▎ 摘　　要

Despite the extraordinary impermeability of graphene, graphene fails to prevent oxidation of Cu surfaces under ambient conditions. Cu surfaces under a graphene layer oxidized faster than a bare Cu surfaces. The mechanism underlying the accelerated oxidation of Cu surfaces under graphene has remained unclear and has limited the application of graphene as an oxidation barrier for various metals. Here, we elucidated the mechanism underlying oxidation of a Cu surface under graphene layers. The diffusivity of Cu cation vacancies through the oxide layer, which is the rate-determining step of Cu oxidation, was found to be affected by a graphene layer via changes in the chemical composition of the oxide. Based on our findings, we proposed methods for improving the oxidative barrier properties of graphene. This work could provide guidance on the use of graphene to prevent oxidation of various metals. (C) 2017 Published by Elsevier Ltd.