Reaction Mechanisms for the CO Oxidation on Au/CeO Catalysts: Activity of Substitutional Au/AuCations and Deactivation of Supported Au Adatoms.
Density functional theory calculations that account for the on-site Coulomb interaction via a Hubbard term (DFT+U) reveal the mechanisms for the oxidation of CO catalyzed by isolated Au atoms as well as small clusters in Au/CeO catalysts. Ceria (111) surfaces containing positively charged Au ions, e...
| Publicado en: | Journal of the American Chemical Society Vol. 131; no. 30; pp. 10473 - 10484 |
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| Autores principales: | , |
| Formato: | Artículo |
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American Chemical Society
8/5/2009
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| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=43925589&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 43925589 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 8/5/2009 vid: 131 iid: 30 pid: 997 pub: American Chemical Society artinfo: ui: 43925589 10.1021/ja902109k ppf: 10473 ppct: 11 formats: tig: atl: Reaction Mechanisms for the CO Oxidation on Au/CeO Catalysts: Activity of Substitutional Au/AuCations and Deactivation of Supported Au Adatoms. aug: au: Camellone, Matteo Farnesi Fabris, Stefano affil: Theory@Elettra Group, INFM-CNR DEMOCRITOS, c/o Sincrotrone Trieste-SS14, Km 163, 5 Basovizza, 1-34012 Trieste, Italy SISSA Scuola Internazionale Superiore di Studi Avanzati, via Beirut 2-4, 1-34014 Trieste, Italy su: Density functionals Carbon monoxide Gold Cations Oxidation Catalysts Nanoparticles sug: subj: Density functionals Carbon monoxide Gold Cations Oxidation Catalysts Nanoparticles ab: Density functional theory calculations that account for the on-site Coulomb interaction via a Hubbard term (DFT+U) reveal the mechanisms for the oxidation of CO catalyzed by isolated Au atoms as well as small clusters in Au/CeO catalysts. Ceria (111) surfaces containing positively charged Au ions, either as supported Au adatoms or as substitutional Au ions, are shown to activate molecular CO and to catalyze its oxidation to CO. In the case of supported single Au adatoms, the limiting rate for the CO oxidation is determined by the adsorbate spillover from the adatom to the oxide support. The reaction then proceeds with the CO oxidation via lattice oxygen and O vacancy formation. These vacancies are shown to readily attract the supported Au adatoms and to turn them into negatively charged Au adspecies that deactivate the catalyst, preventing further CO adsorption. Au ions dispersed into the ceria lattice as substitutional point defects can instead sustain a full catalytic cycle consisting of three individual steps maintaining their activity along the reaction process: Au cations in AuCeO systems promote multiple oxidations of CO without any activation energy via formation of surface O vacancies. Molecular oxygen adsorbs at these vacancies and forms O adspecies that then catalyze the oxidation of molecular CO, closing the catalytic cycle and recovering the stoichiometric AuCeO system. The interplay between the reversible Ce/Ce and Au/Au reductions underpins the high catalytic activity of dispersed Au atoms into the ceria substrate. It is shown that the positive oxidation state of the substitutional Au ions is retained along the catalytic cycle, thus preventing the deactivation of AuCeO catalysts in operation conditions. Finally, although a single Au adatom bound to an O vacancy is shown to deactivate during CO oxidation, the calculations predict that the reactivity of gold nanoparticles nucleated at O vacancies can be recovered for cluster sizes as small as Au. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2009 holdings: @attributes: islocal: N |
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