Nitrogen doped graphene (NDG) has been synthesized using a microwave-assisted hydrothermal (MHT) method within only several minute. In the method, homemade graphene oxide was reduced using ethylene glycol (EG) to obtain the graphene while ammonia liquid was used as the nitrogen source. However, it was found that the reduction and doping simultaneously occurred and the addition of ammonia further enhanced the reduction. The reduction and doping were examined through various analysis and the mechanisms were proposed. The effects of the hydrothermal temperature and time on the reduction and doping were discussed. It was also shown that the doping leads to enhanced specific capacitance by as much as 54%, a high specific energy density of 42.8 Wh kg(-1) at a power density of 4330 W kg(-1), and excellent long term stability up to 98% retention after 1000 cycles at wide working voltage of 1.6V in 2 M H2SO4. (c) 2015 Elsevier B.V. All rights reserved.