Effect of Nitrogen Doping on the Migration of the Carbon Adatom and Monovacancy in Graphene

Nitrogen-doped graphene (N-graphene) has important implications in graphene-based devices and catalysts. Nitrogen incorporation into graphene via postsynthetic treatment is likely to produce a non-negligible amount of defects and bond disorders, and the resulting nitrogen content is usually dominated by graphitic N and pyridinic N. To understand the kinetic stability of doped N and the effect of doped N on the self-healing of monovacancy in graphene, we have performed density functional theory calculations to study the adsorption and migration of an adsorbed C atom on undoped and N-doped graphene with and without a monovacancy (MV). The effects of N doping and hydrogenation on the migration of a MV in graphene are also studied. Our results suggest that the graphitic N doped in the vicinity of MV is kinetically unstable, and it could be transformed into a pyridinic N due to the migration of MV when N-graphene is through high-temperature annealing. The presence of a C adatom would easily repair the vacancy of defective graphene with MV and either restore perfect graphene or form a Stone-Wales defect. Similar repairing processes were also found in the case of a C adatom near MV with a pyridinic N.