Enhancing redox activity and surface reactivity via hierarchical α-MoO₃ nanobelt incorporation into layered WS₂ nanosheets for high performance symmetric and asymmetric supercapacitors

Nanostructured WS2 has drawn growing interest for its low cost, non-toxic nature, and electrochemical efficiency, yet it struggles to meet the requirements for practical use, including a broad potential window, excellent rate capability, high energy and power density, and operational stability. This study aimed to develop a redox-active (WS2/α-MoO3) nanocomposite electrode, synthesized via a facile hydrothermal method, and evaluate its performance for both symmetric and asymmetric supercapacitor applications. Also, the influence of varying α-MoO3 content (0, 1, 3, 5, and 7 wt%) on the surface morphology, structural properties, and electrochemical performance of WS2 nanosheets was systematically investigated using comprehensive characterization techniques. The hierarchical 2D-1D nanocomposite structure offers multiple electrochemical benefits: (i) enhanced redox activity: contributes to greater charge storage capability by enabling multiple and reversible redox reactions during cycling, (ii) increased surface reactivity: provides more accessible electroactive sites, accelerating ion-electron interactions, and (iii) the presence of oxygen vacancies and interfacial defects: serves as active channels for ion diffusion and charge transfer, reducing internal resistance. Electrochemical measurements revealed a specific capacitance of 715 F g-1 at 0.5 A g-1, with 85% of its initial capacitance retention after 6000 charge-discharge cycles at a high current density of 12 A g-1. The WS2/α-MoO3 symmetric cell exhibited surface-controlled capacitive behavior, leading to superior rate capability. The asymmetric WS2/α-MoO3//AC supercapacitor, with a wider cell potential of 1.5 V, achieved an energy density of 37.1 W h kg-1 at a power density of 1.23 kW kg-1 along with long-term stability (82.5% retention after 6000 cycles).