Effects of substrates on the capacitive performance of RuO x· nH 2O and activated carbon–RuO x electrodes for supercapacitors

Abstract

The electrochemical energy storage and delivery on the electrodes composed of hydrous ruthenium oxide (RuO x · nH 2O) 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 2O 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 ,RuO x ) of RuO x · nH 2O, 1580 F g −1 (measured at 1 mV s −1), very close to the theoretic value, was obtained from an AC–RuO x /RuO x /Au/SS electrode with 10 wt.% sol–gel-derived RuO x · nH 2O annealed in air at 200 °C for 2 h. 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 2O probably results from the uniform size distribution of RuO x · nH 2O nanoparticles, ranged from 1.5 to 3 nm which is clearly observed from the high-resolution transmission electron microscopy (HRTEM).