Hydrous ruthenium oxide (RuO(x)(.)nH(2)O) with average special capacitance of 105 Fg(-1) were directly prepared on titanium substrate by cyclic voltammetric (CV) deposition from an aqueous chloride solution in the -100 to 1000mV range. Voltammertric responses studied by cyclic voltammograms as well as the charging and discharging behavior examined by chronopotentiometry in 1.0 M H2SO4 demonstrated high redox reversibility and obvious pseudocapacitance characterization of RuO(x)(.)nH(2)O for application in electrochemical capacitors. X-ray diffraction spectra exhibited an amorphous structure of this hydrous oxide. The deposited oxides, consisted of mixed oxyruthenium species, with various oxidation states are demonstrated by X-ray photoelectron spectroscopy. The RuO(x)(.)nH(2)O morphologies are uniform and compact after 60 growth cycles demonstrated. (c) 2005 Elsevier B.V All rights reserved.