Unexpected trends in the enhanced Ce3+surface concentration in ceria-zirconia catalyst materials

Weizi Yuan, Qing Ma, Yangang Liang, Chengjun Sun, K. V.L.V. Narayanachari, Michael J. Bedzyk, Ichiro Takeuchi, Sossina M. Haile*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Despite the immense importance of ceria-zirconia solid solutions in heterogeneous catalysis, and the growing consensus that catalytic activity correlates with the concentration of reduced Ce3+species and accompanying oxygen vacancies, the extent of reduction at the surfaces of these materials, where catalysis occurs, is unknown. Using angle-resolved X-ray Absorption Near Edge Spectroscopy (XANES), we quantify under technologically relevant conditions the Ce3+concentration in the surface (2-3 nm) and bulk regions of ceria-zirconia films grown on single crystal yttria-stabilized zirconia, YSZ (001). In all circumstances, we observe substantial Ce3+enrichment at the surface relative to the bulk. Surprisingly, the degree of enhancement is highest in the absence of Zr. This behavior stands in direct contrast to that of the bulk in which the Ce3+concentration monotonically increases with increasing Zr content. These results suggest that while Zr enhances the oxygen storage capacity in ceria, undoped ceria may have higher surface catalytic activity. They further urge caution in the use of bulk properties as surrogate descriptors for surface characteristics and hence catalytic activity.

Original languageEnglish (US)
Pages (from-to)9850-9858
Number of pages9
JournalJournal of Materials Chemistry A
Volume8
Issue number19
DOIs
StatePublished - May 21 2020

ASJC Scopus subject areas

  • Chemistry(all)
  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

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