conductivity, and active sites. However, their limited C_s presents a challenge. To address this, MXenes are often decorated with pseudocapacitive materials. The synthesis of MXenes involves etching and exfoliation of MAX phases (for example, Ti₃AlC₂) in strong etchant solutions. Surface functionalization is employed to improve compatibility and dispersion. MXene composites are subsequently fabricated using methods such as solution mixing, hydrothermal synthesis, chemical vapor deposition (CVD), or physical vapor deposition (PVD), to enhance performance tailored to specific applications.^290–292 Raj KA et al. developed VSe₂/MXene hybrid materials for enhanced SC performance. The VSe₂/MXene heterostructure achieved a C_s of 144 F g⁻¹ @ 1 A g⁻¹, along with 92.8% retention after 5000 cycles. DFT simulations revealed improved electronic properties, enhanced states near the Fermi level, and lower diffusion barriers due to charge transfer from Ti 3d orbitals of MXenes to V 3d orbitals of VSe₂. An asymmetric SC with VSe₂/MXene//MoS₂/MWCNT electrodes delivered an E_d of 42 Wh kg⁻¹ at 2316 W kg⁻¹, retaining 90% C up to 5000 cycles.²⁹³ Furthermore, Xiao et al. presented a solvothermal method to produce CoSe₂@Ti₃C₂T_x heterostructures by confining CoSe₂ within MXene-Ti₃C₂T_x layers. The Schottky heterostructures enhance Na⁺ ion adsorption, fast ion transport, and cycling stability. As an anode, it achieves 600.1 mAh g⁻¹ capacity, excellent rate performance, and long durability. The sodium-ion capacitor with CoSe₂@Ti₃C₂T_x and activated carbon shows high energy (125 Wh kg⁻¹) and P_d (22.5 kW kg⁻¹) with 86.3% retention over 15 300 cycles.²⁹⁴

5.2.5 TMDs/TMDs. Another composite synthesised by Gul et al., i.e. the ZrS:BaS:Ni₉S₈ thin film via a resistive heating method, shows a 21 nm crystallite size and a 2.5 eV optical band gap. It achieved a C_s of 540.7 F g⁻¹ with excellent cycling stability, making it a promising material for high-performance SC applications.²⁹⁵ Wang et al. prepared MoS₂/CoS₂ NSTAs, and these arrays, grown directly on Ti plates, enhance electrical conductivity and simplify electrode preparation. The MoS₂/CoS₂ NSTAs demonstrated a C_s of 142.5 mF cm⁻² @ 1 mA cm⁻², almost twice that of MoS₂ nanosheets and 50 times that of CoS₂ arrays. They also exhibited outstanding long-term reliability, with 92.7% retention up to 1000 cycles. Synergistic effects from MoS₂ and CoS₂ make MoS₂/CoS₂ NSTAs promising electrode materials for SCs.²⁹⁶ Also, the MoS₂@CoS₂ material was prepared by Iqbal et al. through the one-step hydrothermal method, combining flower-like MoS₂ and square-shaped CoS₂ for enhanced SC performance. It achieves a C_s of 199 F g⁻¹ @ 2 A g⁻¹, E_d of 27.74 Wh kg⁻¹, and P_d of 494.46 W kg⁻¹. Their unique structure prevents MoS₂ restacking, improves ion dynamics, and enhances conductivity. Additionally, it powered an LED for over 3 minutes, demonstrating its practical potential.²⁹⁷

Patel et al. presented a MoSe₂@WSe₂ nanohybrid heterostructure (HS) electrocatalyst, synthesised via liquid-phase exfoliation of nanocrystals. Better electrocatalytic performance led to increased availability of active edge spots following exfoliation, along with the synergistic interactions at the heterostructure interfaces between MoSe₂ and WSe₂. FSSC, depending upon an HS catalyst, showed admirable electrochemical performance, with a C_s of 401 F g⁻¹ @ 1 A g⁻¹ and 97.20% retained up to 5000 cycles, with good flexibility, and stability maintained after 1000 bend cycles.²⁹⁸ MoSe₁₈Se₂₄ and Mg₃Mo₁₈Se₂₄ (MoSe/MMSe) composite electrodes were synthesised by Nagaraju et al. on Ni foam (NF) via hydrothermal synthesis. The MoSe/MMSe composite showed superior areal capacity (1154.4 µAh cm⁻²) and specific capacity (250.9 mAh g⁻¹) compared to individual electrodes. The electrochemical properties of MoSe and MgSe were also analysed. An OAC/NF (OAC onion-derived activated carbon) negative electrode was used, showing high capacitance. The MoSe/MMSe/NF (positive)//OAC/NF (negative) hybrid SC delivered an E_d of 28.5 Wh kg⁻¹ and P_d of 2353.8 W kg⁻¹, with 74.3% retained after 45 000 cycles.²⁹⁹

Shamami et al. introduced CoTe@CoFeTe double-shelled nanocubes as advanced SC materials, synthesised through anion exchange, annealing, and tellurization processes. The unique porous structure and incorporation of tellurium enhance conductivity, ion diffusion, and electron transport. These nanocubes achieve an extraordinary specific capacity of 1312 C g⁻¹ at 1 A g⁻¹ and retain 92.35% capacity after 10 000 cycles. A HSC (AC//CoTe@CoFeTe) exhibits high E_d (64.66 Wh kg⁻¹) and excellent cycling stability (88.25% retained up to 10 000 cycling).³⁰⁰ Liu et al. synthesised NiSe/NiTe₂ nanocomposites via a microwave method on nickel foam, demonstrating exceptional performance for SCs. It achieved a C_s of 1782.7 F g⁻¹ @ 1 A g⁻¹, surpassing individual NiSe and NiTe₂ electrodes. The composite shows excellent cycling stability, and retained 81.5% up to 30 000 cycles. Additionally, the NiSe/NiTe₂//AC ASC delivered an E_d of 23.26 Wh kg⁻¹ and retained 84.8% after 20 000 cycles. The data emphasise the viability of the NiSe/NiTe₂ composite for high-performance and durable SCs.³⁰¹

5.2.6 Mixed composites. Mixed composites, involving the integration of TMDs with other materials such as metal oxides, carbon-based materials (like graphene and CNTs), or conductive polymers, aim to harness the optimal properties of each constituent. This approach is particularly pertinent to SC applications, as it markedly improves overall capacitance, electrical conductivity, and cycle stability. For example, Vinodhini et al. designed a mixed electrode by combining TiO₂ and CNTs (i.e. MoS₂/TiO₂/CNTs) that outperformed and achieved 1252.57 mAh g⁻¹ at 20 mV s⁻¹ in 1 M KOH, with significantly lower impedance (R_ct 1.7 Ω cm², R_f 2.1 Ω cm²). It demonstrated excellent cycling stability, retaining 98.83% capacitance after 10 000 cycles @ 1 A g⁻¹. The E_d was 757.80 Wh kg⁻¹, and the P_d was 4546.80 W kg⁻¹.³⁰² Siddu et al. prepared a 3D hybrid structure of VSe₂, Ti₃C₂T_x MXene, and CNTs to overcome challenges like oxidation and sheet restacking in SCs. The VSe₂/e-MXene/CNT_30 electrode exhibits excellent electrochemical performance, with high capacitance and improved rate capability. It shows the largest CV area, indicating superior activity, delivers a higher C_s of 151 F g⁻¹ @ 1 mA, and maintains 98.1% capacitance retention and nearly 100% CE up to 5000 cycles. An ASC with this hybrid achieved 35.91 Wh kg⁻¹ E_d, 1280 W kg⁻¹ P_d, and retained 24.17 Wh kg⁻¹ at 6350 W kg⁻¹, demonstrating strong rate capability. The device maintained ∼99% capacitance retention and nearly 100% coulombic efficiency after 5000 cycles, confirming its stability and efficiency.³⁰³ Gao et al. developed CNTs with NiSe₂/CoSe₂ nanoparticles (CNT@NiCo-Se) using an etching and isolation technique, achieving smaller tube diameters and larger interlayer spacing. These enhancements improve charge transfer and binding energy, resulting in a 375% higher specific capacity (105.1 mAh g⁻¹ at 1 A g⁻¹). The CNT@NiCo-Se//AC SC delivers 46.3 Wh kg⁻¹ E_d and 8000 W kg⁻¹ P_d, and retains 80.4% capacitance after 10 000 cycles, showcasing a new method for optimising PBA-derived materials.²⁸⁰

In the meantime, Su et al. synthesised a Ni₂P/NiSe₂/MoSe₂ (NNM) hybrid to address MoSe₂ restacking issues in SCs. Embedding Ni₂P and NiSe₂ nanoparticles within MoSe₂ nanosheets increased interlayer spacing, enhanced active sites, and improved electron transfer. The NNM electrode achieved a C_s 607.5 F g⁻¹ @ 0.5 A g⁻¹, and also retention of 87.9% up to 1000 cycles. An NNM//AC hybrid SC delivered 23.5 Wh kg⁻¹ @ 400 W kg⁻¹ with exceptional durability, retaining 116.6% up to 45 000 cycles, showcasing feasibility for advanced energy storage.³⁰⁴ Farshadnia et al. studied a NiTe₂-Co₂Te₂@rGO nanocomposite successfully using a two-step hydrothermal method, and the electrochemical tests demonstrate excellent performance, with a specific capacity of 223.6 mAh g⁻¹ at 1 A g⁻¹ and 89.3% stability after 3000 cycles. The hybrid SC, with NiTe₂-Co₂Te₂@rGO as the cathode, and activated carbon as the anode, gave an E_d of 51 Wh kg⁻¹ and P_d of 800 W kg⁻¹. This electrode also powers LEDs for 20 minutes, validating its performance for future next-generation storage platforms in devices and vehicles.¹¹

5.2.7 Others. Qadeer et al. produced a Bi₂WO₆/TiS₂ (BW/T@40%) composite by the hydrothermal process, achieving a high C_s of 1153.3 F g⁻¹ because of increased surface area, pore size, and also synergistic effects. It also demonstrated excellent stability, retaining 92% capacitance after 4500 cycles.³⁰⁵ The overall conclusion of the recent study indicates that the integration of TMDs with various materials through compositing serves not only to enhance their inherently low electrical conductivity and limited surface area but also as a strategic approach to regulate charge transfer, redox reactions (electron exchange), and voltage stability. Notably, when TMDs such as VSe₂ are combined with MXenes, orbital interactions occur between them, resulting in increased electron flow and equilibrium in redox processes. Structural design is equally crucial; for instance, vertically aligned, porous hollow materials facilitate ion mobility, prevent material degradation, and provide abundant active sites. An additional consideration pertains to aqueous systems, where the voltage window is typically constrained due to the rapid onset of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, this limitation can be mitigated by controlling the edge sites of the material, selecting appropriate electrolytes, and meticulously designing the interface. The synthesis method employed, whether solvothermal or metal–organic framework (MOF)-based techniques, not only determines the morphology but also influences the phase formation, defect density, and overall stability of the material. In conclusion, the creation of composites is a deliberate and strategic process rather than an arbitrary mixture. This process involves a comprehensive balance of TMD quantity, structural features, and the electrolyte environment to produce an energy storage system that is efficient, evidencing a purposeful electrochemical design rather than a random material combination. The integration of electronic behaviour, structural design, and electrochemical performance establishes a new paradigm for future TMD composites. Moving forward, research should extend beyond merely discovering new materials to focusing on how existing materials can be engineered into intelligent, integrated, and functional systems, wherein each component supports the others. A comparison table indication the supercapacitor performance of all type of TMD-based electrodes have been compared in Table 2.

