Amorphous Tungsten Oxide/Ruthenium Oxide Composites for Electrochemical Capacitors

Abstract

Amorphous tungsten oxide/ruthenium oxide composites have been synthesized by precipitating amorphous RuO2⋅xH2ORuO2⋅xH2O on amorphous WO3⋅xH2OWO3⋅xH2O and Na0.37WO3⋅xH2ONa0.37WO3⋅xH2O under various pH conditions. The samples have been characterized by X-ray powder diffraction, elemental analysis using wavelength dispersive spectroscopy (WDS), thermogravimetric analysis, and surface area measurements. The compositions and electrochemical performance of the products are influenced by the precipitation reaction pH. The amorphous, as-prepared samples transform to rutile-type phases on heating at T⩾400°C.T⩾400°C. Amorphous samples with tungsten content as high as 50 wt % exhibit specific capacitance values of around 560 F/g, which is 200 F/g higher than that expected on the basis of rule of mixture, and thus lower the cost per unit capacitance considerably. © 2001 The Electrochemical Society. All rights reserved.