One-pot solvothermal synthesis of flower-like copper sulfide/reduced graphene oxide composite superstructures as high-performance supercapacitor electrode materials

Abstract

A series of CuS/RGO composite superstructures with different RGO contents as well as contrastive bare CuS superstructure were one-pot solvothermally synthesized. The structure, morphology, chemical composition and crystalline phase of these products were systematically studied and characterized by a number of modern techniques like field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectra, X-ray diffraction, atomic absorption spectroscopy and Raman characterizations. Their electrochemical performances were also carefully examined by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy tests. It was found that all the CuS/RGO superstructures featured unique hierarchically flower-like architecture. When used as supercapacitor electrode material, CuS/RGO-4 superstructure with the RGO content of 31.7 wt% delivered a maximum specific capacitance of 368.3 F g−1 at the current density of 1 A g−1, which was much higher than that of the other CuS-containing superstructures synthesized in this work and lots of CuS-based electrode materials reported recently. It is assumed that the unique morphology, improved conductivity and favorable synergetic effect between the two constituents of CuS and RGO are responsible for the enhanced supercapacitive behaviors of CuS/RGO-4 superstructure, which not only expedite the charge transport but also elevate the electrolyte diffusion. Additionally, CuS/RGO-4 superstructure electrode gave satisfactory long-term stability and durability and 88.4% of the initial capacitance was maintained after repetitive charge/discharge for 1000 cycles at the current density of 3 A g−1, exhibiting promising applicability in energy-storage devices.