Table 2 TMD-based electrodes' performance for SCs^a

Electrode materials	Device technique	Cs @ current density/scan rate	Cycles	Capacitance retention	Ed	Pd	Ref.
a PEI@ACWPANI HCFMs: flexible silver-anchored polyetherimide@CNP/WS2/polyaniline coaxial fibrous membranes.
Pristine TMDs
1T-TiS2	Symmetric	—	10 000	96.1%	—	2000 W kg^−1	213
TiS2	Symmetric	68.62 mF cm^−2 @ 0.375 mA cm^−2	5000	4% loss	34.35 mWh cm^−2	675.1 mW cm^−2	306
TiSe2	Asymmetric	60.6 F g^−1 @ 0.2 A g^−1	—	—	38.1 Wh kg^−1	176.4 W kg^−1	307
TaS2	Three electrodes	151.11 F cm^−2 @ 0.3 A g^−1	5000	81%	—	—	308
TaSe2	Three electrodes	102.6 F cm^−2 @ 0.3 A g^−1	5000	98%	—	—	308
WS2	Three electrodes	116.1 F cm^−2 @ 0.3 A g^−1	5000	98%	—	—	308
WSe2	Three electrodes	152.3 F cm^−2 @ 0.3 A g^−1	5000	98%	—	—	308
ZrS2	Three electrodes	141.8 F cm^−2 @ 0.3 A g^−1	5000	92%	—	—	308
ZrSe2	Three electrodes	127.3 F cm^−2 @ 0.3 A g^−1	5000	92%	—	—	308
VS2	Asymmetric	155 F g^−1 @ 1 A g^−1	5000	99%	42 Wh kg^−1	700 W kg^−1	309
2D-pristine VS4	Three electrodes	215 F g^−1 @ 5 mV s^−1	2000	82%	—	—	310
Hierarchical NbS2	Three electrodes	221.4 F g^−1 @ 1 A g^−1	10 000	78.9%	—	—	311
Ultrathin NbS2	Three electrodes	175.6 F g^−1 @ 1 A g^−1	—	—	—	—	311
Mesoporous MoS2	Three electrodes	403 F g^−1 @ 1 mV s^−1	2000	80%	—	—	188
1T-2H WS2	Hybrid	240.7 F g^−1 @ 1 A g^−1	—	95.7%	65.5 Wh kg^−1	784 W kg^−1	312
WSe2 nanoflakes thin-film	Symmetric	88 mF cm^−2	5000	75.36%	27.5 µWh^−1 cm^−2	3000 µW cm^−2	313
CoSe2	Asymmetric	90.5 F g^−1 @ 10 mA cm^−2	—	—	32.2 Wh kg^−1	1914.7 W kg^−1	314
Modified TMDs
TiS2/MoS2	Three electrodes	709 F g^−1 @ 10 mV s^−1	4000	91%	—	—	315
rGO/TiS2/MoO3	Three electrodes	1100 mAh g^−1 @ 1 A g^−1	8000	98.83%	882 Wh kg^−1	5773 W kg^−1	316
3D patterned MoS2/TiS2	Two electrodes	448.16 mF cm^−2 @ 90 mg cm^−2	100 000	99.1%	3.89 µWh cm^−2	250 µW cm^−2	317
PPT/ZrO2/ZrS2	Three electrodes	1326 F g^−1 @ 5 A g^−1	10 000	96%	166 Wh kg^−1	664 W kg^−1	318
VS2/MWCNT	Symmetric	182 F g^−1 @ 2 mV s^−1	5000	93.2%	42 Wh kg^−1	2.8 kW kg^−1	319
NiCo2S4@VS2	Asymmetric	299.5 C g^−1 @ 1 A g^−1	4000	—	31.2 Wh kg^−1	775 W kg^−1	320
2D VS2-black phosphorus-50	Symmetric	203.25 mF cm^−2 @ 1 mA cm^−2	10 000	87%	28.22 µWh cm^−2	596.09 mW cm^−2	321
VSe2/SWCNTs/rGO	Symmetric	450 F g^−1 @ 1 A g^−1	5000	91%	131.4 Wh kg^−1	27.49 kW kg^−1	322
S-VSe2/CNT	Asymmetric	96 mF cm^−2 @ 4 mA cm^−2	5000	87.2%	36.3 µWh cm^−2	3.2 mW cm^−2	323
N doped V4C3/C//VO2/VSe2	Asymmetric	50.6 F g^−1 @ 0.25 A g^−1	5000	78%	21.4 Wh kg^−1	4.5 kW kg^−1	324
VSe2/MWCNT	Symmetric	233.33 F g^−1 @ 2 A g^−1	5000	87%	46.66 Wh kg^−1	4.8 kW kg^−1	325
VSe2/RGO	Coin cell	680 F g^−1 @ 1 A g^−1	10 000	81%	212 Wh kg^−1	3.3 kW kg^−1	326
VSe2@N-doping carbon	Asymmetric	313.8 F g^−1 @ 1 A g^−1	2000	90%	85.41 Wh kg^−1	701.99 W kg^−1	327
3D VSe2/e-MXene/CNT	Asymmetric	101 F g^−1 @ 1.6 A g^−1	5000	99%	35.91 Wh kg^−1	1280 W kg^−1	303
3D VTe2/MXene/CNT	Symmetric	34.2 mF cm^−2 @ 0.25 mA cm^−2	10 000	78%	6.84 µWh cm^−2	304.7 µW cm^−2	328
NiCu-MOF/NbS2	Asymmetric	194 C g^−1 @ 1 A g^−1	20 000	97%	83 Wh kg^−1	970 W kg^−1	329
NbSe2@PPy	Asymmetric	401 mF cm^−2 @ 0.5 mA cm^−2	10 000	98.2%	11.9 mWh cm^−3	29.6 mW cm^−3	330
NbTe2@rGO	Symmetric	498 F g^−1 @ 1 A g^−1	—	—	22 Wh kg^−1	285 W kg^−1	331
PEDOT:PSS/WS2	Three electrodes	118 mF cm^−2 @ 0.5 mA cm^−2	5000	95.7%	14.75 µWh cm^−2	249.31 µW cm^−2	332
Ni@Cu/WS2	Asymmetric	265.42 F g^−1 @ 0.5 A g^−1	4500	98.1%	43.9 Wh kg^−1	425 W kg^−1	333
1T-WS2/Gr	Three electrodes	2964 mF cm^−2 @ 4 mA cm^−2	1000	86%	—	—	334
WS2/carbon composite (WS2/Z8-800)	Asymmetric	88 F g^−1 @ 1 A g^−1	3000	78.3%	25 Wh kg^−1	801 W kg^−1	335
W2C/WS2	Symmetric	328 F g^−1 @ 1 A g^−1	—	—	45.5 Wh kg^−1	0.5 kW kg^−1	336
WS2-WO3/rGO	Three electrodes	728 F g^−1 @ 1.25 A g^−1	3000	91%	—	—	337
WS2/FeCoTeZr	Asymmetric	150 F g^−1 @ 1 A g^−1	3000	97.9%	55 Wh kg^−1	4250 W kg^−1	338
MXene/WS2	Three electrodes	373 F g^−1 @ 0.4 A g^−1	1000	91.2%	—	—	339
h-BN-WS2	Asymmetric	142.1 C g^−1 @ 1 A g^−1	10 000	81.6%	33.37 Wh kg^−1	844.9 W kg^−1	340
PEI@ACWPANI HCFMs	Symmetric	1381.2 mF cm^−2 @ 0.5 mA cm^−2	10 000	76.3%	122.78 µWh cm^−2	0.24 mW cm^−2	341
MnSe/WSe2	Three electrodes	1326 F g^−1 @ 1 A g^−1	5000	92%	37 Wh kg^−1	225 W kg^−1	342
MXene/WSe2	Symmetric	246 F g^−1 @ 2 A g^−1	5000	97%	12.3 Wh kg^−1	600 W kg^−1	343
2H-WSe2@rGO	Asymmetric	145 F g^−1 @ 2 A g^−1	3000	82%	51.5 Wh kg^−1	2133.3 W kg^−1	344
1T-WSe2/graphene	Symmetric	323.3 F g^−1 @ 0.5 A g^−1	5000	86.7%	48.2 Wh kg^−1	250 W kg^−1	345
WSe2@rGO	Three electrodes	1337 F g^−1 @ 1 A g^−1	5000	—	53 Wh kg^−1	261 W kg^−1	346
MoSe2@WSe2	Symmetric	401 F g^−1 @ 1 A g^−1	5000	97.2%	14.44 Wh kg^−1	397 W kg^−1	298
WSe2/MoS2	Three electrodes	1169.53 F g^−1 @ 1 A g^−1	5000	82.80%	161.8 Wh kg^−1	950.2 W kg^−1	347
WSe2@ReSnSe2	Symmetric	175 F g^−1 @ 1 A g^−1	5000	84.6%	3.88 Wh kg^−1	411 W kg^−1	348
WSe2/NiCo-MOF nanocomposites	Asymmetric	270.5 C g^−1 @ 1.5 A g^−1	5000	86.7%	38.8 Wh kg^−1	1791.4 W kg^−1	349
CoS2/MWCNT	Three electrodes	1486 F g^−1 @ 1 A g^−1	10 000	80%	—	—	350

---

6. Conclusion and future perspectives

6.1 Conclusion

Energy is essential for human needs and development. The search for renewable energy sources has intensified, with SCs gaining attention as a promising solution for the depletion of fossil fuels. SCs offer high P_d, fast charge/discharge rates, and longer lifespans than batteries and fuel cells, making them suitable for electric vehicles, hybrid systems, and emergency power applications. An SC cell has two electrodes and an electrolyte; the electrode is vital for storing charge and determining performance. Ideal electrode features include high surface area, conductivity, porosity, low cost, and stability. In the last few decades, TMDs have been promising electrode materials for SC applications. Hence, in this review article, we present an in-depth analysis of the structure and properties of TMDs, along with an exploration of various synthesis routes for TMD-based materials. Thereafter, the supercapacitive behaviour of TMDs in energy storage applications has also been thoroughly discussed, with emphasis on the critical roles of defects, morphology, surface area, doping, pore size, and compositional variations in optimising their performance. TMDs exhibit attractive features like a broad exposed area, adjustable band gap, and enhanced physical robustness, thus allowing them to serve as ideal candidates for layered geometries. Nevertheless, their weak electron transport efficiency restricts their effectiveness in energy conservation, prompting the development of several strategies to enhance their conductivity. The key strategies highlighted in this review to tackle this challenge are mixing, wrapping, or depositing TMDs with a range of organic/inorganic capacitive materials. However, some challenges remain that need to be addressed to meet the current energy demand.

