XPS study of the state of iridium, platinum, titanium and oxygen in thermally formed IrO2+TiO2+PtOX films

Electrodes of nominal composition Ir0.3Ti(0.7−x)PtxO2 (x=0; 0.4 and 0.7) have been prepared by thermal decomposition of mixtures of the chloride precursors. H2PtCl6 was used as Pt-precursor. A systematic study of the chemical composition and oxidation states of the elements of these electrodes was performed by XPS. XPS analysis showed that the surface of the PtOx-containing coatings are Pt enriched. Additionally, XPS revealed that the Ir signals are almost absent from the spectra of PtOx-containing electrodes, while the Ti signal is completely absent. On the basis of the XPS results it is possible to propose a model of the surface structure of these electrodes: the grains, composed almost exclusively of Ir+Pt, are Pt enriched and distributed in a matrix, which although having Ti in its composition, besides Ir and Pt, is also Pt enriched. This finding corroborates the electrochemical behaviour of these electrodes, which is characteristic of polycrystalline Pt.