Understanding of Enhanced Oxygen Storage Capacity in Ce_0.5Zr_0.5O₂:  The Presence of an Anharmonic Pair Distribution Function in the Zr−O₂ Subshell as Analyzed by XAFS Spectroscopy

Abstract

Standard EXAFS analysis on Ce x Zr 1-x O 2 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 Ce 0.5 Zr 0.5 O 2 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 Ce 0.5 Zr 0.5 O 2 . 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 capacity is determined by the interlayer Zr-O interaction.

Thermogravimetric Analysis of Zirconia-Doped Ceria for Thermochemical Production of Solar Fuel

“…The reduction from Ce 4+ to Ce 3+ causes the lattice to expand, since Ce 4+ exhibits a smaller ionic radius resulting in a stress that suppresses further reduction [49]. Introducing Zr 4+ into the fluorite structure of ceria compensates for the expansion of the crystal lattice, since Zr 4+ ions are smaller than Ce 4+ and Ce 3+ ions [46,50].…”

Recent Advances in Hydrogen Production Via Autothermal Reforming Process (ATR): A Review of Patents and Research Articles

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Techniques for the Study of the Structural Properties

“…Analysis of the EXAFS data of nanostructured oxides which account for the relative asymmetric (anharmonic) pair distribution of bond distances are even more scarce and exclusively devoted to Ti and Ce oxide systems 49,50 . This however has been frequently worked out for nanostructured chalcogenides 51 and has been studied in detail for nanostructured fcc metals 52 .…”