6.2 Future perspectives

Although optimized 2D TMD-based SCs show great potential, acknowledging current problems and challenges is important. Addressing these issues should guide future research. We emphasize the following points, as illustrated in Fig. 20 and discussed in detail below:

Fig. 20 Exploring challenges and emerging trends in TMDs for SCs.

6.2.1 Surface functionalization. Surface functionalization addresses the inherent drawbacks of TMD-based SC electrodes, including restacking, slow ion diffusion, and limited conductivity. Adding heteroatoms (N, O, snf S), functional groups, and conducting polymers to their surface increases the electroactive sites and enhances charge transfer. Also, controlled functionalisation methods, such as atomic-level doping, defect engineering, and hybridisation with carbon frameworks, can enhance structural stability and minimise volume changes during long-term cycling. Furthermore, incorporating redox-active groups and metal oxides onto the TMD surface provides additional pseudocapacitance without affecting conductivity. In addition, the heterojunction design that combines different 2D TMD materials, such as MoS₂, WS₂, and TiS₂, generates built-in electric fields. This enhances charge storage and transfer capabilities and helps prevent electrode collapse. With surface doping, ion and electron migration improve, and the kinetics of the electrochemical reaction are optimised. By making protective films, oxidation resistance and chemical stability improve. The biggest challenge is ensuring that the functionalization is scalable, uniform, and durable, enabling practical device fabrication. If these hurdles can be overcome, then TMD-based electrodes for SCs offer high E_d, fast charge and discharge, and, along with excellent durability, can provide a strong foundation for next-generation SCs.

6.2.2 Morphological engineering and nanoscale confinement. Future research on TMD-based electrodes for SCs should strongly focus on advanced morphological engineering combined with nanoscale confinement strategies to unlock their full electrochemical potential, enabling high E_d, P_d, and long-term cycling stability. Designing advanced nanoscale structures, including nanosheets, nanotubes, nanorods, and hierarchical networks with controlled porosity, can greatly increase surface area and reduce ion diffusion paths, thereby improving charge storage and transfer kinetics. Additionally, accurately controlling ultrathin or few-layer structures can leverage quantum confinement effects, boosting electrical conductivity and redox activity. Also, in the future, modulating interlayer spacing and using conductive nanomaterials and molecular spacers can optimise ion accessibility and mitigate volumetric expansion during repeated cycles. Apart from these, multi-scale morphological design, which combines nanoscale engineering with meso and macroscale architectures, will be crucial for simultaneously achieving high E_d and P_d. The synergistic optimisation of porosity, layer alignment, and surface functionalisation will unlock superior cycling stability and long-term durability.

6.2.3 AI and machine learning assisted material calculations. In the future, the design and development of 2D TMDs are anticipated to progress more rapidly through the integration of Artificial Intelligence (AI) and Machine Learning (ML). The existing experimental and computational databases can aid AI–ML algorithms in predicting and optimising synthesis parameters, processing conditions, and defect engineering. AI–ML models can help identify enhanced specific design factors for TMD electrode materials, such as mass ratios, charge–discharge modes, potential ranges, and fabrication methodologies. The integration of AI–ML has not only facilitated material synthesis but has also conserved resources and time. Furthermore, AI–ML is highly valuable for analysing electrochemical behaviour, enabling the prediction of SC performance.

6.2.4 DFT and multiscale simulations. In the near future, DFT and multiscale simulations will become the cornerstone tools for the rational design of TMD-based SC electrodes. With the help of DFT, the atomic-level electronic structure, orbital hybridisation, defect states, edge vs. basal-plane activity, and ion-intercalation energetics can be predicted with high fidelity. This allows the redox site activation, charge redistribution, local strain effects and conductivity pathways to be engineered on the atomic scale. In particular, the effects of vacancy defects, heteroatom doping, and functional group modifications on electrochemical potential, Fermi-level tuning, and adsorption energies are quantified accurately, which influence the electrode's performance. Multiscale simulations (molecular dynamics, reactive force fields, coarse-grained modelling, kinetic Monte Carlo, and continuum electrochemical simulations) can couple atomic-scale phenomena with mesoscale morphology and device-level electrochemical behaviour, enabling the prediction of ion transport kinetics, electrolyte penetration, and electrode porosity optimisation.

6.2.5 Advanced in situ characterisation. In future studies, the advanced in situ characterisation techniques have facilitated a comprehensive understanding of reaction mechanisms, material behaviours, and hidden phenomena under realistic conditions.³⁵¹ Techniques such as in situ Raman spectroscopy, infrared (IR) spectroscopy, in situ transmission electron microscopy (TEM), in situ scanning electron microscopy (SEM), in situ X-ray diffraction (XRD), in situ X-ray absorption spectroscopy (XAS), and in situ X-photoelectron spectroscopy (XPS) enable real-time observation of structural, compositional, and electronic changes during reactions.³⁵² These methods are instrumental in directly tracking material transformations in both equilibrium and non-equilibrium states.³⁵³ They contribute to improving interfacial phenomena, enhancing battery stability, and supporting practical applications. Such tools are vital for understanding the intrinsic properties of 2D TMDs and their dynamic alterations, which are crucial for the development of energy-related technologies.

6.2.6 Techno-economic optimization of TMD-based SCs. TMDs provide high C_s and E_d but face commercialization challenges due to low conductivity, restacking, and high synthesis costs. From a techno-economic perspective, the synthesis routes discussed in this review are largely compatible with scalable processes such as hydrothermal, solution-phase, and gas-phase methods, although further optimization is required to reduce processing complexity and energy consumption. Economically, the cost of raw materials, use of costly precursors, and multi-step fabrication procedures remain key cost drivers that may hinder large-scale commercialization. Therefore, future efforts should focus on low-cost precursors, simplified synthesis strategies, and improved material utilization to enhance cost-effectiveness. Overall, while the reviewed materials demonstrate promising performance at the laboratory scale, targeted techno-economic optimization will be essential to translate these advances into commercially viable energy storage devices, thereby strengthening their application prospects.

Conflicts of interest

There are no conflicts to declare.

Data availability

This manuscript is a review article and does not report any new primary data. All information discussed in this review has been obtained from previously published literature, which has been appropriately cited within the manuscript.

Acknowledgements

Meenakshi gratefully acknowledges the Ministry of Education, India, for financial assistance. P. W. M. gratefully acknowledges funding from the German Federal Ministry of Education and Research under the funding code 03EW0015A/B.

