Tailoring the Pseudocapacitive Performance of Hierarchical α-MoO 3 /CoS 2 Nanostructures for Enhanced Electrochemical Properties of Aqueous Symmetric Supercapacitors

Abstract

In this study, α-MoO 3 /CoS 2 nanocomposites with varying CoS 2 contents (0-7% wt) were synthesized using a one-step hydrothermal method to investigate the effect of CoS 2 incorporation into α-MoO 3 and to identify the optimal composition for enhanced electrochemical energy storage performance. Among the synthesized nanomaterials, the α-MoO 3 /CoS 2 with 5% wt CoS 2 exhibited the highest specific capacitance of 553 Fg⁻¹ at a current density of 0.5 Ag⁻¹ in a three-electrode setup, significantly outperforming α-MoO 3 , which delivered 216 Fg⁻¹. Additionally, the optimized nanocomposite, α-MoO 3 /CoS 2 (5% wt) retained 82.1% of its initial capacitance after 5,000 charge-discharge cycles at 5 Ag⁻¹, indicating excellent cycling stability. Morphological and structural investigations showed that the enhanced electrochemical behavior of α-MoO 3 stemmed from the presence of surface-active sites associated with structural defects and enlarged interlayer distance, which collectively facilitated efficient ion adsorption, promoted interlayer ion intercalation, and accelerated surface redox reactions. Furthermore, the α-MoO 3 /CoS 2 (5% wt) nanocomposite exhibited enhanced charge-transfer kinetics, reflecting suppressed interfacial charge-transfer resistance and resulting in a higher specific capacitance. Additionally, symmetric supercapacitors based on the α-MoO 3 /CoS 2 (5% wt) nanocomposite achieved a high energy density of 25.09 Whkg -1 at a power density of 901 Wkg -1 , successfully powering a red LED for 290 seconds. The device exhibited outstanding long-term electrochemical stability, preserving 97% of its original capacitance after 5,000 consecutive charge-discharge cycles. The results demonstrate that the incorporation of conductive CoS 2 significantly improves the electrochemical performance of α-MoO 3 , indicating its suitability for next-generation energy storage devices.