Hierarchically Porous Nickel Oxide Nanosheets Grown on Nickel Foam Prepared by One-Step In Situ Anodization for High-Performance Supercapacitors

Porous NiO nanosheets are successfully grown on nickel foam substrate through an in situ anodization by using molten KOH as the electrolyte. High-purity NiO is directly obtained by this one-step method without any subsequent treatment. The obtained NiO supported on nickel foam is used as a binder-free electrode for a supercapacitor and its pseudocapacitive behavior has been investigated by cyclic voltammetry and galvanostatic charge-discharge tests in a 6M aqueous solution of KOH. Electrochemical data demonstrates that this binder-free electrode possesses ultrahigh capacitance (4.74Fcm(-2) at 4mAcm(-2)), excellent rate capability, and cycling stability. After 1000cycles, the areal capacitance value is 9.4% lower than the initial value and maintains 85.4% of the maximum capacitance value.