Nanostructured ceria-zirconia catalysts for CO oxidation: Study on surface properties and reactivity
•Ceria-zirconia nanomaterials are active for CO oxidation.•Ceria-zirconia nano-polyhedra showed the highest activity towards CO oxidation.•Worse performances have been obtained for porous catalysts with the same Ce/Zr ratio.•The most active catalyst showed better redox properties and easier surface reducibility.•CO oxidation over Ce-Zr mixed oxides is a structure-sensitive reaction.
In the present work, a set of Ce-Zr-O catalysts was prepared to study the effect of Zr-content (in the range 10–30 at.%) and the surface-dependency activity towards CO oxidation, a prototypical reaction for oxidation catalysis. The physico-chemical features of the prepared materials were investigated using complementary techniques.As a whole, it was observed that the oxidation activity of ceria-zirconia nanocatalysts mainly depends on the presence of (100) and (110) crystalline planes, thus confirming the structure-sensitivity for this reaction over Ce-Zr mixed oxides. Moreover, the abundant population of carbonate-like species on more open and reactive surfaces has a beneficial effect on the reactivity of the Ce-Zr-O nanomaterials.The best compromise between the structural defects and redox-active centres (Ce3+/Ce4+ pairs) was observed for the most active nanocatalyst, namely the Ce0.9Zr0.1O2NP (nanopolyhedra with sizes of about 20–40 nm). The latter exhibited better CO conversion values compared to similar Ce-Zr-O nanocatalysts with higher Zr-contents (namely, Ce0.8Zr0.2O2NP and Ce0.7Zr0.3O2NP). On the other hand, lower activities were obtained for the high-surface-area catalysts (e.g. mesostructured materials) with the same Ce/Zr ratio, thus showing the key role played by the structural features of solid catalysts for this reaction.
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Journal: Applied Catalysis B: Environmental - Volume 197, 15 November 2016, Pages 35–46