Hydrothermally synthesized 2H-WS2 nanorods for improved supercapacitor electrode performance

Abstract

We demonstrate an emerging and versatile hydrothermal process at three different temperatures (220, 230 and 240 °C) for producing one-dimensional (1D) WS₂ nanorods, which can be easily scaled up. The crystallography, morphology, stoichiometry, lattice-scale and textural features confirmed that the obtained WS₂ products were structurally uniform. Furthermore, the as-synthesized WS₂ nanorods at 240 °C (WS₂₄₀) exhibited enhanced specific surface area, average pore size, charge transport and electrochemical stability compared with WS₂₂₀ and WS₂₃₀ products. Moreover, the cyclic voltammetry study of WS₂₄₀ nanorods indicated diffusion-controlled charge storage with the highest peak current and capacitance retention of approximately 95.8% after 10 000 cycles. The galvanostatic charge–discharge curves revealed a faster kinetics and prolonged cycling stability. Additionally, electrochemical impedance spectroscopy exhibited the lowest charge transfer resistance (10.23 Ω) and improved ion diffusion, indicating rapid redox reactions in WS₂₄₀. The maximum specific capacitance of 271.6 F g⁻¹ at 5 mV s⁻¹ was exhibited by the WS₂ electrode. Density functional theory investigations revealed a considerable reduction in the HOMO–LUMO energy gap from 1.153 eV to 0.668 eV, enhancing the electronic conductivity behaviour. The effectiveness of the KOH electrolyte with WS₂ was studied in terms of the parametric enhancement after K⁺ ion integration into the WS₂ structure. In a nutshell, this study presents a facile and cost-effective approach for synthesizing WS₂ nanorods at 240 °C via a hydrothermal approach, highlighting their promising potential as economically viable supercapacitors and hybrid energy storage systems.