Binary mixed metal oxide sphere-like structures for hybrid supercapacitor electrode with improved electrochemical properties

The facile fabrication of stable and highly efficient metal oxide-based electrode materials by regulating the electroactive sites is crucial for supercapacitor applications. In this work, a two-step synthesis strategy comprising hydrothermal and heat treatment was employed to prepare the NiWO₄/WO₃ (NW/W-O) as electrode materials for supercapacitors. Moreover, the heat treatment temperature influences and alters the physicochemical and electrochemical properties of the obtained NW/W-O products. The material prepared at 500 °C (NW/W-O(A)) unveils low crystallinity, small particle size, and a large surface area with a narrow porous feature than the material obtained at 600 °C (NW/W-O(B)). Thus, the NW/W-O(A) electrode could be anticipated for effective charge transfer and better capacitive behavior. Notably, the NW/W-O(A) material exhibited a superior specific capacitance of 825 F g⁻¹ than NW/W-O(B) with 536 F g⁻¹ at a current density of 1 A g⁻¹. Further, the NW/W-O(A) displayed a higher rate capability of 60% (@ 20 A g⁻¹) than that of NW/W-O(B) (49%). The designed hybrid supercapacitor (NW/W-O(A)//AC) showed a high specific capacitance of 108 F g⁻¹ and energy density of 33.77 Wh kg⁻¹ at a power density of 896.39 W kg⁻¹ with long-term cyclic retention of only <12% deterioration over 10,000 cycles. Hence, this work demonstrates that the influence of heat treatment temperature is a crucial parameter in tailoring electrode materials with promising energy storage capability.