Effect of SnS2 concentrations on electrochemical properties of SnS2/RGO nanocomposites synthesized by a one-pot hydrothermal method

Abstract

Reduced graphene oxide nanosheets (RGO NSs), SnS2 nanoparticles (SnS2 NPs) and SnS2/RGO nanocomposites (SnS2/RGO NCPs) with different SnS2 concentrations (0.5, 0.7 and 2.0 mmol) were synthesized by a one-pot hydrothermal method. XRD results indicated a pure hexagonal phase of SnS2 NPs and all SnS2/RGO NCPs with space group P 6/m. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) revealed nanoplates and quantum dots morphologies of SnS2 anchored on RGO NSs of SnS2/RGO NCPs (0.5 mmol). Dispersive Raman microscopy confirmed the existence of RGO NSs in all SnS2/RGO NCPs samples. Functional groups were verified by Fourier transform infrared spectroscopy (FT-IR). SnS2 content (wt%) in each SnS2/RGO NCPs was determined by thermogravimetric analysis (TGA). Chemical surface of SnS2/RGO NCPs (0.5 mmol) was investigated by X-ray photoelectron spectroscopy (XPS). Pore-size distribution and specific surface area of SnS2 NPs and all SnS2/RGO NCPs were determined using the nitrogen adsorption-desorption isotherm. Electrochemical properties all samples were investigated by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) using the three-electrode cell system in 2.0 M KOH aqueous solution. Specific capacitance (Cs) and capacity retention of all SnS2/RGO NCPs electrodes were found to be higher than that of SnS2 NPs electrode, which might be due to the synergistic effects of RGO NSs and SnS2 NPs. Interestingly, the maximum Cs value of 273.54 F g−1 at a current density of 0.3 A g−1 with a good capacity retention of 84.25% after 1000 cycle of charge-discharge test at a current density of 5 A g−1 was obtained in SnS2/RGO NCPs (0.5 mmol).