Composite electrodes for surpercapacitors were fabricated by depositing polyaniline (PAn) on the surface of activated carbon powders (ACP) by using the electrochemical method. Their capacitance values were measured in the 1 M H2SO4 aqueous electrolytes containing SiO2, which showed the conductivity values of 2.6 x 10(-1), 2.3 x 10(-1), and 1.5 x 10(-1) S/cm for their liquid, gel, and solid-like gel states, respectively, according to the content Of SiO2. The Pt/ACP/PAn electrodes showed a specific capacitance value of 270 F/g in the 1 M H2SO4 solid-like electrolyte, which value was larger than the capacitances of 144 and 209 F/g for the Pt/ACP and the Pt/PAn, respectively. This result suggests that the capacitance performance of the ACP can be improved by compositing with PAn, and the 1 M H2SO4 solid-like electrolyte is suitable for the use in the supercapacitor. (C) 2004 Elsevier Ltd. All rights reserved.