A facile one-step route to RGO/Ni₃S₂ for high-performance supercapacitors

Graphical abstract: - Highlights: • A uniform 3D nest-like nanostructure of RGO/Ni₃S₂ nanocomposite on Ni foam, in-situ synthesized using a simple, green one-pot hydrothermal approach, exhibits superior capacitive performance (7440 mF cm⁻² at 10 mA cm⁻², i.e., 2188.8 F g⁻¹ at 2.9 A g⁻¹ and 1016 F g⁻¹ at 29.0 A g⁻¹).Highlights. • RGO/Ni₃S₂/NF composite was in-situ synthesized through a one-step hydrothermal process. • No other reagent except Ni foam, GO and S powder was added. • RGO/Ni₃S₂, RGO/Ni(OH)₂, and RGO/Ni₃S₂/Ni(OH)₂ can be controllably synthesized. • As-prepared RGO/Ni₃S₂/NF nanocomposite exhibits high capability and cyclability. - Abstract: A facile one-step solution-phase route to RGO/Ni₃S₂ on nickel foam (RGO/Ni₃S₂/NF) was presented. The RGO/Ni₃S₂/NF (RNS) nanocomposites were hydrothermal-assisted synthesized, in which nickel foam acted as an auxiliary reductant of GO and S, a Ni source of Ni₃S₂, and a substrate for composite film. RGO/Ni₃S₂/NF composites were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscope (FESEM), and transmission electron microscopy (TEM). The electrochemical performances of the supercapacitor with as-synthesized RGO/Ni₃S₂/NF (RNS) electrodes are evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectrometry (EIS) in 2 M KOH aqueous solution. It is found that the RGO/Ni₃S₂/NF electrode exhibits superior supercapacitor performance (7440 mF cm⁻² at 10 mA cm⁻², i.e., 2188.8 F g⁻¹ at 2.9 A g⁻¹), compared with the Ni₃S₂/NF electrode (4360 mF cm⁻² at 10 mA cm⁻²) and the RGO/Ni(OH)₂/NF electrode (3400 mF cm⁻² at 10 mA cm⁻²) prepared under identical conditions. Both the temperature and sulfur content play important roles in the controlled synthesis of RNS and its electrochemical performance