Vertically oriented Ni3S2/RGO/Ni3S2 nanosheets on Ni foam for superior supercapacitors

Abstract

A unique sandwich structure of Ni₃S₂/RGO/Ni₃S₂ consisting of Ni₃S₂ nanosheets was designed and constructed on nickel foam (NF) by a one-step hydrothermal process. The lower Ni₃S₂ layer was converted in situ from the Ni foam substrate, while the upper Ni₃S₂ layer with vertical nanosheets resulted from Ni²⁺ ions in the solution. This Ni₃S₂/RGO/Ni₃S₂/NF nanocomposite was directly utilized as a supercapacitor electrode, which possessed a high areal mass loading of 5.2 mg cm⁻², and superior performance: a specific capacitance of up to 16.82 F cm⁻² (i.e., 3234.62 F g⁻¹) at a current density of 20 mA cm⁻² (3.85 A g⁻¹) and 90% retention of the initial capacitance after 1000 cycles at the high rate of 100 mA cm⁻² (19.23 A g⁻¹).