References

1. B. Williams, D. Bishop, P. Gallardo and J. G. Chase, Energies, 2023, 16, 5155.
2. M. Farghali, A. I. Osman, I. M. A. Mohamed, Z. Chen, L. Chen, I. Ihara, P.-S. Yap and D. W. Rooney, Environ. Chem. Lett., 2023, 21, 2003–2039.
3. J. Cherusseri, D. Pandey and J. Thomas, Batteries Supercaps, 2020, 3, 860–875.
4. Y. Shao, M. F. El-Kady, J. Sun, Y. Li, Q. Zhang, M. Zhu, H. Wang, B. Dunn and R. B. Kaner, Chem. Rev., 2018, 118, 9233–9280.
5. C. Zhang, Y.-L. Wei, P.-F. Cao and M.-C. Lin, Renewable Sustainable Energy Rev., 2018, 82, 3091–3106.
6. K. Mensah-Darkwa, C. Zequine, P. K. Kahol and R. K. Gupta, Sustainability, 2019, 11, 414.
7. H. Gupta, M. Kumar, D. Sarkar and P. W. Menezes, Energy Adv., 2023, 2, 1263–1293.
8. T. Ramachandran, R. K. Raji and M. Rezeq, J. Mater. Chem. A, 2025, 13, 12855–12890.
9. J. Cherusseri, N. Choudhary, K. Sambath Kumar, Y. Jung and J. Thomas, Nanoscale Horiz., 2019, 4, 840–858.
10. C. Li, M. M. Islam, J. Moore, J. Sleppy, C. Morrison, K. Konstantinov, S. X. Dou, C. Renduchintala and J. Thomas, Nat. Commun., 2016, 7, 13319.
11. M. Farshadnia, A. A. Ensafi, K. Z. Mousaabadi, B. Rezaei and M. Demir, Sci. Rep., 2023, 13, 1364.
12. N. I. Jalal, R. I. Ibrahim and M. K. Oudah, J. Phys., Conf. Ser., 2021, 1973, 012015.
13. N. Choudhary, C. Li, J. Moore, N. Nagaiah, L. Zhai, Y. Jung and J. Thomas, Adv. Mater., 2017, 29, 1605336.
14. A. González, E. Goikolea, J. A. Barrena and R. Mysyk, Renewable Sustainable Energy Rev., 2016, 58, 1189–1206.
15. S. P. Gupta, P. P. Sanap, M. K. Deore, J. L. Gunjakar, B. R. Sankapal, C. D. Lokhande, Z. Said, A. B. Bhalerao, R. N. Bulakhe and J. M. Kim, J. Energy Storage, 2023, 73, 109065.
16. K.-J. Huang, J.-Z. Zhang and Y. Fan, Mater. Lett., 2015, 152, 244–247.
17. G. Pandey, S. Serawat and K. Awasthi, ACS Nanosci. Au, 2024, 4, 399–408.
18. M. Ojha and M. Deepa, Chem. Eng. J., 2019, 368, 772–783.
19. M. Zhi, C. Xiang, J. Li, M. Li and N. Wu, Nanoscale, 2013, 5, 72–88.
20. Y. Wang, L. Zhang, H. Hou, W. Xu, G. Duan, S. He, K. Liu and S. Jiang, J. Mater. Sci., 2021, 56, 173–200.
21. T. Ramachandran, R. M. N. Kalla, R. Khan, A. G. Al-Sehemi, Y. A. Kumar, A. K. Yadav and J. Lee, J. Power Sources, 2026, 664, 238945.
22. J. Gamby, P. Taberna, P. Simon, J. Fauvarque and M. Chesneau, J. Power Sources, 2001, 101, 109–116.
23. W. Gu and G. Yushin, WIREs Energy Environ., 2014, 3, 424–473.
24. C. Liu, Z. Yu, D. Neff, A. Zhamu and B. Z. Jang, Nano Lett., 2010, 10, 4863–4868.
25. Y. Wang, Z. Shi, Y. Huang, Y. Ma, C. Wang, M. Chen and Y. Chen, J. Phys. Chem. C, 2009, 113, 13103–13107.
26. T. Ramachandran, R. M. N. Kalla, A. G. Al-Sehemi, Y. A. Kumar, R. Khan, A. Ghosh, S. S. Rao and J. Lee, Colloids Surf., A, 2025, 726, 137844.
27. R. Khan, R. M. N. Kalla, T. Ramachandran, A. G. Al-Sehemi, Y. A. Kumar, P. Somu and J. Lee, J. Alloys Compd., 2025, 1039, 182874.
28. T. Ramachandran, R. M. Naidu Kalla, Y. A. Kumar, A. Ghosh, A. G. Al-Sehemi, R. Khan and J. Lee, J. Alloys Compd., 2025, 1037, 182500.
29. S. L. Chiam, H. N. Lim, S. M. Hafiz, A. Pandikumar and N. M. Huang, Sci. Rep., 2018, 8, 3093.
30. G. Xiong, P. He, B. Huang, T. Chen, Z. Bo and T. S. Fisher, Nano Energy, 2017, 38, 127–136.
31. Z. Lin, Y. Liu, Y. Yao, O. J. Hildreth, Z. Li, K. Moon and C. Wong, J. Phys. Chem. C, 2011, 115, 7120–7125.
32. G. Qu, J. Cheng, X. Li, D. Yuan, P. Chen, X. Chen, B. Wang and H. Peng, Adv. Mater., 2016, 28, 3646–3652.
33. K. Subramani, S. Kowsik and M. Sathish, ChemistrySelect, 2016, 1, 3455–3467.
34. K. Sambath Kumar, J. Cherusseri and J. Thomas, ACS Omega, 2019, 4, 4472–4480.
35. G. Pandey, P. W. Menezes and K. Awasthi, Adv. Energy Sustainability Res., 2025, 6, 2500011.
36. G. Pandey, A. Sharma, Meenakshi, K. Pandey, P. W. Menezes and K. Awasthi, ChemCatChem, 2025, 17, e00430.
37. R. Liu, A. Zhou, X. Zhang, J. Mu, H. Che, Y. Wang, T.-T. Wang, Z. Zhang and Z. Kou, Chem. Eng. J., 2021, 412, 128611.
38. T. Wang, H. C. Chen, F. Yu, X. S. Zhao and H. Wang, Energy Storage Mater., 2019, 16, 545–573.
39. J. N. Hausmann and P. W. Menezes, Curr. Opin. Electrochem., 2022, 34, 100991.
40. H. N. Sumedha, J. N. Hausmann, S. Kalra, R. Viswanatha, P. W. Menezes and M. S. Santosh, Ceram. Int., 2023, 49, 1756–1763.
41. K. S. Kumar, N. Choudhary, Y. Jung and J. Thomas, ACS Energy Lett., 2018, 3, 482–495.
42. S. Kamila, M. Kandasamy, B. Chakraborty and B. K. Jena, J. Energy Storage, 2024, 89, 111614.
43. M. Chhowalla, H. S. Shin, G. Eda, L.-J. Li, K. P. Loh and H. Zhang, Nat. Chem., 2013, 5, 263–275.
44. L. Lin, W. Lei, S. Zhang, Y. Liu, G. G. Wallace and J. Chen, Energy Storage Mater., 2019, 19, 408–423.
45. O. Öztürk and E. Gür, ChemElectroChem, 2024, 11, e202300575.
46. C. Tsai, F. Abild-Pedersen and J. K. Nørskov, Nano Lett., 2014, 14, 1381–1387.
47. C. Tsai, K. Chan, F. Abild-Pedersen and J. K. Nørskov, Phys. Chem. Chem. Phys., 2014, 16, 13156–13164.
48. C. Tsai, K. Chan, J. K. Nørskov and F. Abild-Pedersen, Surf. Sci., 2015, 640, 133–140.
49. N. Joseph, P. M. Shafi and A. C. Bose, Energy Fuels, 2020, 34, 6558–6597.
50. M. Ali, A. M. Afzal, M. W. Iqbal, S. Mumtaz, M. Imran, F. Ashraf, A. Ur Rehman and F. Muhammad, Int. J. Energy Res., 2022, 46, 22336–22364.
51. S. Tanwar, A. Arya, A. Gaur and A. L. Sharma, J. Phys.: Condens. Matter, 2021, 33, 303002.
52. R. N. A. R. Seman, M. A. Azam and M. H. Ani, Nanotechnology, 2018, 29, 502001.
53. S. Anna Thomas and J. Cherusseri, J. Energy Chem., 2023, 85, 394–417.
54. Z. Song, Z. Wang and R. Yu, Small Methods, 2023, 8, 2300808.
55. E. S. Sowbakkiyavathi, S. P. Arunachala Kumar, D. K. Maurya, B. Balakrishnan, J. Z. Guo and A. Subramania, Adv. Compos. Hybrid Mater., 2024, 7, 130.
56. A. Philip and A. Ruban Kumar, Renewable Sustainable Energy Rev., 2023, 182, 113423.
57. C. Debbarma, S. Radhakrishnan, S. M. Jeong and C. S. Rout, J. Mater. Chem. A, 2024, 12, 18674–18704.
58. V. V. Mohan, K. P. Revathy, C. B. Adithyan and R. B. Rakhi, J. Energy Storage, 2024, 88, 111505.
59. B. Ali Khan, F. Haider, T. Zhang and S. Zahra, Chem. Rec., 2025, 25, e202500037.
60. T. Ramachandran, M. P. Pachamuthu, R. K. Raji and F. R. M. S. Raj, Mater. Chem. Phys., 2026, 350, 131860.
61. Y. A. Kumar, R. M. N. Kalla, R. Khan, A. G. Al-Sehemi, A. Ghosh, T. Ramachandran and J. Lee, J. Power Sources, 2026, 665, 239027.
62. X. Wu, H. Yang, M. Yu, J. Liu and S. Li, Mater. Today Energy, 2021, 21, 100739.
63. C. Zhong, Y. Deng, W. Hu, J. Qiao, L. Zhang and J. Zhang, Chem. Soc. Rev., 2015, 44, 7484–7539.
64. B. Pal, S. Yang, S. Ramesh, V. Thangadurai and R. Jose, Nanoscale Adv., 2019, 1, 3807–3835.
65. T. S. Bhat, P. S. Patil and R. B. Rakhi, J. Energy Storage, 2022, 50, 104222.
66. A. Muzaffar, M. B. Ahamed, K. Deshmukh and J. Thirumalai, Renewable Sustainable Energy Rev., 2019, 101, 123–145.
67. A. Afif, S. M. Rahman, A. Tasfiah Azad, J. Zaini, M. A. Islan and A. K. Azad, J. Energy Storage, 2019, 25, 100852.
68. J. Libich, J. Máca, J. Vondrák, O. Čech and M. Sedlaříková, J. Energy Storage, 2018, 17, 224–227.
69. B. Xu, F. Wu, S. Chen, C. Zhang, G. Cao and Y. Yang, Electrochim. Acta, 2007, 52, 4595–4598.
70. M. Libber, N. Gariya and M. Kumar, J. Solid State Electrochem., 2025, 29, 513–527.
71. Q. Wang, F. N. Yong, Z. H. Xiao, X. Y. Chen and Z. J. Zhang, J. Electroanal. Chem., 2016, 770, 62–72.
72. N. W. Duffy, W. Baldsing and A. G. Pandolfo, Electrochim. Acta, 2008, 54, 535–539.
73. Q. Wang, Y. F. Nie, X. Y. Chen, Z. H. Xiao and Z. J. Zhang, Electrochim. Acta, 2016, 200, 247–258.
74. M. Ates, A. Chebil, O. Yoruk, C. Dridi and M. Turkyilmaz, Ionics, 2022, 28, 27–52.
75. A. Abdisattar, M. Yeleuov, C. Daulbayev, K. Askaruly, A. Tolynbekov, A. Taurbekov and N. Prikhodko, Electrochem. Commun., 2022, 142, 107373.
