Direct Detection of a Phase Change in PdO/CeO₂ Supported on χ-Al₂O₃ by Means of in situ High-Temperature Measurements of XRD and FTIR

Abstract

Phase changes between PdO and Pd metal can be directly detected in PdO/CeO₂ catalysts supported on χ-Al₂O₃ by means of in situ high-temperature measurements of X-ray diffraction and FT-IR in relation to the catalytic activity for the methane oxidation of microcrystalline PdO. Reversible changes in the solid phases are observed from PdO to Pd and Pd to PdO under O₂-deficient and O₂-excess atmospheres, respectively. Nanosizes of PdO and Pd crystallites, the distorted PdO crystal structure along the (110) plane, and also a distorted Pd metal crystal structure along the (200) plane as well as the large surface area elucidate the high catalytic activity for the methane oxidation of PdO/CeO₂ catalysts prepared with an atomic ratio of Pd:Ce = 1:1.