Insight into the capacitive properties of reduced graphene oxide.

Graphene-based materials have been widely used as electrode materials of supercapacitors. However, the intrinsic properties related to the capacitance of graphene-based materials essentially need to be clarified. In this work, we have prepared reduced graphene oxide (RGO) through a simple chemical reduction strategy by using hydrazine hydrate as the reducing reagent. The different reduction levels of graphene sheets were successfully realized by controlling the chemical reduction time, and the surface state and density of the functional group were precisely adjusted. We investigated the electrochemical performance of the as-prepared RGO electrode materials. A time dependence of the specific capacitance for the as-prepared RGO electrode was observed. Graphene oxide reduced by hydrazine hydrate at 95 °C for 60 min exhibited the highest weight specific capacitance. The RGO samples were systematically characterized with Fourier transform infrared (FTIR) spectra, X-ray photoelectron spectroscopy (XPS), and Raman measurements. We conclude that the oxygen-containing groups, electrical conductivity, density of defects, and carbon electronic state play substantial roles in deciding the specific capacitance of reduced graphene oxide.