76. S. Sundriyal, H. Kaur, S. K. Bhardwaj, S. Mishra, K.-H. Kim and A. Deep, Coord. Chem. Rev., 2018, 369, 15–38.
77. C.-C. Tu, L.-Y. Lin, B.-C. Xiao and Y.-S. Chen, J. Power Sources, 2016, 320, 78–85.
78. B. A. Ali and N. K. Allam, Phys. Chem. Chem. Phys., 2019, 21, 17494–17511.
79. W. Dong, M. Xie, S. Zhao, Q. Qin and F. Huang, Mater. Sci. Eng., R, 2023, 152, 100713.
80. L. L. Zhang and X. S. Zhao, Chem. Soc. Rev., 2009, 38, 2520.
81. J. Zhao and A. F. Burke, J. Energy Chem., 2021, 59, 276–291.
82. S. Alkhalaf, C. K. Ranaweera, P. K. Kahol, K. Siam, H. Adhikari, S. R. Mishra, F. Perez, B. K. Gupta, K. Ramasamy and R. K. Gupta, J. Alloys Compd., 2017, 692, 59–66.
83. J.-G. Wang, Y. Yang, Z.-H. Huang and F. Kang, Carbon, 2013, 61, 190–199.
84. A. G. Pandolfo and A. F. Hollenkamp, J. Power Sources, 2006, 157, 11–27.
85. J. Yan, Q. Wang, T. Wei and Z. Fan, Adv. Energy Mater., 2014, 4, 1300816.
86. M. Y. Perdana, B. A. Johan, M. Abdallah, M. E. Hossain, M. A. Aziz, T. N. Baroud and Q. A. Drmosh, Chem. Rec., 2024, 24, e202400007.
87. S. Sharma and P. Chand, Results Chem., 2023, 5, 100885.
88. S. Aderyani, P. Flouda, S. A. Shah, M. J. Green, J. L. Lutkenhaus and H. Ardebili, Electrochim. Acta, 2021, 390, 138822.
89. P. T. Kissinger and W. R. Heineman, J. Chem. Educ., 1983, 60, 702.
90. R. G. Compton and C. E. Banks, Understanding Voltammetry, WORLD SCIENTIFIC (EUROPE), 2025, pp. 165–204.
91. G. A. Mabbott, J. Chem. Educ., 1983, 60, 697.
92. W. G. Pell and B. E. Conway, J. Power Sources, 2001, 96, 57–67.
93. J. Heinze, Angew. Chem., Int. Ed. Engl., 1984, 23, 831–847.
94. O. A. Farghaly, R. S. A. Hameed and A.-A. H. Abu-Nawwas, Int. J. Electrochem. Sci., 2014, 9, 3287–3318.
95. R. Kumar and M. Bag, J. Phys. Chem. C, 2021, 125, 16946–16954.
96. R. S. Nicholson, Anal. Chem., 1965, 37, 1351–1355.
97. B. Padha, S. Verma, P. Mahajan, V. Gupta, A. Khosla and S. Arya, Crit. Rev. Anal. Chem., 2024, 54, 707–741.
98. X. Yang and A. L. Rogach, Adv. Energy Mater., 2019, 9, 1900747.
99. G. Z. Chen, Int. Mater. Rev., 2017, 62, 173–202.
100. K. C. S. Lakshmi and B. Vedhanarayanan, Batteries, 2023, 9, 202.
101. A. M. Afzal, N. Muzaffar, M. W. Iqbal, G. Dastgeer, A. Manzoor, M. Razaq, S. M. Wabaidur, E. A. Al-Ammar and S. M. Eldin, J. Appl. Electrochem., 2024, 54, 65–76.
102. P. A. Basnayaka, M. K. Ram, L. Stefanakos and A. Kumar, Graphene, 2013, 02, 81–87.
103. J. Shen, J. Ji, P. Dong, R. Baines, Z. Zhang, P. M. Ajayan and M. Ye, J. Mater. Chem. A, 2016, 4, 8844–8850.
104. S. S. Shah, A. Aziz and M. Oyama, in Biomass-Based Supercapacitors, Wiley, 2023, pp. 81–92.
105. V. Sedlakova, J. Sikula, J. Majzner, P. Sedlak, T. Kuparowitz, B. Buergler and P. Vasina, J. Power Sources, 2015, 286, 58–65.
106. K. Panchal, K. Bhakar, K. S. Sharma, D. Kumar and S. Prasad, Appl. Spectrosc. Rev., 2025, 60, 30–55.
107. Y. Jiang and J. Liu, Energy Environ. Mater., 2019, 2, 30–37.
108. R. Yang, Y. Fan, Y. Zhang, L. Mei, R. Zhu, J. Qin, J. Hu, Z. Chen, Y. Hau Ng, D. Voiry, S. Li, Q. Lu, Q. Wang, J. C. Yu and Z. Zeng, Angew. Chem., 2023, 62, e202218016.
109. M. Chhowalla, Z. Liu and H. Zhang, Chem. Soc. Rev., 2015, 44, 2584–2586.
110. P. K. Panda, A. Grigoriev, Y. K. Mishra and R. Ahuja, Nanoscale Adv., 2020, 2, 70–108.
111. H. S. S. Ramakrishna Matte, A. Gomathi, A. K. Manna, D. J. Late, R. Datta, S. K. Pati and C. N. R. Rao, Angew. Chem., Int. Ed., 2010, 49, 4059–4062.
112. K. Belay Ibrahim, T. Ahmed Shifa, S. Zorzi, M. Getaye Sendeku, E. Moretti and A. Vomiero, Prog. Mater. Sci., 2024, 144, 101287.
113. W. Zhao, R. M. Ribeiro and G. Eda, Acc. Chem. Res., 2015, 48, 91–99.
114. N. Choudhary, M. R. Islam, N. Kang, L. Tetard, Y. Jung and S. I. Khondaker, J. Phys.: Condens. Matter, 2016, 28, 364002.
115. M. R. Islam, N. Kang, U. Bhanu, H. P. Paudel, M. Erementchouk, L. Tetard, M. N. Leuenberger and S. I. Khondaker, Nanoscale, 2014, 6, 10033–10039.
116. K. F. Mak, C. Lee, J. Hone, J. Shan and T. F. Heinz, Phys. Rev. Lett., 2010, 105, 136805.
117. W. Choi, N. Choudhary, G. H. Han, J. Park, D. Akinwande and Y. H. Lee, Mater. Today, 2017, 20, 116–130.
118. M. Manikandan, T. Prasankumar, E. Manikandan, E. Papanasam, K. Ramesh and S. Ramesh, Sci. Rep., 2024, 14, 25596.
119. Y.-H. Wu, W.-H. Xia, Y.-Z. Liu, P.-F. Wang, Y.-H. Zhang, J.-R. Huang, Y. Xu, D.-P. Li and L.-J. Ci, Tungsten, 2024, 6, 278–292.
120. E. Pameté, L. Köps, F. A. Kreth, S. Pohlmann, A. Varzi, T. Brousse, A. Balducci and V. Presser, Adv. Energy Mater., 2023, 13, 2301008.
121. Y. Tu, L. Xie, M. Zhang, S. Liu, Z. Luo, L. Wang and Q. Zhao, Nano Res., 2024, 17, 2088–2110.
122. X. Duan and H. Zhang, Chem. Rev., 2024, 124, 10619–10622.
123. M. Kang, B. Kim, S. H. Ryu, S. W. Jung, J. Kim, L. Moreschini, C. Jozwiak, E. Rotenberg, A. Bostwick and K. S. Kim, Nano Lett., 2017, 17, 1610–1615.
124. S. Manzeli, D. Ovchinnikov, D. Pasquier, O. V. Yazyev and A. Kis, Nat. Rev. Mater., 2017, 2, 17033.
125. Y. Jiao, A. M. Hafez, D. Cao, A. Mukhopadhyay, Y. Ma and H. Zhu, Small, 2018, 14, 1800640.
126. X. Zhang, S. Y. Teng, A. C. M. Loy, B. S. How, W. D. Leong and X. Tao, Nanomaterials, 2020, 10, 1012.
127. H. Lin and Y. Meng, J. Mater. Chem. A, 2025, 13, 13585–13601.
128. M. Acerce, D. Voiry and M. Chhowalla, Nat. Nanotechnol., 2015, 10, 313–318.
129. M. B. Askari and P. Salarizadeh, Mater. Renew. Sustain. Energy, 2025, 14, 55.
130. K. Reidy, W. Mortelmans, S. S. Jo, A. N. Penn, A. C. Foucher, Z. Liu, T. Cai, B. Wang, F. M. Ross and R. Jaramillo, Nano Lett., 2023, 23, 5894–5901.
131. D. Lei, Z. Wu, Y. Zhang, Y. Zhang, J. Zhang, J. Xue, X. Peng and Y. Wang, Sep. Purif. Technol., 2024, 332, 125800.
132. S. Zeng, F. Li, C. Tan, L. Yang and Z. Wang, Front. Phys., 2023, 18, 53604.
133. S. Liu, H. Zhang, X. Peng, J. Chen, L. Kang, X. Yin, Y. Yusuke and B. Ding, ACS Nano, 2025, 19, 13591–13636.
134. J. Chen, H. Zhang, X. Peng, X. Shao, Y. Chai, M. Ma, Z. Li, S. Liu and B. Ding, Rare Met., 2025, 44, 8198–8236.
135. S. Rani, M. Sharma, D. Verma, A. Ghanghass, R. Bhatia and I. Sameera, Mater. Sci. Semicond. Process., 2022, 139, 106313.
136. Á. Coogan and Y. K. Gun’ko, Mater. Adv., 2021, 2, 146–164.
137. X. Zhou and G. Yu, ACS Nano, 2021, 15, 11040–11065.
138. S. Alam, M. Asaduzzaman Chowdhury, A. Shahid, R. Alam and A. Rahim, FlatChem, 2021, 30, 100305.
139. J. Wang, G. Li and L. Li, in Two-dimensional Materials – Synthesis, Characterization and Potential Applications, InTech, 2016.
140. N. J. Guido, X. Wang, D. Adalsteinsson, D. McMillen, J. Hasty, C. R. Cantor, T. C. Elston and J. J. Collins, Nature, 2006, 439, 856–860.
141. X. Cao, C. Ding, C. Zhang, W. Gu, Y. Yan, X. Shi and Y. Xian, J. Mater. Chem. B, 2018, 6, 8011–8036.
142. X. Zhang, G. Ma and J. Wang, Tungsten, 2019, 1, 59–79.
143. Z. Wang, C. Zhao, R. Gui, H. Jin, J. Xia, F. Zhang and Y. Xia, Coord. Chem. Rev., 2016, 326, 86–110.
144. J. Zhao, L. Yang, H. Li, T. Huang, H. Cheng, A. Meng, Y. Lin, P. Wu, X. Yuan and Z. Li, Mater. Charact., 2021, 172, 110819.
145. A. M. Bogale, T. Ramachandran, L. T. Tufa, B. B. Badassa, M. E. Suk, R. Pitcheri, J. Lee, S. K. Jilcha, A. Y. Tiky, B. A. Zenebe, N. K. Amare, M. M. Solomon and F. B. Tesema, Mater. Sci. Semicond. Process., 2025, 200, 109958.
146. M. Abdullah, S. Khan, K. Jabbour, M. Imran, M. F. Ashiq, P. John, S. Manzoor, T. Munawar and M. N. Ashiq, Electrochim. Acta, 2023, 466, 143020.
147. Y. Huo, S. Xiu, L.-Y. Meng and B. Quan, Chem. Eng. J., 2023, 451, 138572.
148. J. Lai, W. Niu, R. Luque and G. Xu, Nano Today, 2015, 10, 240–267.
149. K. M. Ø. Jensen, C. Tyrsted, M. Bremholm and B. B. Iversen, ChemSusChem, 2014, 7, 1594–1611.
