Oxidation of graphene with variable defects: alternately symmetrical escape and self-restructuring of carbon rings

Variable defects such as vacancies and grain boundaries are unavoidable in the synthesis of graphene, but play a central role in the activation of oxidation. Here, we apply reactive molecular dynamics simulations to reveal the underpinning mechanisms of oxidation in graphene with or without defects at the atomic scale. There exist four oxidation modes generating CO2 or CO in different stages, beginning from a single-atom vacancy, and proceeding until the ordered structure broken down into carbon oxide chains. The oxidation process of the graphene sheets experiences four typical stages, in which alternately symmetrical escape phenomenon is observed. Importantly, disordered rings can self-restructure during the oxidation of grain boundaries. Of all defects, the oxidation of vacancy has the lowest energy barrier and is therefore the easiest point of nucleation. This study demonstrates the crucial role of defects in determining the oxidation kinetics, and provides theoretical guidance for the oxidation prevention of graphene and the production of functionalized graphene.