Study of the Structural Modifications Induced by Reducing Treatments on a Pd/Ce0.8Tb0.2O2 - x /La2O3−Al2O3 Catalyst by Means of X-ray Diffraction and Electron Microscopy Techniques

X-ray diffraction with Rietveld analysis, EDS, HREM, and CO oxidation experiments have been used to study the nanoscale evolution with reduction temperature of a Pd/Ce0.8Tb0.2O2 - x /La2O3−Al2O3 catalyst. Up to 700 °C, both Pd and the Ce0.8Tb0.2O2 - x mixed oxide are present as nanosized particles that are well-dispersed over the La-modified alumina support. After reduction at 900 °C, severe sintering of the metallic Pd particles occurs, along with the formation of a perovkite phase LnAlO3 with variable content of trivalent lanthanide ions (Ln3+ = La3+, Ce3+, and Tb3+). Parallel deactivation of the catalyst for the CO oxidation reaction is observed upon increasing reduction temperature.