150. R. Kumar, A. Kumar Keshari, S. Sinha Roy, G. Patel, V. Raju, S. Sain and G. Maity, ChemNanoMat, 2025, 11, e202400584.
151. M. Karuppasamy, D. Muthu, Y. Haldorai and R. T. Rajendra Kumar, Carbon Lett., 2020, 30, 667–673.
152. D. Singh, A. Singh, S. K. Ojha and A. K. Ojha, Synth. Met., 2023, 293, 117263.
153. D. Jin, C. Huang, Y. Xing, W. Fu, W. Lai, L. Wang, H. Zeng, K. Wu and X. Shao, Appl. Surf. Sci., 2025, 705, 163504.
154. J. Zhang, F. Wang, V. B. Shenoy, M. Tang and J. Lou, Mater. Today, 2020, 40, 132–139.
155. Y. Shi, H. Li and L.-J. Li, Chem. Soc. Rev., 2015, 44, 2744–2756.
156. J. Wang, W. Wu, H. Kondo, T. Fan and H. Zhou, Nanotechnology, 2022, 33, 342002.
157. L. Feng, D. Zhao, J. Yu, Q. Zhao, X. Yuan, Y. Liu and S. Guo, JPhys Energy, 2023, 5, 012001.
158. S. Sahoo, A. Al Mahmud, A. Sood, G. Dhakal, S. K. Tiwari, S. Zo, H. M. Kim and S. S. Han, J. Sci.: Adv. Mater. Devices, 2025, 10, 100843.
159. P. N. Bartlett, C. H. K. de Groot, V. K. Greenacre, R. Huang, Y. J. Noori, G. Reid and S. Thomas, Nat. Rev. Chem., 2025, 9, 88–101.
160. R. Sreekumar, A. S. Nair and S. S. Sreejakumari, FlatChem, 2022, 36, 100434.
161. I. Krylova, Prog. Org. Coat., 2001, 42, 119–131.
162. M. Najafi and M. M. Momeni, Chem. Eng. J., 2025, 507, 160555.
163. L. L. Hench and J. K. West, Chem. Rev., 1990, 90, 33–72.
164. V. G. Kessler and G. A. Seisenbaeva, J. Sol-Gel Sci. Technol., 2023, 107, 190–200.
165. R. Wu, H. Zhang, H. Ma, B. Zhao, W. Li, Y. Chen, J. Liu, J. Liang, Q. Qin, W. Qi, L. Chen, J. Li, B. Li and X. Duan, Chem. Rev., 2024, 124, 10112–10191.
166. B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti and A. Kis, Nat. Nanotechnol., 2011, 6, 147–150.
167. H. Li, J. Wu, Z. Yin and H. Zhang, Acc. Chem. Res., 2014, 47, 1067–1075.
168. E. Gao, S.-Z. Lin, Z. Qin, M. J. Buehler, X.-Q. Feng and Z. Xu, J. Mech. Phys. Solids, 2018, 115, 248–262.
169. Z. He and W. Que, Appl. Mater. Today, 2016, 3, 23–56.
170. P. Budania, P. T. Baine, J. H. Montgomery, D. W. McNeill, S. J. Neil Mitchell, M. Modreanu and P. K. Hurley, Micro Nano Lett., 2017, 12, 970–973.
171. A. Jawaid, D. Nepal, K. Park, M. Jespersen, A. Qualley, P. Mirau, L. F. Drummy and R. A. Vaia, Chem. Mater., 2016, 28, 337–348.
172. Y. Xu, H. Cao, Y. Xue, B. Li and W. Cai, Nanomaterials, 2018, 8, 942.
173. J. Shen, Y. He, J. Wu, C. Gao, K. Keyshar, X. Zhang, Y. Yang, M. Ye, R. Vajtai, J. Lou and P. M. Ajayan, Nano Lett., 2015, 15, 5449–5454.
174. D. Lee, B. Lee, K. H. Park, H. J. Ryu, S. Jeon and S. H. Hong, Nano Lett., 2015, 15, 1238–1244.
175. A. Tayyebi, N. Ogino, T. Hayashi and N. Komatsu, Nanotechnology, 2020, 31, 075704.
176. W. Ashraf, A. Khan, S. Bansal and M. Khanuja, Phys. E, 2022, 140, 115152.
177. M. Naghdi, M. Taheran, S. K. Brar, T. Rouissi, M. Verma, R. Y. Surampalli and J. R. Valero, J. Cleaner Prod., 2017, 164, 1394–1405.
178. H. Wu, W. Zhao, H. Hu and G. Chen, J. Mater. Chem., 2011, 21, 8626.
179. L. Dong, J. Qiu, J. Zhang, Y. Wang, Y. Han, Y. Liu, D. Li, J. Feng and H. Peng, Electrochim. Acta, 2025, 525, 146117.
180. P. Yu, W. Fu, Q. Zeng, J. Lin, C. Yan, Z. Lai, B. Tang, K. Suenaga, H. Zhang and Z. Liu, Adv. Mater., 2017, 29, 1701909.
181. N. Choudhary, C. Li, H.-S. Chung, J. Moore, J. Thomas and Y. Jung, ACS Nano, 2016, 10, 10726–10735.
182. S. Mukherjee, J. Turnley, E. Mansfield, J. Holm, D. Soares, L. David and G. Singh, R. Soc. Open Sci., 2019, 6, 190437.
183. R. Chaturvedi and A. Garg, Bull. Mater. Sci., 2024, 47, 220.
184. Neetika, A. Sanger, V. K. Malik and R. Chandra, Int. J. Hydrogen Energy, 2018, 43, 11141–11149.
185. L. Jiang, S. Zhang, S. A. Kulinich, X. Song, J. Zhu, X. Wang and H. Zeng, Mater. Res. Lett., 2015, 3, 177–183.
186. Y. Yang, H. Fei, G. Ruan, C. Xiang and J. M. Tour, Adv. Mater., 2014, 26, 8163–8168.
187. D. Li, W. Zhou, Q. Zhou, G. Ye, T. Wang, J. Wu, Y. Chang and J. Xu, Nanotechnology, 2017, 28, 395401.
188. A. Ramadoss, T. Kim, G.-S. Kim and S. J. Kim, New J. Chem., 2014, 38, 2379.
189. X. Wang, J. Ding, S. Yao, X. Wu, Q. Feng, Z. Wang and B. Geng, J. Mater. Chem. A, 2014, 2, 15958–15963.
190. L.-M. Xu, L. Ma, X.-Y. Xu, X.-P. Zhou, L.-L. Zhang and W.-X. Chen, Mater. Lett., 2016, 173, 84–87.
191. L.-Z. Bai, F. Li, D. An, J.-F. Wei, Z.-Y. Zhang and Y.-Q. Liu, J. Nanosci. Nanotechnol., 2018, 18, 1804–1810.
192. P. Wang, C. Zhou, B. Zheng, H. Liu, S. Sun and D. Guo, Mater. Lett., 2018, 233, 286–289.
193. H. Gupta, S. Chakrabarti, S. Mothkuri, B. Padya, T. N. Rao and P. K. Jain, Mater. Today: Proc., 2020, 26, 20–24.
194. S. S. Karade, D. P. Dubal and B. R. Sankapal, RSC Adv., 2016, 6, 39159–39165.
195. R. Patel, A. I. Inamdar, H. B. Kim, H. Im and H. Kim, J. Korean Phys. Soc., 2016, 68, 1341–1346.
196. R. B. Pujari, A. C. Lokhande, A. R. Shelke, J. H. Kim and C. D. Lokhande, J. Colloid Interface Sci., 2017, 496, 1–7.
197. A. M. Abraham, S. P. Lonkar, V. V. Pillai and S. M. Alhassan, ACS Omega, 2020, 5, 11721–11729.
198. M. A. Bissett, S. D. Worrall, I. A. Kinloch and R. A. W. Dryfe, Electrochim. Acta, 2016, 201, 30–37.
199. K. Krishnamoorthy, P. Pazhamalai, G. K. Veerasubramani and S. J. Kim, J. Power Sources, 2016, 321, 112–119.
200. H. D. Yoo, Y. Li, Y. Liang, Y. Lan, F. Wang and Y. Yao, ChemNanoMat, 2016, 2, 688–691.
201. Y. Xie and P. Sun, J. Nanopart. Res., 2018, 20, 183.
202. C. Liu, X. Zhao, S. Wang, Y. Zhang, W. Ge, J. Li, J. Cao, J. Tao and X. Yang, ACS Appl. Energy Mater., 2019, 2, 4458–4463.
203. M. Mohan, K. N. N. Unni and R. B. Rakhi, Vacuum, 2019, 166, 335–340.
204. S. Wei, R. Zhou and G. Wang, ACS Omega, 2019, 4, 15780–15788.
205. M. F. Koudahi and E. Frąckowiak, Energy Storage Mater., 2022, 49, 255–267.
206. S. S. Singha, S. Rudra, S. Mondal, M. Pradhan, A. K. Nayak, B. Satpati, P. Pal, K. Das and A. Singha, Electrochim. Acta, 2020, 338, 135815.
207. F. N. I. Sari and J.-M. Ting, Sci. Rep., 2017, 7, 5999.
208. Q. Ji, C. Li, J. Wang, J. Niu, Y. Gong, Z. Zhang, Q. Fang, Y. Zhang, J. Shi, L. Liao, X. Wu, L. Gu, Z. Liu and Y. Zhang, Nano Lett., 2017, 17, 4908–4916.
209. A. Lamberti and C. F. Pirri, J. Energy Storage, 2016, 8, 193–197.
210. L. E. Conroy and K. C. Park, Inorg. Chem., 1968, 7, 459–463.
211. J. Park, S. J. Kim, K. Lim, J. Cho and K. Kang, ACS Energy Lett., 2022, 7, 3718–3726.
212. G. A. Muller, J. B. Cook, H.-S. Kim, S. H. Tolbert and B. Dunn, Nano Lett., 2015, 15, 1911–1917.
213. A. D. Ucar, S. K. Baglicakoglu, M. B. Durukan, M. Cugunlular, S. Oz, Y. Kocak, B. Ülgüt, E. Ozensoy and H. E. Unalan, Mater. Today Energy, 2025, 48, 101810.
214. Q. Wang, S. Wang, J. Li, L. Ruan, N. Wei, L. Huang, Z. Dong, Q. Cheng, Y. Xiong and W. Zeng, Adv. Electron. Mater., 2020, 6, 2000388.
215. P. Zhou, L. Fan, J. Wu, C. Gong, J. Zhang and Y. Tu, J. Alloys Compd., 2016, 685, 384–390.
216. M. Abdullah, P. John, S. Manzoor, M. I. Ghouri, H. H. Hegazy, A. H. Chugtai, S. Aman, A. M. Shawky, M. N. Ashiq and T. A. Taha, J. Energy Storage, 2022, 56, 105929.
217. M. Habib, S. Ullah, F. Khan, M. I. Rafiq, A. Salem Balobaid, T. Alshahrani and Z. Muhammad, Mater. Sci. Eng., B, 2023, 298, 116904.
218. V. Gokulsaswath, G. Suganya, S. Monika and G. Kalpana, Cryst. Res. Technol., 2024, 59, 2300111.
219. R. Samal and C. S. Rout, Adv. Mater. Interfaces, 2020, 7, 1901682.
220. A. B. Nandana and R. B. Rakhi, Energy Technol., 2025, 13, 2402153.
221. J. Feng, X. Sun, C. Wu, L. Peng, C. Lin, S. Hu, J. Yang and Y. Xie, J. Am. Chem. Soc., 2011, 133, 17832–17838.
222. B. Mohan, U. Boruah, R. Sonkar, N. J. Mondal and D. Chowdhury, Part. Part. Syst. Charact., 2025, 42, 2400156.
223. S. S. Nardekar, K. Krishnamoorthy, P. Pazhamalai, S. Sahoo, V. K. Mariappan and S.-J. Kim, J. Mater. Chem. A, 2020, 8, 13121–13131.
