XPS study of Pt/Ce_xZr_1-xO₂/Si composite systems

This work describes the study of the surface reduction of ceria zirconia mixed oxides (CeZrO) as either thin films or powders, both with and without Pt present. XPS was used to measure the composition of the surface and the oxidation states of all metals contained within the material. The thin films of CeZrO showed little reactivity towards the reducing conditions used. Grazing incidence angle XRD showed the presence of Ce_0.75Zr_0.25O₂. The thin films prepared with Pt showed that surface reduction of Ce⁴⁺ occurred under reducing conditions. The size of the Pt clusters was also determined from the data. The Pt was found to always exist in the metallic state. The Zr⁴⁺ was not seen to change during all treatments. For the powder samples the Ce⁴⁺ was readily reduced to approximately 60%. Pt was found to be initially oxidised with the % of metallic Pt increasing with reduction temperature. Again no change in the Zr was observed.