Abstract
The electrochemical energy storage and delivery on the electrodes composed of hydrous ruthenium oxide (RuO x ·nH 2 O) or activated carbon-hydrous ruthenium oxide (AC-RuO x ) composites are found to strongly depend on the substrate employed. The contact resistance at the active material-graphite interface is much lower than that at the active material-stainless steel (SS) mesh interface. Thin films of gold plus RuO x ·nH 2 O deposited on SS meshes (RuO x /Au/SS) are found to greatly improve the poor contact between SS meshes and electrode materials. The maximum specific capacitance (C S,RuOx ) of RuO x ·nH 2 O, 1580Fg -1 (measured at 1mVs -1 ), very close to the theoretic value, was obtained from an AC-RuO x /RuO x /Au/SS electrode with 10wt.% sol-gel-derived RuO x ·nH 2 O annealed in air at 200°C for 2h. The highly electrochemical reversibility, high-power characteristics, good stability, and improved frequency response of this AC-RuO x /RuO x /Au/SS electrode demonstrate its promising application potential in supercapacitors. The ultrahigh specific capacitance of RuO x ·nH 2 O probably results from the uniform size distribution of RuO x ·nH 2 O nanoparticles, ranged from 1.5 to 3nm which is clearly observed from the high-resolution transmission electron microscopy (HRTEM). © 2004 Elsevier Ltd. All rights reserved.