A mechanistic study of the influence of graphene curvature on the rate of high-temperature oxidation by molecular oxygen

Kinetic Monte-Carlo (KMC) simulations of the evolution of a graphene sheet in combustion-like environments were performed using a set of newly established elementary reactions of graphene-edge oxidation by O-2. The KMC results revealed two principal pathways for an oxyradical site: oxidation and regeneration of an aromatic radical site. The two pathways compete for oxyradicals, but exclusion of the regeneration pathway does not significantly affect the oxidation rate. Examination of the morphology of the evolving graphene edges indicated that the addition of O-2 promotes the formation of five-member rings embedded in the graphene. The overall oxidation rate of the graphene was computed to be time dependent, with reactivity decreasing over time as the ratio of reactive edge sites decreases relative to the number of basal-plane carbon atoms. At the same time, the oxidation rate was found to be higher for graphene with a higher initial curvature. Both results are in accord with experimental observations. Analysis showed that distinct aspects of graphene-edge morphology are responsible for curvature either raising or reducing the oxidative reactivity of the graphene edge. (C) 2016 Elsevier Ltd. All rights reserved.