Stabilization of RuO2 by IrO2 for anodic oxygen evolution in acid media

Anodic evolution of oxygen on mixed oxides RuxIr1−xO2 has been investigated for x=0,0.3,0.5,0.8 and 1 using electrochemical as well as surface physical techniques. In terms of Tafel slope and corrosion rate the electrochemical behaviour of the mixed oxide is mainly determined by the iridium component for x <0.5. XPS results show that there is no change in surface composition during O2 evolution. Valence band spectra and cyclic voltammetry results suggest that band mixing occurs, giving rise to a shift of oxidation potentials. While the activity of the RuO2 component in the mixed oxide is lost the stability of the slightly activated IrO2 component is maintained. A model for the stabilization effect is proposed.