▎ 摘　　要

In most of the N-doped graphene (N-graphene) which attracts strong attention in the context of precious-metal free catalysts and nanoelectronics, the oxygen content is generally higher than or at least comparable to the nitrogen content. In order to understand the effect of oxygen-containing chemical groups (OmHn) on N doping in defective graphene sheets, we perform density functional theory calculations to study the interplay of oxidized monovacancy (MV) and the nitrogen doping, motivated by the fact that MV is more frequently observed and more chemically active than divacancy and Stone-Wales defect. We determine the phase diagrams of undoped and nitrogen-doped oxidized MVs as a function of temperature and partial pressure of O-2 and H-2 gases. The modification of the electronic structure of MV by oxidation and N doping is studied. Our results show that the ether group (-O- in plane) is a common component in stable configurations of oxidized MVs. Most of the stable configurations of oxidized MVs do not induce any carriers. The stabilization of pyridinic N, pyridinium-like N, and graphitic N at MV depends on the oxidation degree of MV. Our results also suggest that pyridinic N and pyridinium-like N at clean MV do not facilitate the oxygen-reduction reaction.