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Application of AXAFS Spectroscopy to Transition‐Metal Oxides: Influence of the Nearest and Next Nearest Neighbour Shells in Vanadium Oxides
Author(s) -
Keller Daphne E.,
Weckhuysen Bert M.,
Koningsberger Diek C.
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200601128
Subject(s) - vanadium , vanadium oxide , valence (chemistry) , oxide , chemistry , analytical chemistry (journal) , oxidation state , metal , transition metal , spectroscopy , materials science , inorganic chemistry , crystallography , catalysis , physics , biochemistry , organic chemistry , chromatography , quantum mechanics
The influence of changes in coordination number, interatomic distances, and oxidation state on the intensity and centroid position of the Fourier transform (FT) of the atomic X‐ray absorption fine structure (AXAFS) peak of vanadium oxide bulk model compounds and alumina‐supported vanadium oxide clusters has been investigated. Using Na 3 VO 4 and V 2 O 5 as model compounds, it has been shown that the nearest neighbour shells have a pronounced influence on the AXAFS intensity; specifically, a 40 % decrease in intensity was observed between these two compounds. Secondly, the influence of partial reduction of the vanadium oxide species has been determined; this led to a 50 % decrease in the AXAFS intensity and to an increase in the centroid position. Furthermore, the influence of the vanadium oxide loading has been assessed. A non‐linear relationship between the vanadium oxide loading and the AXAFS intensity has been found, indicating that the AXAFS intensity is sensitive to the formation of VOV bridging bonds between the vanadium VO 4 clusters. The results show that AXAFS can be used to probe the relative energy level of the vanadium valence orbitals.