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

doi:10.1007/s10562-014-1191-y

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

Materials Science and Engineering

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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 CuO_x 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 language	English (US)
Pages (from-to)	648-655
Number of pages	8
Journal	Catalysis Letters
Volume	144
Issue number	4
DOIs	https://doi.org/10.1007/s10562-014-1191-y
State	Published - Apr 2014

Keywords

CO oxidation
Inverse catalysts
Thin oxide films
Zinc oxide

ASJC Scopus subject areas

Catalysis
Chemistry(all)

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10.1007/s10562-014-1191-y

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@article{977f6b89843942d0824d0ca20599d01e,

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

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.]",

keywords = "CO oxidation, Inverse catalysts, Thin oxide films, Zinc oxide",

author = "Q. Pan and Liu, {B. H.} and McBriarty, {M. E.} and Y. Martynova and Groot, {I. M.N.} and S. Wang and Bedzyk, {M. J.} and S. Shaikhutdinov and Freund, {H. J.}",

note = "Funding Information: Acknowledgments The work has been supported by Fonds der Chemischen Industrie, Deutsche Forschungsgemeinschaft, and Cluster of Excellence {\textquoteleft}{\textquoteleft}UniCat{\textquoteright}{\textquoteright}, in particular through the Northwestern University – CoE {\textquoteleft}{\textquoteleft}UniCat{\textquoteright}{\textquoteright} collaboration. BHL acknowledges the International Max Planck Research School {\textquoteleft}{\textquoteleft}Complex surfaces in materials science{\textquoteright}{\textquoteright}. MEM was a Fulbright Grantee in the Graduate Fellow Student Program 2011–2012. MEM and MJB were supported in part by US Department of Energy Grant No. DE-FG02-03ER15457. IMNG thanks the Alexander von Humboldt Foundation for a fellowship. The FHI team acknowledges the support from the COST Action CM1104 {\textquoteleft}{\textquoteleft}Reducible oxide chemistry, structure and functions{\textquoteright}{\textquoteright}.",

year = "2014",

month = apr,

doi = "10.1007/s10562-014-1191-y",

language = "English (US)",

volume = "144",

pages = "648--655",

journal = "Catalysis Letters",

issn = "1011-372X",

publisher = "Springer Netherlands",

number = "4",

}

TY - JOUR

T1 - Reactivity of ultra-thin ZnO films supported by Ag(111) and Cu(111)

T2 - A comparison to ZnO/Pt(111)

AU - Pan, Q.

AU - Liu, B. H.

AU - McBriarty, M. E.

AU - Martynova, Y.

AU - Groot, I. M.N.

AU - Wang, S.

AU - Bedzyk, M. J.

AU - Shaikhutdinov, S.

AU - Freund, H. J.

N1 - Funding Information: Acknowledgments The work has been supported by Fonds der Chemischen Industrie, Deutsche Forschungsgemeinschaft, and Cluster of Excellence ‘‘UniCat’’, in particular through the Northwestern University – CoE ‘‘UniCat’’ collaboration. BHL acknowledges the International Max Planck Research School ‘‘Complex surfaces in materials science’’. MEM was a Fulbright Grantee in the Graduate Fellow Student Program 2011–2012. MEM and MJB were supported in part by US Department of Energy Grant No. DE-FG02-03ER15457. IMNG thanks the Alexander von Humboldt Foundation for a fellowship. The FHI team acknowledges the support from the COST Action CM1104 ‘‘Reducible oxide chemistry, structure and functions’’.

PY - 2014/4

Y1 - 2014/4

N2 - 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.]

AB - 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.]

KW - CO oxidation

KW - Inverse catalysts

KW - Thin oxide films

KW - Zinc oxide

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U2 - 10.1007/s10562-014-1191-y

DO - 10.1007/s10562-014-1191-y

M3 - Article

AN - SCOPUS:84900634402

SN - 1011-372X

VL - 144

SP - 648

EP - 655

JO - Catalysis Letters

JF - Catalysis Letters

IS - 4

ER -

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

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