Nickel foam supported biochar doped Ni–Mo bimetallic oxide for supercapacitor application†

As novel energy storage devices that have garnered significant attention, supercapacitors offer merits including long cycle life, high power density, ease of fabrication, and rapid charge/discharge rates. The core component of supercapacitors is an electrode material. Carbon materials are the most widely used in supercapacitors. However, their intrinsic charge storage mechanism results in relatively low capacitance performance, which falls short of the requirements for high-performance electrode materials. In this study, rice husks were converted into biochar. The porous biochar produced exhibits characteristics such as a well-developed porous structure, high specific surface area, tunable architecture, and low cost. Polyoxometalates exhibit excellent redox properties and high stability, offering advantages such as acting as electron reservoirs or electron sponges. C-MoO₃-NiO₂/NF was synthesized on nickel foam (NF) by using polyoxometalate (NH₄)₄[Ni(II)Mo₆O₂₄H₆]·5H₂O as a precursor, doping with rice husk biochar and utilizing KOH for porosity development. The supercapacitor test results indicate that the C-MoO₃-NiO₂/NF electrode material exhibits a charge–discharge time reaching 374.4 s and a specific capacitance of 180.77 F g⁻¹ at a current density of 1 A g⁻¹ in 6 mol L⁻¹ KOH solution. After 1000 cycles of charge–discharge testing, the capacitance retention rate was still 75%. This indicates that the electrode material is an excellent supercapacitor material, laying a foundation for the development of novel supercapacitor materials.