Identification of oxygen sites at the V2O5(010) surface by core-level electron spectroscopy: Ab initio cluster studies

Abstract

Vanadium oxide contains differently coordinated oxygen sites which can participate in catalytic oxidation reactions of industrial relevance. For a full understanding of corresponding reaction steps an estimate of the relative importance of these oxygen sites for a given reaction at the surface is required. This may be possible using electron spectroscopy together with theoretical methods. We have performed density functional theory cluster calculations to describe the electronic structure at the V2O5(010) surface which possesses singly, doubly, and triply coordinated oxygen sites, O(1–3). For these sites we have evaluated O 1s core level excitation spectra using the transition state method. The analysis of the spectra based on atom projected densities-of-states of the unoccupied orbitals shows that all spectral features are determined by local V–O bonding. The spectra for different oxygen coordination differ enough to allow discrimination between the oxygen sites. In contrast, differences in the calculated O 1s core ionization potentials depend much less on coordination. A comparison of the theoretical O 1s core level excitation spectra with experimental NEXAFS and ELNES spectra yields rather good agreement and assists the interpretation of the latter. Further, the theoretical IP data are consistent with experimental XPS spectra.