Effects of activation temperature on the deoxygenation, specific surface area and supercapacitor performance of graphene

This paper systematically studies the influence of temperature during KOH activation of graphene on quantities and types of oxygen-containing groups, pore structure, specific surface area, and performance of supercapacitor. The changes of the amount and types of oxygen-containing functional groups were observed with the aid of Fourier transform infrared spectroscopy, Raman and X-ray photoelectron spectroscopy. The pore structure and specific surface area were characterized by means of X-ray powder diffraction, N2 adsorption-desorption and transmission electron microscopy. Electrochemical properties were assessed by cyclic voltammetry, electrochemical impedance and galvanostatic charge-discharge. As the temperature increased, the oxygen content of activated graphene decreased, while its specific surface area increased. The specific capacitance of the activated graphene first increased and then decreased with a maximum (326 F/g) at 400 °C. When the temperature was 800 °C, the surface area of the material peaked (3269 m2/g), and the specific capacitance was 204 F/g.