Higher activity of Diesel soot oxidation over polycrystalline ceria and ceria-zirconia solid solutions from more reactive surface planes

High temperature treatment under air of samples of polycrystalline ceria and ceria- zirconia is shown to induce a rearrangement of crystals, with a surface structural evolution of the oxides toward the formation of more reactive exposed planes belonging to the {1 0 0} and {1 1 0} families, associated with a decrease of the exposure of the less reactive {1 1 1} facets. This is dependent on the amount of ceria, being more evident with pure CeO2, and less important with increasing ZrO2 content. A correlation between the exposure of more reactive planes and the specific rate of carbon soot oxidation is found, in agreement with previous results obtained in monodimensional nanoshaped and polycrystalline ceria samples for CO oxidation. This suggests that Diesel soot oxidation catalysts might be designed by keeping into consideration also these effects.