Cyclic voltammetric deposition of hydrous ruthenium oxide for electrochemical capacitors: Effects of codepositing iridium oxide

Abstract

The electrochemical and textural characteristics of various hydrous ruthenium-iridium oxides (denoted as (Ru+Ir)Ox·nH2O) grown by cyclic voltammetry (CV) were systematically studied for the application of electrochemical (EC) capacitors. The faradaic pseudocapacitance of (Ru+Ir)Ox·nH2O reached the maximum when the depositing solution contained 5 mM RuCl3·xH2O and 1 mM IrCl3·xH2O. The linear dependence of Ccp on Cq* measured respectively by chronopotentiometry (CP) and CV at various (Ru+Ir)Ox·nH2O deposits was found to be independent of the compositions of oxides. The intercalation of IrOx·nH2O within the RuOx·nH2O matrix promoted the utilization of electroactive oxyruthenium species while the presence of IrCl3·xH2O depressed the rate of (Ru+Ir)Ox·nH2O deposition. These effects were further supported by the textural results of these binary hydrous oxides examined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).