A new model for the molecular structure of supported vanadium oxide catalysts

Raman spectroscopy experiments found the VO stretching frequency for the supported VO4 species to decrease with increasing catalyst temperature. Calculations on the vibrational frequencies of several models using density functional theory show that a consistent description of the experimental data can be obtained if we assume that the VO4 species are anchored to the oxidic surface by one V–O bond only, in contrast to the traditional pyramidal model, which assumes three V–Osupport bonds and one VO. The proposed VO3 structure points away from the surface and consists of one VO unit and an active oxygen ‘molecule’ loosely bound to the vanadium atom, a peroxide species.