Superior Stability of Heterostructure Electrode Composed of Co₃O₄ Nanospheres and WO_3−x Nanorods in Hybrid Aqueous Supercapacitors

The development of the battery-type electrode for the hybrid supercapacitor is very challenging owing to poor cycle stability. To overcome this problem, heterostructures would be an excellent alternative attributed to the synergetic effect of different materials physical properties, including electrical conductivity, mechanical flexibility, and so forth. Furthermore, heterostructures also offer significant redox reactions on account of more active sites, enhanced charge transfers kinetics via extra electron carriers, and ion diffusion rates, along with improved cyclic stability. Herein, we prepared heterostructures of Co₃O₄ nanospheres and WO_3−x nanorods via a single-step wet chemical method at a reaction time of 1 h (CoW1) and 6 h (CoW2). The electrochemical investigations reveal improved specific capacitance of CoW1 (157 F g⁻¹) than CoW2 (188 F g⁻¹) at 0.3 A g⁻¹. Furthermore, an aqueous hybrid supercapacitor (AHS) shows the specific capacitance of 38 F g⁻¹ at 1 A g⁻¹. Notably, it exhibits a remarkable specific capacity retention of 93% up to 10 000 cycles at 100 mV s⁻¹. Thus, CoW2 have great potential of electrode materials for the next-generation energy storage devices.