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

• Ceria-based nanomaterials for soot combustion.
• Ceria-nanocubes showed the highest activity towards total oxidation of soot.
• Structure-sensitivity of soot oxidation over ceria-based materials.
• At low temperature the soot oxidation reaction behaves as structure insensitive.

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 (1 0 0) and (1 1 0) 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.

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