Characterization of the Structure of RuO₂−IrO₂/Ti Electrodes by EXAFS

Abstract

The structure of oxide layers of the RuO2−IrO2/Ti electrode system and the thermal decomposition processes of RuCl3 and IrCl3 to form their respective oxides have been mainly analyzed by EXAFS (extended X-ray absorption fine structure) and XRD (X-ray diffraction). Upon heating of the respective chlorides in air, both chlorides convert into their respective oxides. The coordination numbers of the oxide ions around both the ruthenium and iridium ions increased with an increase in the calcination temperature and attained 6, which is the theoretical value of the standard samples of rutile RuO2 and IrO2. The changes in the coordination number with respect to the calcination temperature were accompanied by changes in the lattice constants of these oxides. This suggests that the deviation of these parameters from the standard sample is caused by the lattice defects of the oxide ions. A dependence of the radial distribution functions of EXAFS on the composition of the RuO2−IrO2/Ti electrode system showed that RuO2 forms a solid solution with IrO2 for the binary oxide electrode system.