Thermal behaviour during initial stages of graphene oxidation: Implications for reaction kinetics and mechanisms

Atomic level understanding of graphene oxidation behaviour is presently far from complete. During large scale preparation of graphene from graphene oxide (GO), persistent presence of up to 8% residual oxygen is an issue of great concern. Such incomplete reduction is attributed to the presence of highly stable carbonyl and ether groups. Here we present a new approach for limiting the formation and behavior of these functional groups. We report high temperature molecular dynamics simulations on the oxidation process of pristine (Pr) and monovacancy (MV) graphene with O2 with specific focus on the initial reaction period. An abnormal thermal behaviour was observed in the onset times of oxidation reactions; significant differences were detected in the nucleation and growth mechanisms and reaction kinetics. Overall reaction kinetics was significantly slower in the thermal region (Pr: 4350-4450 K; MV: 4300-4450 K). By identifying this region experimentally or theoretically, a narrow window of minimal carbonyl group formation and residual oxygen could be created leading to a major breakthrough in the field.