In this study, we present a simple but efficient template carbonization method to prepare nitrogen-doped nanoporous carbon material, in which phenidone acts as carbon/nitrogen sources and Mg(OH)(2) as hard template. The results indicate that the carbon-1:1 sample is highly disordered with large BET surface area of 1513 m(2) g(-1), high pore volume of 2.2 cm(3) g(-1) and nitrogen content of 3.78%. As a result, it exhibits decent electrochemical behaviors, whose specific capacitance reaches up to 202.0 F g(-1) when measured at I A g(-1) in a three-electrode system. Moreover, azodicarbonamide has been introduced in the process of carbonization to further tailor the porosity of nanoporous carbon, named as the carbon-1:1:1 sample. In consequence, its BET surface area has decreased to be 1261 m(2) g(-1) but the pore volume increased up to 2.8 cm(3) g(-1), together with the large enhancement of nitrogen content up to 7.05%. Besides, it thus delivers a higher specific capacitance of 281.0 F g(-1) at 1 A g(-1), mostly due to the incremental content of nitrogen species. The proposed Mg(OH)(2)-assisted template carbonization method has provided an intriguing synthesis approach for N-doped nanoporous carbons, especially the nitrogen improvement simply by the addition of azodicarbonamide. (C) 2015 Elsevier Ltd. All rights reserved.