Evolution of the surface species of the V2O5–WO3 catalysts

Vanadia-related species formed as a result of vanadium segregation at the surface of V–W oxide bronze crystallites were investigated. The structures of these species and their transformations induced by oxygen removal and oxygen adsorption were monitored using photoelectron spectroscopy and the FT Raman technique. Assignments of the MeO vibrational bands, based on the results of DFT calculations for model clusters, have been proposed. Two kinds of surface species are dominant depending on the tungsten content: V4+–O–W6+ at low tungsten content and V5+–O–W5+ at higher tungsten concentration.