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 center dot 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 center dot 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 center dot 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 center dot H2O mixtures. The good electrochemical performance for the GNS-W composite may be attributed to the interaction between the WO3/WO3 center dot H2O mixtures and the edges of graphene nanosheets, which increases the ion diffusion rate as well as the conductivity. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.