Novel synthesis of nickel oxide-copper hexacyanoferrate binary hybrid nanocomposite for high-performance supercapacitor application

Nowadays, metal hexacyanoferrate/metal oxide composites have attracted intense interest as an electrode material for supercapacitor applications due to their open framework structure, high porosity, large surface area, and redox yielding nature. In this respect, we report a novel, facile, and cost-effective chemical route for the synthesis of nickel oxide-copper hexacyanoferrate binary hybrid nanocomposite (NiO₂-CuHCF). Copper hexacyanoferrate has fascinating characteristics including redox capabilities, unique structure, cyclic stability, and open framework channels that make the transportation of alkali ions fast to achieve high supercapacitive properties. Incorporation of various metallic oxides, carbon-based materials, and metal ions can be done in CuHCF to further enhance its supercapacitive features. Nickel oxide nanostructures have attractive properties including large surface area, high porosity, good electronic conductivity, and multiple oxidation states such as Ni³⁺/Ni²⁺ that are favorable for rapid redox reactions, causing electrochemical properties to enhance. Our study, for the first time, demonstrates that as-synthesized NiO₂-CuHCF delivered superior specific capacitance of 908 Fg⁻¹ at a current density of 2 Ag⁻¹ and retained excellent rate capabilities, and outstanding cycling stability (86.5% capacity retention at 2 Ag⁻¹ after 1600 cycles) highlighting its potential use for the practical electrochemical energy storage applications.