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

Phase changes between PdO and Pd metal can be directly detected in PdO/CeO2 catalysts supported on X-Al2O3 by means of in situ high-temperature measurements of X-ray diffraction and FF-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 O-2-deficient and O-2-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.