Rhodium supported on modified zirconia, prepared by sol-gel method and containing trivalent elements in the 0–3% wt. range, have been prepared and characterised in terms of (i) structural properties, (ii) surface reactivity towards reducibility and reoxidizability in mild conditions, (iii) dispersion, surface area and stability against sintering of the metallic Rh particles and (iv) reactivity in the N2O decomposition in the presence of O2. The introduction of small amounts of trivalent elements in the zirconia structure stabilises the formation of oxygen vacancies and the reducibility of the catalyst, but up to a maximum corresponding to about 1% wt. of the element, after which the further increase of the trivalent element has a negative effect due to the formation of extended ordered defects. The dispersion of Rh and the stability of the Rh particles against the sintering follows the same parallel trend of the catalyst reducibility, and a similar trend in observed also in the reactivity of these catalysts in the decomposition of N2O in the presence of oxygen and water in the feed. These results suggest the role of the oxygen vacancies (point defects) at the Rh-zirconia interface on the promotion of the properties of supported Rh particles, in terms of both dispersion, stability and catalytic reactivity.
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