RuO2/activated carbon composites as a positive electrode in an alkaline electrochemical capacitor

Hydrous ruthenium oxide was synthesized by a sol-gel method on the surface of activated carbon (AC). After heat treatment at 150°C, the RuO2/AC composite was used as a positive electrode material in an alkaline electrochemical capacitor. Several composites with different Ru contents were prepared and studied. It was found that the composite containing 30 w/% Ru had a specific capacitance of about 333 F/g at a low current density, whereas that of the pure AC was only about 241 F/g. With an increase of Ru content, the spe-cific capacitance of the electrode increased correspondingly. When the Ru content exceeded 10 w/%, the specific capacitance contributed by RuO2·xH2O was about 440 F/g. The performance of the composite under the condition of high rate discharge was as good as that of the AC electrode.