Redox Property–Local Structure Relationships in the Rh-Loaded CeO₂–ZrO₂Mixed Oxides

Author： Vlaic G. Di Monte R. Fornasiero P. Fonda E. Kašpar J. Graziani M.

ISSN： 0021-9517

Source： Journal of Catalysis, Vol.182, Iss.2, 1999-03, pp. : 378-389

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Abstract

The local structure of the M–O bond in CeO₂–ZrO₂mixed oxides is investigated with the aim of finding a correlation between structural parameters and oxygen exchange properties. It is found that insertion of ZrO₂into the CeO₂lattice strongly perturbs the symmetry of the M–O bond. As the content of CeO₂in CeO₂–ZrO₂solid solution is increased from 20 to 80 mol%, tetragonal, (t,t^′,t^″) and cubic phases are formed. The local symmetry of the Zr–O bond is strongly perturbed by the increase in CeO₂content while no significant modification of the first Ce–O coordination sphere is found, except for lengthening of the Ce–O bond consistent with lattice parameter increase. The perturbation of the Zr–O coordination sphere, which leads to highly disordered oxygen in the lattice, is indicated as responsible for the high oxygen mobility in CeO₂–ZrO₂mixed oxides.