Ruthenium oxide impregnated carbon pseudocapacitors

RuO2-impregnated carbon electrodes for an electrochemical capacitor were prepared by the direct impregnation of RuO2 on carbon with the alkaline neutralization in the RuCl3 aqueous solution, and have a high specific capacitance (180 Fg(-1) for 11.0 wt% RuO2/C). RuO2 particles on the carbon are 2 or 3 nm in diameter, and their structure was amorphous even after annealing at 573 K. The specific pseudocapacitances per RuO2 of the 1.45, 5.03 and 11.0 wt% RuO2-impregnated carbon electrodes were 1079, 1055 and 785 Fg(-1) RuO2, respectively. They were twice and more as high as calculated value on the basis of a model of hydrogen adsorption on the surface ruthenium and oxygen. This suggests that hydrogen not only adsorbs on the surface but also intercalates into the inner lattice sites of ruthenium and oxygen due to the ultra-fine and amorphous structure of RuO2 particles on the carbon.