Nanostructured ceria-zirconia catalysts for CO oxidation: Study on surface properties and reactivity

Abstract

In the present work, a set of Ce-Zr-O catalysts was prepared to study the effect of Zr-content (in the range 10–30at.%) 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 20–40nm). 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.