关键词: 石墨烯, 赝电容, 超级电容器, 表面官能团, 热还原

Abstract: In this paper, thermal-reduced graphene oxide (T-RGO) materials are synthesized by modified Hummer’s method, followed by thermal reduction under argon atmosphere at different temperatures. Electrochemical investigations show that, for T-RGO electrodes, good electrical conductivity is necessary and the surface functional groups play more significant role than the specific surface area in determining the electrochemical capacitance. The T-RGO obtained at 900 °C (T-RGO900) with a relatively high Brunauer-Emmett-Teller (BET) surface area (314 m²·g^-1) and a high electrical conductivity (2421 S·m^-1) shows a low specific capacitance of 56 F·g^-1. In comparison, the T-RGO obtained at 300 °C (T-RGO300) with a relatively low BET surface area (18.8 m²·g^-1) and an electrical conductivity (574 S·m^-1) provides the largest specific capacitance of 281 F·g^-1. The large specific capacitance of T-RGO300 results from the simultaneous contributions of the electrochemical double-layer capacitance and the pseudo-capacitance obtained from the oxygenated groups on the T-RGO surfaces. Therefore, it probably gives a new insight for designing and synthesizing graphene-based electrode materials for supercapacitors and other energy-storage devices.

Key words: graphene, pseudo-capacitance, supercapacitor, surface functional groups, thermal reduction