Understanding of enhanced oxygen storage capacity in Ce0.5Zr0.5O2: The presence of an anharmonic pair distribution function in the Zr-O-2 subshell asanalyzed by XAFS spectroscopy

Standard EXAFS analysis on CexZr1-xO2 mixed oxides leads to incorrect struc tural parameters. A comparison of XRD Rietveld analysis with an EXAFS study of a Y-doped reference compound and a Ce0.5Zr0.5O2 catalyst showed that in order to obtain reliable structural parameters with EXAFS an anharmonic pa ir distribution function has to be used for the analysis of the second Zr-O bond. The anharmonicity of the second Zr-O subshell points to a much weake r Zr-O bond than in the first Zr-O subshell. A lamellar type structural mod el explains the high oxygen storage capacity of Ce0.5Zr0.5O2. The short Zr- O-1 distance corresponds to the intralayer Zr-O bond and the much weaker Zr -O-2 distance to the interlayer Zr-O interaction. The oxygen storage capaci ty is determined by the interlayer Zr-O interaction.