▎ 摘　　要

Chemical doping with heterogeneous atoms is an effective method to improve the intrinsic properties of graphene. In this work, a competitive type of highly nitrogen-doped graphene (HNG) and its composites hybridized with Co3O4 nanoparticles were synthesized via simple pre-mixing followed by a hydrothermal method. The highest nitrogen content achieved was 11.7%, which endowed the graphene with superior electrochemical performance. Co3O4 nanoparticles could be obtained with an optimal size of approximately 80-100 nm and were homogenously anchored on the graphene nanosheets. Because of the synergy between the highly nitrogen-doped graphene and uniform Co3O4 nanoparticles, the HNG/Co3O4 hybrids exhibited enhanced rate capability and cycling stability, which were considerably higher than those of bare HNG and Co3O4. As the current density increased from 0.2 to 5 Ag-1, 80.6% of the specific capacitance was retained. Moreover, over 84.5% of the original specific capacitance was maintained after cycling 1000 cycles. This study has demonstrated the significance of nitrogen doping on the performance of graphene-based materials for supercapacitor electrodes. (C) 2016 Elsevier B.V. All rights reserved.