▎ 摘　　要

Controlled oxidation of graphene is extremely important for nanopatterning and chemical functionalization. It is generally assumed in experiments that the oxidizing agent in the liquid-phase oxidation first attacks the defective sites in carbon lattices. To explore how the oxidation in the graphene sheet first begins, we have investigated the oxidization process with the structural defect using the density functional theory. Ten reaction pathways in the frame of the transition state theory are considered. We find that the most preferential reaction locus is located at the center of defect. It has also been observed that the preexistence of hydroxyl functional group on the graphene surface substantially decrease energy barrier for oxidization. Such facilitation of oxidation due to hydroxyl can explain how the oxidation process continues after its first oxidation around defects. The uneven redistributions of electron density caused both by defect and by the hydroxyl functional group account for the mechanism of the oxidization process on graphene sheet. Our calculation fully verifies the experimental assumption and is consistent with the recent experimental observations. (C) 2016 Elsevier B.V. All rights reserved.