Understanding of Enhanced Oxygen Storage Capacity in Ce0.5Zr0.5O2: The Presence of an Anharmonic Pair Distribution Function in the Zr−O2 Subshell as Analyzed by XAFS Spectroscopy

Standard EXAFS analysis on CexZr1-xO2 mixed oxides leads to incorrect structural 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 pair 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 weaker Zr−O bond than in the first Zr−O subshell. A lamellar type structural model explains the high oxygen storage capacity of Ce0.5Zr0.5O2. The short Zr−O1 distance corresponds to the intralayer Zr−O bond and the much weaker Zr−O2 distance to the interlayer Zr−O interaction. The oxygen storage capacity is determined by the interlayer Zr−O interaction.