Supercapacitive performances of few-layer MoS2 on reduced graphene oxides

Reduced graphene oxide/molybdenum disulfide composites (RGO/MoS2s) with steric structures were directly synthesized via a hydrothermal approach using a redox reaction between MoO3 and thiourea. Such RGO/MoS2s were examined by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The electrochemical performances of RGO/MoS2 hybrid electrodes were then assessed by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectrometry (EIS) in 1 M Na2SO4 aqueous solutions. RGO/MoS2 hybrid materials exhibit a high specific capacitance of 243.4 F/g at 0.5 A/g, a superior cycling stability (92% retention after 2000 cycles at 1 A/g) and a distinctively high coulombic efficiency (near 100% after 2000 cycles) as well. Such excellent electrochemical behaviors could be ascribed to the steric structure of bending MoS2 nanosheets decorated on the surfaces of RGO, which favors facilitating the fast ion diffusion and the high conductivity in pseudocapacitive electrodes. Our findings suggested that the resulting morphologies and electrochemical performances of RGO/MoS2 hybrid materials could be tuned via varying steric structures of pseudocapacitive materials, which may render an alternative strategy to improve the electrochemical performance as supercapacitive electrodes.