Hydrothermal growth of MnO2/RGO/Ni(OH)2 on nickel foam with superior supercapacitor performance

Abstract

A MnO₂/reduced graphene oxide (RGO)/Ni(OH)₂ composite with arrays of mushroom-headed needle-like nanostructures on its top surface was designed and directly grown on nickel foam through a one-pot hydrothermal process without the addition of any source of extra Ni ions. Based on the redox reaction of elemental Ni and graphene oxide (GO), along with electrostatic forces between Mn ions from the solution and GO, there was good contact and strong interaction between the different components, as well as between the active materials and the Ni substrate. Hence, the as-synthesized MnO₂/RGO/Ni(OH)₂ composite can be utilized as a supercapacitor electrode with a high areal mass loading of 5.4 mg cm⁻². It exhibits superior performance: 17.8 F cm⁻² (i.e., 3296.9 F g⁻¹) at 7 mA cm⁻² (1.3 A g⁻¹), as well as a capacity retention of 90.2%, even after 5000 cycles at 20 mA cm⁻² (3.7 A g⁻¹).