Evaluation of the redox behavior of hydrous ruthenium oxides: Effect of temperature and acid concentration on the electrochemical behavior of layered ruthenium oxide

Abstract

The effect of the H2SO4 concentration and cell temperature towards the pseudocapacitive behavior of layered ruthenic acid hydrate, H0.2RuO2.1 · H2O. was examined. The increase in H2SO4 concentration resulted in a drastic decrease in the redox pair observed at 0.65 V vs. RHE, while the increase in cell temperature had little effect on this redox pair. The redox pair centered at ∼ 0.85 V vs. RHE was less dependent on the H2SO4 concentration and the charge associated with this peak increased with increasing cell temperature. It is suggested that the redox peak observed at ∼ 0.65 V vs. RHE is related to the adsorption of SO42- ions on the outer surface of the microsized particles. The redox pair observed at ∼ 0.85 V vs. RHE is attributed to the penetration of protons or hydrated protons. The effect of cell temperature was negligible for nanoparticulate RuO2·xH 2O., which indicates the difference in the charge storage mechanism of layered H0.2RuO2.1·nH2O and nanoparticulate RuO2·xH2O.