▎ 摘　　要

To understand the reversible oxidation of graphene in a recent experiment, a density-functional theory study is performed. The adsorption energy of isolated oxygen atom on graphene is 2.3 eV, indicating a strong interaction between them. However, the migration barrier of oxygen atoms on graphene is only 0.8 eV and oxygen diffusion is still possible. Provided with this possibility, we find that, although a single oxygen atom is very difficult to desorb, cooperative desorption of two oxygen atoms is feasible.