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Title: Water–gas shift reaction over gold nanoparticles dispersed on nanostructured CeO x–TiO 2(110) surfaces: Effects of high ceria coverage

Abstract

We used scanning tunnelling microscopy to study the morphology of an overlayer of ceria in contact with a TiO 2(110) substrate. Two types of domains were observed after ceria deposition. An ordered ceria film covered half of the surface and high-resolution imaging suggested a near-c(6 × 2) relationship to the underlying TiO 2(110)-(1 × 1). For the other half of the surface, it comprised CeO x nanoparticles and reconstructed TiOx supported on TiO 2(110)-(1 × 1). Exposure to a small amount of gold resulted in the formation of isolated gold atoms and small clusters on the ordered ceria film and TiO 2(110)-(1 × 1) areas, which exhibited significant sintering at 500 K and showed strong interaction between the sintered gold clusters and the domain boundaries of the ceria film. The Au/CeO x/TiO 2(110) model system proved to be a good catalyst for the water–gas shift (WGS) exhibiting much higher turnover frequencies (TOFs) than Cu(111) and Pt(111) benchmarks, or the individual Au/TiO 2(110) and Au/CeO 2(111) systems. Finally, for Au/CeO x/TiO 2(110) catalysts, there was a decrease in catalytic activity with increasing ceria coverage that correlates with a reduction in the concentration of Ce 3 + formed during WGS reaction conditions.

Authors:
 [1];  [1];  [1];  [2];  [1];  [1];  [1];  [1]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
  2. Central Univ. of Venezuela, Caracas (Venezuela)
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1303023
Report Number(s):
BNL-112519-2016-JA; BNL-113208-2016-JA
Journal ID: ISSN 0039-6028; R&D Project: CO009; KC0302010
Grant/Contract Number:
SC00112704; SC0012704
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Surface Science
Additional Journal Information:
Journal Volume: 650; Journal Issue: C; Journal ID: ISSN 0039-6028
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; STM; TiO2 (110); CeO2; gold; water-gas shift; TiO2(110); water–gas shift

Citation Formats

Grinter, D. C., Park, J. B., Agnoli, S., Evans, J., Hrbek, J., Stacchiola, D. J., Senanayake, S. D., and Rodriguez, J. A. Water–gas shift reaction over gold nanoparticles dispersed on nanostructured CeOx–TiO2(110) surfaces: Effects of high ceria coverage. United States: N. p., 2016. Web. doi:10.1016/j.susc.2015.10.002.
Grinter, D. C., Park, J. B., Agnoli, S., Evans, J., Hrbek, J., Stacchiola, D. J., Senanayake, S. D., & Rodriguez, J. A. Water–gas shift reaction over gold nanoparticles dispersed on nanostructured CeOx–TiO2(110) surfaces: Effects of high ceria coverage. United States. doi:10.1016/j.susc.2015.10.002.
Grinter, D. C., Park, J. B., Agnoli, S., Evans, J., Hrbek, J., Stacchiola, D. J., Senanayake, S. D., and Rodriguez, J. A. 2016. "Water–gas shift reaction over gold nanoparticles dispersed on nanostructured CeOx–TiO2(110) surfaces: Effects of high ceria coverage". United States. doi:10.1016/j.susc.2015.10.002. https://www.osti.gov/servlets/purl/1303023.
@article{osti_1303023,
title = {Water–gas shift reaction over gold nanoparticles dispersed on nanostructured CeOx–TiO2(110) surfaces: Effects of high ceria coverage},
author = {Grinter, D. C. and Park, J. B. and Agnoli, S. and Evans, J. and Hrbek, J. and Stacchiola, D. J. and Senanayake, S. D. and Rodriguez, J. A.},
abstractNote = {We used scanning tunnelling microscopy to study the morphology of an overlayer of ceria in contact with a TiO2(110) substrate. Two types of domains were observed after ceria deposition. An ordered ceria film covered half of the surface and high-resolution imaging suggested a near-c(6 × 2) relationship to the underlying TiO2(110)-(1 × 1). For the other half of the surface, it comprised CeOx nanoparticles and reconstructed TiOx supported on TiO2(110)-(1 × 1). Exposure to a small amount of gold resulted in the formation of isolated gold atoms and small clusters on the ordered ceria film and TiO2(110)-(1 × 1) areas, which exhibited significant sintering at 500 K and showed strong interaction between the sintered gold clusters and the domain boundaries of the ceria film. The Au/CeOx/TiO2(110) model system proved to be a good catalyst for the water–gas shift (WGS) exhibiting much higher turnover frequencies (TOFs) than Cu(111) and Pt(111) benchmarks, or the individual Au/TiO2(110) and Au/CeO2(111) systems. Finally, for Au/CeOx/TiO2(110) catalysts, there was a decrease in catalytic activity with increasing ceria coverage that correlates with a reduction in the concentration of Ce3 + formed during WGS reaction conditions.},
doi = {10.1016/j.susc.2015.10.002},
journal = {Surface Science},
number = C,
volume = 650,
place = {United States},
year = 2016,
month = 8
}

