Tailoring the pseudocapacitive performance of hierarchical α-MoO3/CoS2 nanostructures for enhanced electrochemical properties of aqueous symmetric supercapacitors

In this study, α-MoO₃/CoS₂ nanocomposites with varying CoS₂ contents (0–7% wt) were synthesized using a one-step hydrothermal method to investigate the effect of CoS₂ incorporation into α-MoO₃ and to identify the optimal composition for enhanced electrochemical energy storage performance. Among the synthesized nanomaterials, the α-MoO₃/CoS₂ with 5% wt CoS₂ exhibited the highest specific capacitance of 553 F g⁻¹ at a current density of 0.5 A g⁻¹ in a three-electrode setup, significantly outperforming α-MoO₃, which delivered 216 F g⁻¹. Additionally, the optimized nanocomposite, α-MoO₃/CoS₂ (5% wt) retained 82.1% of its initial capacitance after 5000 charge–discharge cycles at 5 A g⁻¹, indicating excellent cycling stability. Morphological and structural investigations showed that the enhanced electrochemical behavior of α-MoO₃ 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-MoO₃/CoS₂ (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-MoO₃/CoS₂ (5% wt) nanocomposite achieved a high energy density of 25.09 Wh kg⁻¹ at a power density of 901 W kg⁻¹, successfully powering a red LED for 290 seconds. The device exhibited outstanding long-term electrochemical stability, preserving 97% of its original capacitance after 5000 consecutive charge–discharge cycles. The results demonstrate that the incorporation of conductive CoS₂ significantly improves the electrochemical performance of α-MoO₃, indicating its suitability for next-generation energy storage devices.