Porous carbons with large meso/macropore surface areas were prepared by the colloidal-crystal-templating technique. The porous carbons exibited extremely high specific electrochemical double layer (EDL) capacitance of 200−350 F g-1 in an aqueous electrolyte (1 M H2SO4). The pore structure dependence of the capacitance was studied mainly by means of cyclic voltammetry and is discussed in detail. From the sweep rate dependence of the series resistance and capacitance, it was found that the ion-penetration depth at the porous electrode surface was finite and decreased with an increasing sweep rate. Peaks around the point of zero charge, which were observed in addition to typical rectangular voltammograms, were explained well by the potential drop in pores. The surface area dependence of the capacitance revealed that the contribution of the meso/macropore surface is as great as that of the plane electrodes and that only the part of the micropore surface adjacent to the opening mouths is effective.

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