A series of CuO-doped activated carbons (CDACs) were prepared by chemical deposition. The electrochemical behavior of CDACs was investigated in electrochemical capacitors based on ionic liquid 1-ethyl-3-methylimidazolium thiocyanate ([EMlm]SCN) as electrolyte. The results indicated that a diffusion-controlling, reversible redox reaction of CuO particles happened in ionic liquid and porous carbon. When the amount of CuO-doped activated carbon with a specific surface area of 2460 m(2) g(-1) reached 2%, the single electrode average specific capacitance can reach the maximal value of 210 F g(-1), about 20% higher than the one used pure activated carbon as electrode material. (C) 2009 Elsevier Ltd. All rights reserved.