Graphene nanosheets-tungsten oxides composite for supercapacitor electrode

Graphene nanosheets-tungsten oxides (tungsten oxide/tungsten oxide hydrate mixture) (GNS-W) composite was successfully synthesized using a facile approach. WO3/WO3·H2O mixtures were deposited on the graphene nanosheets (GNS) to form the GNS-W composite. The GNS-W composite was characterized by X-ray diffraction (XRD), Raman spectrum, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The as-prepared GNS-W composite was directly fabricated into a supercapacitor electrode for potential energy storage application, and electrochemically tested by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The GNS-W composite electrode exhibits a better electrochemical performance than that of the WO3/WO3·H2O mixtures electrode. A high specific capacitance of about 143.6 F g−1 at a current density of 0.1 A g−1 for the GNS-W composite delivers significant improvement than that for the WO3/WO3·H2O mixtures and GNS electrodes. The impedance studies also suggest that the GNS-W composite electrode shows the lower resistance and high conductivity due to the good interaction between the graphene nanosheets and the WO3/WO3·H2O mixtures. The good electrochemical performance for the GNS-W composite may be attributed to the interaction between the WO3/WO3·H2O mixtures and the edges of graphene nanosheets, which increases the ion diffusion rate as well as the conductivity.