▎ 摘　　要

The variation of oxygen functional groups (OFGs) is extremely complicated during the thermal treatment of graphene oxide (GO). Selectively improving the content of electrochemically active OFGs through multi-step thermal treatment is a promising strategy to enhance the charge storage capability of graphene-based super-capacitor electrodes. In this work, a two-step thermal treatment method was used to produce reduced graphene oxide (RGO) with selectively increasing the content of electrochemically active quinone-type carbonyl groups ((CO)-O-=). The first step is thermal reduction at 500 degrees C in Ar atmosphere, during which GO is exfoliated into separated sheets with porous structure and larger surface area; the second step is air oxidation at 400 degrees C, which facilitates the selective formation of quinone-type (CO)-O-= groups and enhances the mesoporous fraction. Due to the pseudocapacitive behavior of quinone-type (CO)-O-= groups and low ion diffusion resistance, the electrode prepared by RGO exhibits a high specific capacitance of 303 F g(-1) at 0.2 A g(-1) with excellent rate capability (202 F g(-1) at 10 A g(-1)) and notable cycling performance (similar to 116% capacitance retention after 1500 cycling at 1 A g(-1)). The present work proposed a facile and environmentally friendly two-step thermal treatment strategy in effectively controlling the surface property and microstructure of graphene materials, which has significant implications for mass producing graphene materials for supercapacitor electrodes.