Nanostructured ceria-based catalysts for soot combustion: Investigations on the surface sensitivity

Abstract

A set of ceria nanomaterials with different topological and textural properties has been prepared to investigate the shape-dependency activity of ceria towards soot combustion under different reaction conditions (namely in “loose” and “tight” contact). The physico-chemical properties of the prepared catalysts have been studied using complementary techniques. The best performances, in terms of the total oxidation of soot, have been achieved for the CeO2-nanocubes, due to the abundance of coordinative unsaturated atomic sites on the (100) and (110) exposed surfaces (namely truncated nanocubes). However, better results, in terms of the onset of soot oxidation, have been obtained for high-surface-area materials, thus reflecting the key role of surface area at low temperatures. Activity tests have suggested the surface-sensitivity of soot oxidation over the prepared ceria-based materials, when the reaction temperature was above 410°C or 370°C (in “loose” or “tight” conditions, respectively). On the other hand, the reaction has appeared surface-insensitive at a lower temperature. Hence, soot oxidation over these ceria compounds can be considered a reaction that displays both surface-sensitive and surface-insensitive behaviour, which depend on the experimental conditions.