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  • In this study, scanning tunnelling microscopy has been used to study the morphology of an overlayer of ceria in contact with a TiO 2(110) substrate. Two types of domains were observed after ceria deposition. An ordered ceria film covered half of the surface and high-resolution imaging suggested a near-c(6 × 2) relationship to the underlying TiO 2(110)-(1 × 1). The other half of the surface comprised CeO x nanoparticles and reconstructed TiOx supported on TiO 2(110)-(1 × 1). Exposure to a small amount of gold resulted in the formation of isolated gold atoms and small clusters on the ordered ceriamore » film and TiO 2(110)-(1 × 1) areas, which exhibited significant sintering at 500 K and showed strong interaction between the sintered gold clusters and the domain boundaries of the ceria film. The Au/CeO x/TiO 2(110) model system proved to be a good catalyst for the water–gas shift (WGS) exhibiting much higher turnover frequencies (TOFs) than Cu(111) and Pt(111) benchmarks, or the individual Au/TiO 2(110) and Au/CeO 2(111) systems. For Au/CeO x/TiO 2(110) catalysts, there was a decrease in catalytic activity with increasing ceria coverage that correlates with a reduction in the concentration of Ce 3+ formed during WGS reaction conditions.« less
  • At small coverages of ceria on TiO{sub 2}(110), the CeO{sub x} nanoparticles have an unusual coordination mode. Scanning tunneling microscopy and density-functional calculations point to the presence of Ce{sub 2}O{sub 3} dimers, which form diagonal arrays that have specific orientations of 0, 24, and 42{sup o} with respect to the [1 -1 0] direction of the titania substrate. At high coverages of ceria on TiO{sub 2}(110), the surface exhibits two types of terraces. In one type, the morphology is not very different from that observed at low ceria coverage. However, in the second type of terrace, there is a compactmore » array of ceria particles with structures that do not match the structures of CeO{sub 2}(111) or CeO{sub 2}(110). The titania substrate imposes on the ceria nanoparticles nontypical coordination modes, enhancing their chemical reactivity. This phenomenon leads to a larger dispersion of supported metal nanoparticles (M = Au, Cu, Pt) and makes possible the direct participation of the oxide in catalytic reactions. The M/CeO{sub x}/TiO{sub 2}(110) surfaces display an extremely high catalytic activity for the water-gas shift reaction that follows the sequence Au/CeO{sub x}/TiO{sub 2}(110) < Cu/CeO{sub x}/TiO{sub 2}(110) < Pt/CeO{sub x}/TiO{sub 2}(110). For low coverages of Cu and CeO{sub x}, Cu/CeO{sub x}/TiO{sub 2}(110) is 8-12 times more active than Cu(111) or Cu/ZnO industrial catalysts. In the M/CeO{sub x}/TiO{sub 2}(110) systems, there is a strong coupling of the chemical properties of the admetal and the mixed-metal oxide: The adsorption and dissociation of water probably take place on the oxide, CO adsorbs on the admetal nanoparticles, and all subsequent reaction steps occur at the oxide-admetal interface. The high catalytic activity of the M/CeO{sub x}/TiO{sub 2}(110) surfaces reflects the unique properties of the mixed-metal oxide at the nanometer level.« less
  • At small coverages of ceria on TiO{sub 2}(110), the CeO{sub x} nanoparticles have an unusual coordination mode. Scanning tunneling microscopy and density-functional calculations point to the presence of Ce{sub 2}O{sub 3} dimers, which form diagonal arrays that have specific orientations of 0, 24, and 42{sup o} with respect to the [1 -1 0] direction of the titania substrate. At high coverages of ceria on TiO{sub 2}(110), the surface exhibits two types of terraces. In one type, the morphology is not very different from that observed at low ceria coverage. However, in the second type of terrace, there is a compactmore » array of ceria particles with structures that do not match the structures of CeO{sub 2}(111) or CeO{sub 2}(110). The titania substrate imposes on the ceria nanoparticles nontypical coordination modes, enhancing their chemical reactivity. This phenomenon leads to a larger dispersion of supported metal nanoparticles (M = Au, Cu, Pt) and makes possible the direct participation of the oxide in catalytic reactions. The M/CeO{sub x}/TiO{sub 2}(110) surfaces display an extremely high catalytic activity for the water-gas shift reaction that follows the sequence Au/CeO{sub x}/TiO{sub 2}(110) < Cu/CeO{sub x}/TiO{sub 2}(110) < Pt/CeO{sub x}/TiO{sub 2}(110). For low coverages of Cu and CeO{sub x}, Cu/CeO{sub x}/TiO{sub 2}(110) is 8-12 times more active than Cu(111) or Cu/ZnO industrial catalysts. In the M/CeO{sub x}/TiO{sub 2}(110) systems, there is a strong coupling of the chemical properties of the admetal and the mixed-metal oxide: The adsorption and dissociation of water probably take place on the oxide, CO adsorbs on the admetal nanoparticles, and all subsequent reaction steps occur at the oxide-admetal interface. The high catalytic activity of the M/CeO{sub x}/TiO{sub 2}(110) surfaces reflects the unique properties of the mixed-metal oxide at the nanometer level.« less