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 degreesC, 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 degreesC, severe sintering of the metallic Pd particles occurs, along with the formation of a perovkite phase LnAlO(3) with variable content of trivalent lanthanide ions (Ln(3+) = La3+, Ce3+, and Tb3+). Parallel deactivation of the catalyst for the CO oxidation reaction is observed upon increasing reduction temperature.