Schilling, Christian ; Hess, Christian (2019)
Elucidating the role of support oxygen in the water–gas shift reaction over ceria-supported gold catalysts using operando spectroscopy.
In: ACS Catalysis, 9 (2)
doi: 10.1021/acscatal.8b04536
Artikel, Bibliographie
Dies ist die neueste Version dieses Eintrags.
Kurzbeschreibung (Abstract)
Supported-metal (Au, Pt) ceria-based catalysts are considered as promising candidates for the water–gas shift (WGS) reaction at low temperatures. Two main mechanisms have been proposed in the literature, the redox and associative mechanisms. A key step in both mechanisms has been considered to be the cleavage of O–H bonds. In this mechanistic study, the role of surface and bulk oxygen species involved in the WGS reaction over ceria-supported gold catalysts (Au/CeO₂) was elucidated directly using operando Raman spectroscopy combined with isotope labeling and supported by DFT+U calculations. Exposure of Au/CeO₂ to pure H₂¹⁸O results in a complete replacement of surface ¹⁶O ions by ¹⁸O ions as rationalized by dissociative adsorption of H₂¹⁸O in the presence of a surface oxygen vacancy and a subsequent backward reaction restoring lattice oxygen as ¹⁸O and releasing H₂¹⁶O. This reaction pathway is accessible even in the absence of CO. Exposure to reaction conditions leads to (i) a complete disappearance of the Ce–O surface modes due to hydroxyl formation, (ii) a Raman F₂g redshift due to reduction of the ceria subsurface, leading to a change in stoichiometry from CeO₁.₉₄₇₋ₓ (in argon) to CeO₁.₈₇₃₋ₓ (in CO/H₂¹⁶O), and (iii) large amounts of ¹⁸O in the subsurface of the ceria support due to oxygen transfer from the surface to the ceria subsurface, highlighting the oxygen dynamics of the ceria support. While the results of this study are fully consistent with a redox mechanism involving a reaction pathway for replenishment of surface oxygen ions O²⁻ from terminal hydroxyl groups (O–H) accessible also in the absence of CO in the gas phase, other reaction mechanisms cannot be ruled out.
| Typ des Eintrags: | Artikel |
|---|---|
| Erschienen: | 2019 |
| Autor(en): | Schilling, Christian ; Hess, Christian |
| Art des Eintrags: | Bibliographie |
| Titel: | Elucidating the role of support oxygen in the water–gas shift reaction over ceria-supported gold catalysts using operando spectroscopy |
| Sprache: | Englisch |
| Publikationsjahr: | 2019 |
| Verlag: | American Chemical Society |
| Titel der Zeitschrift, Zeitung oder Schriftenreihe: | ACS Catalysis |
| Jahrgang/Volume einer Zeitschrift: | 9 |
| (Heft-)Nummer: | 2 |
| DOI: | 10.1021/acscatal.8b04536 |
| Zugehörige Links: | |
| Kurzbeschreibung (Abstract): | Supported-metal (Au, Pt) ceria-based catalysts are considered as promising candidates for the water–gas shift (WGS) reaction at low temperatures. Two main mechanisms have been proposed in the literature, the redox and associative mechanisms. A key step in both mechanisms has been considered to be the cleavage of O–H bonds. In this mechanistic study, the role of surface and bulk oxygen species involved in the WGS reaction over ceria-supported gold catalysts (Au/CeO₂) was elucidated directly using operando Raman spectroscopy combined with isotope labeling and supported by DFT+U calculations. Exposure of Au/CeO₂ to pure H₂¹⁸O results in a complete replacement of surface ¹⁶O ions by ¹⁸O ions as rationalized by dissociative adsorption of H₂¹⁸O in the presence of a surface oxygen vacancy and a subsequent backward reaction restoring lattice oxygen as ¹⁸O and releasing H₂¹⁶O. This reaction pathway is accessible even in the absence of CO. Exposure to reaction conditions leads to (i) a complete disappearance of the Ce–O surface modes due to hydroxyl formation, (ii) a Raman F₂g redshift due to reduction of the ceria subsurface, leading to a change in stoichiometry from CeO₁.₉₄₇₋ₓ (in argon) to CeO₁.₈₇₃₋ₓ (in CO/H₂¹⁶O), and (iii) large amounts of ¹⁸O in the subsurface of the ceria support due to oxygen transfer from the surface to the ceria subsurface, highlighting the oxygen dynamics of the ceria support. While the results of this study are fully consistent with a redox mechanism involving a reaction pathway for replenishment of surface oxygen ions O²⁻ from terminal hydroxyl groups (O–H) accessible also in the absence of CO in the gas phase, other reaction mechanisms cannot be ruled out. |
| Freie Schlagworte: | ceria, gold, water−gas shift, operando Raman spectroscopy, isotope exchange, reaction mechanism |
| Fachbereich(e)/-gebiet(e): | 07 Fachbereich Chemie 07 Fachbereich Chemie > Eduard Zintl-Institut 07 Fachbereich Chemie > Eduard Zintl-Institut > Fachgebiet Physikalische Chemie Zentrale Einrichtungen Zentrale Einrichtungen > Hochschulrechenzentrum (HRZ) Zentrale Einrichtungen > Hochschulrechenzentrum (HRZ) > Hochleistungsrechner |
| Hinterlegungsdatum: | 11 Jan 2019 10:23 |
| Letzte Änderung: | 30 Okt 2024 09:12 |
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Verfügbare Versionen dieses Eintrags
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Elucidating the Role of Support Oxygen in the Water–Gas Shift Reaction over Ceria-Supported Gold Catalysts Using Operando Spectroscopy. (deposited 29 Okt 2024 13:32)
- Elucidating the role of support oxygen in the water–gas shift reaction over ceria-supported gold catalysts using operando spectroscopy. (deposited 11 Jan 2019 10:23) [Gegenwärtig angezeigt]
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