224. S. Mishra, P. K. Maurya and A. K. Mishra, Mater. Chem. Phys., 2020, 255, 123551.
225. S. V. P. Vattikuti, K. C. Devarayapalli, P. C. Nagajyothi and J. Shim, Microchem. J., 2020, 153, 104446.
226. S. Upadhyay and O. P. Pandey, J. Alloys Compd., 2021, 857, 157522.
227. D. Vikraman, S. Hussain, K. Karuppasamy, P. Santhoshkumar, A. Kathalingam, J. Jung and H. Kim, Int. J. Energy Res., 2022, 46, 18410–18425.
228. N. Bahadursha, G. Bansal, A. Tiwari, A. Bhattacharjee and S. Kanungo, Phys. E, 2024, 159, 115936.
229. V. V. Mohan, M. Manuraj, P. M. Anjana and R. B. Rakhi, Energy Technol., 2022, 10, 2100976.
230. C. Lee, B. G. Jeong, S. J. Yun, Y. H. Lee, S. M. Lee and M. S. Jeong, ACS Nano, 2018, 12, 9982–9990.
231. M. I. A. Abdel Maksoud, R. A. Fahim, A. E. Shalan, M. Abd Elkodous, S. O. Olojede, A. I. Osman, C. Farrell, A. H. Al-Muhtaseb, A. S. Awed, A. H. Ashour and D. W. Rooney, Environ. Chem. Lett., 2021, 19, 375–439.
232. S. Ratha and C. S. Rout, ACS Appl. Mater. Interfaces, 2013, 5, 11427–11433.
233. Z. Li, J. Yu, C. Shi, H. Su and L. Bai, J. Energy Storage, 2024, 91, 112082.
234. R. Browning, N. Kuperman, R. Solanki, V. Kanzyuba and S. Rouvimov, Semicond. Sci. Technol., 2016, 31, 095002.
235. J. Wang, Y. Zhao, C. He, K. Li, Z. Wang, J. Liu, Q. Zhang, N. Mao and Y. Cao, Electrochim. Acta, 2024, 477, 143819.
236. C. Yin, T. Zhang, C. Zhang, Y. Zhang, C. K. Jeong, G. Hwang and Q. Chi, SusMat, 2024, 4, e228.
237. F. Faisal, B. M. Alotaibi, A. Gassoumi, H. A. Alyousef, A. W. Alrowaily, N. Al-Harbi, M. J. Khan and K. Ahmad, Electrochim. Acta, 2024, 505, 144876.
238. T. Sruthi and V. Mathew, AIP Conf. Proc., 2024, 3196, 030004.
239. A. Tomar, S. Issar, N. Choudhary, S. Kodan and R. Chandra, Energy Fuels, 2024, 38, 13425–13435.
240. J.-C. Xing, Y.-L. Zhu, Q.-W. Zhou, X.-D. Zheng and Q.-J. Jiao, Electrochim. Acta, 2014, 136, 550–556.
241. R. Ren, M. S. Faber, R. Dziedzic, Z. Wen, S. Jin, S. Mao and J. Chen, Nanotechnology, 2015, 26, 494001.
242. L. Han, S. Cui, Y. Gu, Y. Tang, W. Cui, G. Li and Q. Zhang, Chem. Eng. J., 2025, 512, 162326.
243. H. Mao, J. Yu, J. Li, T. Zheng, J. Cen and Y. Ye, Ceram. Int., 2020, 46, 6991–6994.
244. Z. Dai, X. Zang, J. Yang, C. Sun, W. Si, W. Huang and X. Dong, ACS Appl. Mater. Interfaces, 2015, 7, 25396–25401.
245. Z. Dai, L. Xue, Z. Zhang, Y. Gao, J. Wang, Q. Gao and D. Chen, Energy Fuels, 2020, 34, 10178–10187.
246. N. S. Arul and J. I. Han, Mater. Lett., 2016, 181, 345–349.
247. S. Wang, W. Li, L. Xin, M. Wu, Y. Long, H. Huang and X. Lou, Chem. Eng. J., 2017, 330, 1334–1341.
248. F. Zhang, T. Eom, M. Cho, H.-J. Lee and H. Pang, J. Energy Storage, 2021, 42, 103098.
249. M. Manikandan, K. Subramani, M. Sathish and S. Dhanuskodi, ChemistrySelect, 2018, 3, 9034–9040.
250. R. Kumar, A. K. Shringi, H. J. Wood, I. M. Asuo, S. Oturak, D. E. Sanchez, T. S. K. Sharma, R. Chaurasiya, A. Mishra, W. M. Choi, N. Y. Doumon, I. Dabo, M. Terrones and F. Yan, Mater. Sci. Eng., R, 2025, 163, 100946.
251. D. Vikraman, S. Hussain, K. Karuppasamy, A. Kathalingam, E.-B. Jo, A. Sanmugam, J. Jung and H.-S. Kim, J. Alloys Compd., 2022, 893, 162271.
252. P. Kour, S. Kour, Deeksha, A. L. Sharma and K. Yadav, J. Alloys Compd., 2024, 981, 173740.
253. I. T. Bello, K. O. Otun, G. Nyongombe, O. Adedokun, G. L. Kabongo and M. S. Dhlamini, Int. J. Energy Res., 2022, 46, 8908–8918.
254. M. Isacfranklin, L. E. M. Princy, Y. Rathinam, L. Kungumadevi, G. Ravi, A. G. Al-Sehemi and D. Velauthapillai, Energy Fuels, 2022, 36, 6476–6482.
255. K. A. S. Raj and C. S. Rout, Emergent Mater., 2021, 4, 1037–1046.
256. M. Z. Iqbal, A. Bibi, A. Khizar, N. Badi, H. H. Hegazy and A. A. Alahmari, J. Electroanal. Chem., 2024, 975, 118738.
257. R. Samal, P. Mane, B. Chakraborty, D. Late and C. S. Rout, Int. J. Energy Res., 2022, 46, 24588–24601.
258. Q. Akbar Sial, G. Mohapatra, R. Basit Ali, M. Waqas Khan, M. Waqas, A. Kumar and H. Seo, Chem. Eng. J., 2025, 503, 158368.
259. M. R. Charapale, U. V. Shembade, S. A. Ahir, V. P. Kothavale, N. T. Jadhav, V. G. Sankpal, P. P. Waifalkar, A. V. Moholkar, T. D. Dongale and S. A. Masti, Surf. Interfaces, 2024, 52, 104814.
260. H. Mahajan, K. U. Mohanan and S. Cho, Nano Lett., 2022, 22, 8161–8167.
261. S. C. Kishore, R. Atchudan, S. Perumal, T. N. J. I. Edison, A. K. Sundramoorthy, R. Vinodh, M. Alagan and Y. R. Lee, J. Nanostruct. Chem., 2023, 13, 545–561.
262. D. Vikraman, S. Hussain, I. Rabani, A. Feroze, M. Ali, Y.-S. Seo, S.-H. Chun, J. Jung and H.-S. Kim, Nano Energy, 2021, 87, 106161.
263. S. K. Das, L. Pradhan, B. K. Jena and S. Basu, Carbon, 2023, 201, 49–59.
264. K. K. Jena, A. T. Mayyas, B. Mohanty, B. K. Jena, J. R. Jos, A. AlFantazi, B. Chakraborty and A. A. Almarzooqi, Energy Fuels, 2022, 36, 2159–2170.
265. G. Nabi, K. N. Riaz, M. Nazir, W. Raza, M. B. Tahir, M. Rafique, N. Malik, A. Siddiqa, S. S. Ali Gillani, M. Rizwan, M. Shakil and M. Tanveer, Ceram. Int., 2020, 46, 27601–27607.
266. J. Tang, X. Huang, T. Lin, T. Qiu, H. Huang, X. Zhu, Q. Gu, B. Luo and L. Wang, Energy Storage Mater., 2020, 26, 550–559.
267. H. Iqbal, B. Parveen, S. Kiran, M. Imran, F. Saddique, M. U. Hassan and A. Razaq, J. Mater. Sci.: Mater. Electron., 2022, 33, 24845–24856.
268. U. Rana, S. Aman, M. N. Ashiq, M. F. Iqbal, S. Manzoor, M. H. H. Mahmoud, A. Alhadhrami, H. O. Elansry, D. O. El-Ansari and T. A. Taha, J. Sol-Gel Sci. Technol., 2022, 103, 704–712.
269. M. Imtiaz, A. W. Alrowaily, A. Dahshan, H. A. Alyousef, B. M. Alotaibi, M. F. Alotiby, M. J. Khan and K. Ahmad, Diam. Relat. Mater., 2024, 148, 111484.
270. W. A. Haider, M. Tahir, L. He, W. Yang, A. Minhas-khan, K. A. Owusu, Y. Chen, X. Hong and L. Mai, J. Alloys Compd., 2020, 823, 151769.
271. F. Wei, Y. Li, H. Wang, T. Shu, J. Yuan, G. Lu, B. Lin, Z. Gao, Q. Wang, J. Qi and Y. Sui, J. Energy Storage, 2023, 60, 106551.
272. M. Tobis, S. Sroka and E. Frąckowiak, Front. Energy Res., 2021, 9, 647878.
273. S. Kapse, B. Benny, P. Mandal and R. Thapa, J. Energy Storage, 2021, 44, 103476.
274. S. S. Magdum, S. Thangarasu and T. H. Oh, Inorganics, 2022, 10, 229.
275. T. Lin, T. Sadhasivam, A. Wang, T. Chen, J. Lin and L. Shao, ChemElectroChem, 2018, 5, 1024–1031.
276. J. Wang, S. Li, N. Fu, D. Tian, Y. Zheng, F. Wang, C. Liu, X. Wang, Z. Zhou, Y. Niu, H. Liu, G. Wang, S. Mu and J. Luo, Adv. Compos. Hybrid Mater., 2025, 8, 190.
277. W. Han, L. Yuan, X. Liu, C. Wang and J. Li, J. Electroanal. Chem., 2021, 899, 115643.
278. S. Tanwar and A. L. Sharma, Ceram. Int., 2023, 49, 18281–18295.
279. C. Li, Y. Zhou, P. Huo and X. Wang, J. Alloys Compd., 2020, 826, 154175.
280. J. Gao, Y. Hao, S. Lin, Z. Zhang, H. Li and Y. He, Chem. Eng. J., 2025, 504, 158572.
281. Y. Li, X. Xiao, F. Yang and C. An, ACS Appl. Energy Mater., 2022, 5, 10680–10689.
282. S. Sarwar, Z. Liu, J. Li, Y. Wang, R. Wang and X. Zhang, J. Alloys Compd., 2020, 846, 155886.
283. H.-J. Zhang, Q.-C. Jia and L.-B. Kong, J. Energy Storage, 2022, 47, 103617.
284. M. Samtham, D. Singh, K. Hareesh and R. S. Devan, J. Energy Storage, 2022, 51, 104418.
285. Q. Chen, F. Xie, G. Wang, K. Ge, H. Ren, M. Yan, Q. Wang and H. Bi, Ionics, 2021, 27, 4083–4096.
286. A. Sajedi-Moghaddam, C. C. Mayorga-Martinez, E. Saievar-Iranizad, Z. Sofer and M. Pumera, Appl. Mater. Today, 2019, 16, 280–289.
287. M. Amini and B. Azadegan, Materialia, 2023, 32, 101907.
288. G. Nabi, A. Hussain, W. Ali, M. Alam, M. Tanveer, F. Naseem, A. H. Bhalli, H. Ahmed, N. S. Arshad and S. Muzaffar, Solid State Ionics, 2024, 413, 116618.
289. Y. Gao, Y. Jiang, B. Cai, H. Gu, R. Xu, Y. Sun, J. Zhou and F. Yu, ACS Appl. Energy Mater., 2025, 8, 1671–1682.
