Synthesis of NiS–Graphene Nanocomposites and its Electrochemical Performance for Supercapacitors

The aim of this work is to synthesize nickel sulfide–graphene (NiS/G) nanocomposites with different compositions and to analyze the structural and electrochemical capacity and compatibility for their application as supercapacitor material with enhanced charge storage capacity and reduced impedance. NiS nanoparticles (NPs) loaded on graphene were synthesized at various concentrations of graphene by a simple hydrothermal route from nickel sulphate and graphene oxide as precursors in the presence of PVP as surfactant and thioacetamide (TAA) as sulfur source. The composites structural, morphological and physical properties were analyzed by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS) and Fourier Transform-infrared (FT-IR) analysis. SEM measurements showed the presence of surface attachment of the NiS NPs onto the graphene sheets. To assess the properties of the nanocomposites for their applicability in supercapacitors, electrochemical analysis was carried out in 6[Formula: see text]M KOH electrolyte. Three different samples with different graphene contents — GNiS-10 with 10 wt.%, GNiS-20 with 20 wt.% and GNiS-40 with 40 wt.% were prepared. The specific capacitances obtained for the nanocomposites were calculated to be 84.33[Formula: see text]F/g, 129.66[Formula: see text]F/g, 187.53[Formula: see text]F/g at 10[Formula: see text]mV/s scan rate, respectively. The EIS data showed that the loading of NiS NPs on graphene caused the reduction in impedance at high frequency and has a long cycle life (over 1000 cycles).