In this paper, graphene sheets with different reduction levels have been produced through thermal reduction of graphene oxide in the temperature range of 200-900 degrees C. The effects of interlayer spacing, oxygen content, BET specific surface area and disorder degree on their specific capacitance were explored systematically. The variation of oxygen-containing groups was shown to be a main factor influencing the EDL capacitor performances of the pyrolytic graphene. The highest capacitance of 260.5 F g(-1) at a charge/discharge current density of 0.4 A g(-1) was obtained for the sample thermally reduced at about 200 degrees C. (C) 2011 Elsevier By. All rights reserved.