High-performance Co3O4/CoMoO4 core/sheath heterostructure on stainless steel as a stable electrode for advanced symmetric supercapacitors

The development of core/sheath based heterostructure electrodes has gained significant attention due to synergistic effect that provide increased active sites and improved charge transport. Moreover, the sheath protects the core leading to the prolonged structural and electrochemical stability. Herein, we have synthesized Co3O4 nanoplates coated thin layer of CoMoO4 nanoparticles forming Co3O4/CoMoO4 core/sheath heterostructure on low-cost, conductive, and mechanically stable stainless steel substrate for supercapacitor application. A combined approach of successive ionic layer adsorption and reaction (SILAR) and electrodeposition wherein the number of SILAR cycles and deposition time are optimized to control the structural, morphological, and supercapacitive properties of the Co3O4/CoMoO4 heterostructure. The Co3O4/CoMoO4 heterostructure exhibited significantly enhanced supercapacitive performance compared to the bare Co3O4 and CoMoO4 electrodes when evaluated in a 1 M KOH electrolyte. Notably, it demonstrated a specific capacitance of 1187.6 F g-1 at 4 A g-1, excellent rate capability (80%) for 5-fold increase in the current density and cycling stability of 87.5%. Furthermore, Co3O4/CoMoO4//Co3O4/CoMoO4 symmetric supercapacitor is fabricated that delivered highest energy and power densities of 11.8 kW kg-1 and 71.2 Wh kg-1, respectively. Thus, the present work advances design of core/sheath based metal oxides for high performance energy storage application.