290. D. Xiong, X. Li, Z. Bai and S. Lu, Small, 2018, 14, 1703419.
291. M. Alhabeb, K. Maleski, B. Anasori, P. Lelyukh, L. Clark, S. Sin and Y. Gogotsi, Chem. Mater., 2017, 29, 7633–7644.
292. D. N. Ampong, E. Agyekum, F. O. Agyemang, K. Mensah-Darkwa, A. Andrews, A. Kumar and R. K. Gupta, Discover Nano, 2023, 18, 3.
293. S. Raj KA, P. Mane, S. Radhakrishnan, B. Chakraborty and C. S. Rout, ACS Appl. Nano Mater., 2022, 5, 4423–4436.
294. Y. Xiao, Y. Kong, X. Wang, H. Luo, G. Yuan, S. Zhang, A. Zhang, J. Zhou, Y. Fan, L. Xin, A. Wang, S. Fang and Y. Zheng, J. Colloid Interface Sci., 2025, 677, 577–586.
295. M. M. Gul, K. S. Ahmad, A. G. Thomas and A. M. Tighezza, Mater. Sci. Eng., B, 2024, 303, 117340.
296. L. Wang, X. Zhang, Y. Ma, M. Yang and Y. Qi, J. Phys. Chem. C, 2017, 121, 9089–9095.
297. M. Iqbal, N. G. Saykar, A. Kumar Mahanta and S. K. Mahapatra, Mater. Today: Proc., 2022, 67, 762–767.
298. A. B. Patel, J. V. Vaghasiya, P. Chauhan, C. K. Sumesh, V. Patel, S. S. Soni, K. D. Patel, P. Garg, G. K. Solanki and V. M. Pathak, Nanoscale, 2022, 14, 6636–6647.
299. M. Nagaraju, B. Ramulu, A. S. Kiran and J. S. Yu, J. Mater. Chem. A, 2024, 12, 13446–13457.
300. H. Gholami Shamami, A. Mohammadi Zardkhoshoui and S. S. Hosseiny Davarani, Nanoscale, 2025, 17, 4591–4602.
301. J. Liu, L. Ren, J. Luo and J. Song, Colloids Surf., A, 2022, 647, 129093.
302. S. P. Vinodhini and J. R. Xavier, Int. J. Energy Res., 2022, 46, 14088–14104.
303. P. Siddu, S. R. K A, S. Radhakrishnan, S. Mun Jeong and C. Sekhar Rout, Batteries Supercaps, 2025, 8, e202400466.
304. H. Su, C. Niu, R. Zhang, M. Huang and Z. Li, J. Alloys Compd., 2025, 1010, 178074.
305. M. A. Qadeer, A. R. Ali, M. Tanveer, S. Yasmeen, G. Nabi, H. H. Cheema, R. H. Alshammari and H. A. Sakr, Ceram. Int., 2024, 50, 43477–43489.
306. M. A. Rahman, M. A. Haque, M. A. A. Shaikh, C. K. Roy, A. H. Reaz, M. T. A. Shawon, P. K. Baksi, S. Yasmin, M. H. Kabir, S. H. Won, T. W. Kim and M. M. Rahman, J. Energy Storage, 2024, 99, 113205.
307. L. Wen, Y. Wu, S. Wang, J. Shi, Q. Zhang, B. Zhao, Q. Wang, C. Zhu, Z. Liu, Y. Zheng, J. Su and Y. Gao, Nano Energy, 2022, 93, 106896.
308. M. Habib, Z. Muhammad, Y. A. Haleem, S. Farooq, R. Nawaz, A. Khalil, F. Shaheen, H. Naeem, S. Ullah and R. Khan, Mater. Adv., 2024, 5, 1088–1098.
309. T. M. Masikhwa, F. Barzegar, J. K. Dangbegnon, A. Bello, M. J. Madito, D. Momodu and N. Manyala, RSC Adv., 2016, 6, 38990–39000.
310. K. Rajendran, P. Nagamony and H. Annal Therese, Phys. Status Solidi, 2022, 219, 2200203.
311. W. Li, X. Wei, H. Dong, Y. Ou, S. Xiao, Y. Yang, P. Xiao and Y. Zhang, Front. Chem., 2020, 8, 189.
312. P. A. Shinde, N. R. Chodankar, H.-J. Kim, M. A. Abdelkareem, A. Al Ghaferi, Y.-K. Han, A. G. Olabi and K. Ariga, ACS Energy Lett., 2023, 8, 4474–4487.
313. A. Tomar, N. Choudhary, G. Malik and R. Chandra, ACS Appl. Nano Mater., 2024, 7, 26111–26125.
314. T. Chen, S. Li, J. Wen, P. Gui, Y. Guo, C. Guan, J. Liu and G. Fang, Small, 2018, 14, 1700979.
315. G. Nabi, W. Ali, M. Tanveer, T. Iqbal, M. Rizwan and S. Hussain, J. Energy Storage, 2023, 58, 106316.
316. S. P. Vinodhini and J. R. Xavier, Mater. Sci. Eng., B, 2023, 291, 116375.
317. A. Panagiotopoulos, G. Nagaraju, S. Tagliaferri, C. Grotta, P. C. Sherrell, M. Sokolikova, G. Cheng, F. Iacoviello, K. Sharda and C. Mattevi, J. Mater. Chem. A, 2023, 11, 16190–16200.
318. J. R. Xavier, Mater. Sci. Eng., B, 2025, 312, 117856.
319. B. Pandit, S. S. Karade and B. R. Sankapal, ACS Appl. Mater. Interfaces, 2017, 9, 44880–44891.
320. Z. Zhang, X. Huang, H. Wang, S. H. Teo and T. Ma, J. Alloys Compd., 2019, 771, 274–280.
321. A. Sharma, S. Kapse, A. Verma, S. Bisoyi, G. K. Pradhan, R. Thapa and C. S. Rout, ACS Appl. Energy Mater., 2022, 5, 10315–10327.
322. K. A. Sree Raj, A. S. Shajahan, B. Chakraborty and C. S. Rout, Chem.–Eur. J., 2020, 26, 6662–6669.
323. S. R. K A, K. Pramoda and C. S. Rout, J. Mater. Chem. C, 2023, 11, 2565–2573.
324. H. K. Rathore, M. Hariram, M. K. Ganesha, A. K. Singh, D. Das, M. Kumar, K. Awasthi and D. Sarkar, Sustainable Energy Fuels, 2023, 7, 2613–2626.
325. S. R. K A, A. S. Shajahan, B. Chakraborty and C. S. Rout, RSC Adv., 2020, 10, 31712–31719.
326. S. R. Marri, S. Ratha, C. S. Rout and J. N. Behera, Chem. Commun., 2017, 53, 228–231.
327. J. Xu, S. Zhang, Z. Wei, W. Yan, X. Wei and K. Huang, J. Colloid Interface Sci., 2021, 585, 12–19.
328. S. Radhakrishnan, M. Monisha, S. R. K A, M. Saxena, S. M. Jeong and C. S. Rout, Adv. Sustainable Syst., 2025, 9, 2400529.
329. H. Hassan, M. W. Iqbal, N. Ahmad, N. H. Al-Shaalan, S. Alharthi, N. D. Alqarni, M. A. Amin, A. M. Afzal, M. Aljohani and M. Z. Ansari, Diam. Relat. Mater., 2024, 141, 110687.
330. G. Song, J. Li, C. Dong, P. Zhang, M. Yang, S. Park, T. Zhang, M. Wang, H. Shi, Q. Liu, J. Gu and X. Feng, J. Mater. Chem. A, 2023, 11, 11153–11160.
331. M. Hussain, A. M. M. Abdelbacki, M. Saleem, M. Aslam and M. Ali, J. Phys. Chem. Solids, 2025, 196, 112354.
332. K. Gupta, N. Singh, R. S. Singh, U. P. Azad and A. K. Singh, J. Energy Storage, 2024, 103, 114348.
333. M. Z. Iqbal, M. Alzaid, U. Abbasi, S. Alam, R. Ali, A. M. Afzal and S. Aftab, Int. J. Energy Res., 2022, 46, 7334–7347.
334. E. Moradpur-Tari, R. Sarraf-Mamoory and A. Yourdkhani, Ceram. Int., 2022, 48, 8563–8571.
335. V. Shrivastav, S. Sundriyal, V. Shrivastav, U. K. Tiwari and A. Deep, Energy Fuels, 2021, 35, 15133–15142.
336. S. Hussain, I. Rabani, D. Vikraman, A. Feroze, M. Ali, Y.-S. Seo, H.-S. Kim, S.-H. Chun and J. Jung, Nanomaterials, 2020, 10, 1597.
337. C. E. L. dos Santos, J. E. S. Fonsaca, T. P. Vello, M. M. Oliveira and S. H. Domingues, Synth. Met., 2025, 311, 117843.
338. M. Z. Iqbal, H. Tariq, A. Zakir, A. Khizar, A. Kumar and M. A. Khan, J. Phys. Chem. Solids, 2025, 197, 112425.
339. P. T. Pınar, M. Gülcan and Y. Yardım, J. Alloys Compd., 2025, 1010, 177656.
340. D. Krishnamoorthy and A. K. Singh, Diam. Relat. Mater., 2025, 152, 111976.
341. L. Wang, C. Zhang, X. Cao, X. Xu, J. Bai, R. Li and T. Satoh, J. Energy Storage, 2025, 108, 115153.
342. M. Ali, S. D. Alahmari, S. A. M. Abdelmohsen, M. M. Alanazi, A. G. Al-Sehemi, M. Abdullah, S. Aman and H. M. T. Farid, Ceram. Int., 2024, 50, 6931–6940.
343. S. Hussain, D. Vikraman, M. T. Mehran, M. Hussain, G. Nazir, S. A. Patil, H.-S. Kim and J. Jung, Renewable Energy, 2022, 185, 585–597.
344. D. Singh, S. K. Ojha, A. Maurya, T. Preitschopf, I. Fischer and A. K. Ojha, J. Alloys Compd., 2023, 968, 171828.
345. M. Xia, J. Ning, D. Wang, X. Feng, B. Wang, H. Guo, J. Zhang and Y. Hao, Chem. Eng. J., 2021, 405, 126611.
346. A. Khaliq, S. Gouadria, X. Yang, S. Xu, J. Zha and B. Luo, JOM, 2025, 77, 2580–2589.
347. N. Ahmad, P. Kanjariya, A. Rajiv, A. Kumar, A. Shankhyan, S. Jaidka, S. Kulshrestha, A. Kumar and M. Al-hedrewy, Inorg. Chem. Commun., 2025, 172, 113789.
348. P. Chauhan, A. B. Patel, G. K. Solanki, C. K. Sumesh, S. S. Soni, D. J. Late, V. Patel and V. M. Pathak, Mater. Today Chem., 2022, 26, 101079.
349. N. Akhtar, N. Muzaffar, M. Imran, A. M. Afzal, M. W. Iqbal, S. Safdar, A. A. A. Bahajjaj, S. Mumtaz, M. Z. Iqbal and M. Azeem, Phys. Scr., 2024, 99, 125992.
350. A. Sarkar, A. K. Chakraborty, S. Bera and S. Krishnamurthy, J. Phys. Chem. C, 2018, 122, 18237–18246.
351. B. Dasgupta, D. Bagchi, T. Sontheimer, M. Driess and P. W. Menezes, Nat. Rev. Chem., 2025, 9, 766–789.
352. S. Ghosh, D. Bagchi, I. Mondal, T. Sontheimer, R. V. Jagadeesh and P. W. Menezes, Adv. Energy Mater., 2024, 14, 2400696.
353. B. Dasgupta, S. Yao, I. Mondal, S. Mebs, J. Schmidt, K. Laun, I. Zebger, H. Dau, M. Driess and P. W. Menezes, ACS Nano, 2024, 18, 33964–33976.

---