Nitrogen-doped porous carbons are very simply prepared by direct pyrolysis of a nitrogen-containing organic salt, the tetrasodium salt of ethylenediamine tetraacetic acid for example, at 600-900 degrees C in an inert atmosphere without activation. The porosity and surface chemistry of the carbon depend strongly on the pyrolysis temperature. The surface area and pore volume increase with the pyrolysis temperature, and vary from 408 to 1171 m(2) g(-1) and 0.209 to 0.709 cm(3) g(-1), respectively. While the nitrogen content decreases from 8.59 at% for pyrolysis at 600 degrees C to 1.02 at% at 900 degrees C. The unique microstructure and nitrogen functionalities enable the carbon to exhibit a capacitance of 245 Fg(-1) in a 6 mol L-1 KOH aqueous electrolytes, which is attributed to the contributions of double layer capacitance and pseudo-capacitance, with an excellent rate capability (188 F g(-1) remained at 20A g(-1)) and cycle durability. (C) 2013 Elsevier Ltd. All rights reserved.