In situ XAFS study of highly reducible mixed oxide catalysts Ce0.9Pd0.1O2-δ and Ce0.7Yb0.2Pd0.1O2-δ

Abstract Within this paper the simultaneous local structural analysis of the highly reducible mixed oxides catalysts Ce0.9Pd0.1O2-δ and Ce0.7Yb0.2Pd0.1O2-δ is presented under reduction and oxidation conditions at elevated temperatures up to 500 °C. In situ X-ray Absorption Fine Structure characterization shows that during the reduction up to 80 °C no changes are observed in both of the exemplarily studied samples. The oxidation of the Ce1-xPdxO2-δ sample continuously introduces changes in the structure over the whole temperature range while for the Ce0.7Yb0.2Pd0.1O2-δ sample oxidation is completed already at 200 °C. The metallic palladium cluster formation in both studied samples was followed by Extended X-ray Absorption Fine Structure (EXAFS) studies. The presence of the Yb atoms affects the formation time and the Pd cluster size. It was found that during the reduction process the palladium cluster creation is initiated at higher temperatures for the Ce0.9Pd0.1O2-δ sample than for the Ce0.7Yb0.2Pd0.1O2-δ sample. The higher percentage of Pd atoms creates metallic palladium clusters in the Ce0.9Pd0.1O2-δ sample.