The electrochemical energy storage and delivery on the electrodes composed of hydrous ruthenium oxide (RuOx.nH(2)O) or activated carbon-hydrous ruthenium oxide (AC-RuOx) 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 RuOx.nH(2)O deposited on SS meshes (RuOx/Au/SS) are found to greatly improve the poor contact between SS meshes and electrode materials. The maximum specific capacitance (C-S.RuOx) of RuOx.nH(2)O, 1580 F g(-1) (measured at 1 mV s(-1)), very close to the theoretic value, was obtained from an AC-RuOx/RuOx/Au/SS electrode with 10 wt.% sol-gel-derived RuOx.nH(2)O annealed in air at 200degreesC for 2 h. The highly electrochemical reversibility, high-power characteristics, good stability, and improved frequency response of this AC-RuOx/RuOx/Au/SS electrode demonstrate its promising application potential in supercapacitors. The ultrahigh specific capacitance of RuOx.nH(2)O probably results from the uniform size distribution of RuOx.nH(2)O nanoparticles, ranged from 1.5 to 3 nm which is clearly observed from the high-resolution transmission electron microscopy (HRTEM). (C) 2004 Elsevier Ltd. All rights reserved.