Solvothermal synthesis of graphene nanosheets as the electrode materials for supercapacitors

Graphene nanosheets (GNs) were prepared by one-pot solvothermal reduction in ethanol at different temperatures as supercapacitor electrode materials. The results of X-ray diffraction showed that the layer-to-layer distance of GNs decreased with the increase of temperature. Compared to graphite oxide (GO), these decreased values indicated that the enhanced temperature promoted the deoxidization of GO to GNs. Raman spectra showed that GNs exhibited numerous smaller disordered graphitic domains at elevated temperature. Based on the analysis results of the X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy, the higher solvothermal temperature was beneficial to remove more oxygen-containing groups of GO and obtain better quality GNs. The electrochemical performances of GNs had been studied by cyclic voltammetry and galvanostatic charge-discharge cycling techniques. The results revealed that the capacitive values increased with increasing temperature and the GNs at 493 K could provide a high specific capacitance of 186 F g⁻¹ at a current density of 0.1 A g⁻¹ in the 6 M KOH solution.