Effect of the Reduction Step on the Catalytic Performance of Pd-CeMO2 Based Catalysts (M = Gd, Zr) for Propane Combustion

The effect of a reduction step on the catalytic activity of Pd supported doped ceria catalysts was investigated for the propane combustion. Two different oxides based on ceria zirconia (CZ), as a reference three-way catalyst support, and Gadolinia doped ceria (GDC), a mixed ionic electronic conductor, have been used to support Pd nanoparticles. The samples were characterized by H-2-CO chemisorption, temperature programmed reduction, and XPS. In addition, the reduction step in H-2 was in situ observed by environmental transmission electron microscopy. It was found that the catalytic activity of Pd supported on ceria-based supports can be strongly promoted by a reduction step whereas it does not change on alumina. This effect was attributed, in particular on GDC, to the reduction of a surface interaction phase, PdxCeO2-delta, which induces a re-dispersion of metallic Pd nanoparticles.