Reactivity of ultra-thin ZnO films supported by Ag(111) and Cu(111): A comparison to ZnO/Pt(111)

Q. Pan, B. H. Liu, M. E. McBriarty, Y. Martynova, I. M.N. Groot, S. Wang, M. J. Bedzyk, S. Shaikhutdinov*, H. J. Freund

*Corresponding author for this work

Research output: Contribution to journalArticle

38 Scopus citations

Abstract

We studied structure and reactivity of ZnO(0001) ultrathin films grown on Ag(111) and Cu(111) single crystal surfaces. Structural characterization was carried out by scanning tunneling microscopy, Auger electron spectroscopy, low-energy electron diffraction, and temperature programmed desorption. The CO oxidation behavior of the films was studied at low temperature (450 K) at near atmospheric pressures using gas chromatography. For ZnO/Cu(111), it is shown that under reaction conditions ZnO readily migrates into the Cu crystal bulk, and the reactivity is governed by a CuOx oxide film formed in the reaction ambient. In contrast, the planar structure of ZnO films on Ag(111) is maintained, similarly to the previously studied ZnO films on Pt(111). At sub-monolayer coverages, the "inverse" model catalysts are represented by two-monolayer-thick ZnO(0001) islands on Pt(111) and Ag(111) supports. While the CO oxidation rate is considerably increased on ZnO/Pt(111), which is attributed to active sites at the metal/oxide boundary, sub-monolayer ZnO films on Ag(111) did not show such an effect, and the reactivity was inhibited with increasing film coverage. The results are explained by much stronger adsorption of CO on Pt(111) as compared with Ag(111) in proximity to O species at the oxide/metal boundary. In addition, the water-gas shift and reverse water-gas shift reactions were examined on ZnO/Ag(111), which revealed no promotional effect of ZnO on the reactivity of Ag under the conditions studied. The latter finding suggests that wetting phenomena of ZnO on metals does not play a crucial role in the catalytic performance of ZnO-based real catalysts in those reactions. Graphical Abstract: [Figure not available: see fulltext.]

Original languageEnglish (US)
Pages (from-to)648-655
Number of pages8
JournalCatalysis Letters
Volume144
Issue number4
DOIs
StatePublished - Apr 2014

Keywords

  • CO oxidation
  • Inverse catalysts
  • Thin oxide films
  • Zinc oxide

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

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    Pan, Q., Liu, B. H., McBriarty, M. E., Martynova, Y., Groot, I. M. N., Wang, S., Bedzyk, M. J., Shaikhutdinov, S., & Freund, H. J. (2014). Reactivity of ultra-thin ZnO films supported by Ag(111) and Cu(111): A comparison to ZnO/Pt(111). Catalysis Letters, 144(4), 648-655. https://doi.org/10.1007/s10562-014-1191-y