▎ 摘　　要

A novel strategy for fabricating nitrogen doped graphene sheets has been developed using graphite oxide as the carbon source and urea as the nitrogen source via hydrothermal approach. This method allows us to obtain high doping level of nitrogen in graphene. The doped nitrogen mainly exists as pyridinic and pyrrolic N bonding configurations. Subsequent thermal annealing will transfer the pyrrolic N to graphitic N significantly. Electrochemical results demonstrate that larger amount of graphitic nitrogen configuration may play an active role in the excellent electrocatalytic activity toward oxygen reduction reaction (ORR) in alkaline electrolyte. (c) 2012 Elsevier B.V. All rights reserved.