Formation of Intercalation Path for Oxygen Through Imperfections in Graphene on Metal Substrate: A Density Functional Theory Study

In this work, we study a basic mechanism for oxygen intercalation through defect sites due to possible imperfections, namely edges and grain boundaries, in graphene. From first-principles density functional theory calculations, graphene edge sites were found to be vulnerable to attack by oxygen, resulting in cleavage of the C-C ??-bond and buckling of the sp2-bonded planar carbon sheet. This process weakens the interaction between graphene and underlying metal surface while creating an inflow path for external oxidants. The inevitable presence of graphene grain boundaries not only builds the channel in which intercalants move, but also considerably reduces the migration energy of atomic oxygen passing directly through the graphene sheet, thereby compromising the ability of graphene to protect the underlying metal.