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          Institute: Fritz-Haber-Institut     Collection: Inorganic Chemistry     Display Documents



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ID: 400269.0, Fritz-Haber-Institut / Inorganic Chemistry
Analysis of silica-supported vanadia by X-ray absorption spectroscopy: Combined theoretical and experimental studies
Authors:Cavalleri, Matteo; Hermann, Klaus; Knop-Gericke, Axel; Hävecker, Michael; Herbert, R.; Hess, Christian; Oestereich, Andreas; Döbler, J.; Schlögl, Robert
Language:English
Research Context:XAS on supported vanadium
Date of Publication (YYYY-MM-DD):2009-03-10
Title of Journal:Journal of Catalysis
Journal Abbrev.:J. Catal.
Volume:262
Issue / Number:2
Start Page:215
End Page:223
Copyright:Copyright © 2009 Elsevier Inc. All rights reserved.
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:In this study we combine density-functional theory (DFT) calculations on oxygen core excitations in vanadia-silica model clusters with in situ X-ray absorption fine structure (NEXAFS) measurements near the oxygen K-edge of vanadia model catalysts supported by silica SBA-15 in order to analyze structural details of the vanadia species. The silica support is found to contribute to the NEXAFS spectrum in an energy range well above that of the vanadium oxide units allowing a clear separation between the corresponding contributions. Further, differently coordinated oxygen which is characteristic for particular vanadia species, monomeric or non-monomeric, can be identified in the theoretical spectra consistent with the oxygen K-edge NEXAFS measurements. The comparison of the theoretical and experimental NEXAFS spectra provides clear evidence that under in situ conditions different molecular vanadia species, in particular non-monomeric VxOy, exist at the catalyst surface and the exclusive presence of monomeric vanadia groups can be ruled out. The present analysis goes beyond earlier work applying vibrational spectroscopy to the present systems where, as a result of extended vibrational coupling, a separation between vanadia, silica, and interface contributions was less successful.
Free Keywords:Vanadia catalysts; SBA-15 silica; NEXAFS; DFT; Cluster models
External Publication Status:published
Document Type:Article
Communicated by:Robert Schlögl
Affiliations:Fritz-Haber-Institut/Theory
Fritz-Haber-Institut/Inorganic Chemistry/Electronic Structure and Adsorption / Metals
Fritz-Haber-Institut/Inorganic Chemistry/Inorganic Chemistry
External Affiliations:Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Petersenstr. 20, 64287 Darmstadt, Germany

Institut für Chemie, Humboldt-Universität zu Berlin, Unter den Linden 6, 10099 Berlin, Germany
Identifiers:URL:http://dx.doi.org/10.1016/j.jcat.2008.12.013 [only for subscriber]
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