Vibrational spectra of alumina- and silica-supported vanadia revisited: An experimental and theoretical model catalyst study

Oxide-supported vanadia particles were prepared via evaporation of vanadium metal in an oxygen ambient. As support oxides, we have employed thin, well-ordered alumina and silica films grown on top of NiAl(110) and Mo(112) surfaces. According to our analysis, the vanadia particles exhibit very similar morphology on both supports but differ in the extent of particle-support interactions. It is shown that these differences in the vanadia-support interface region strongly affect the CO adsorption behavior of the particles. The measured vibrational spectra of the model systems are interpreted on the basis of DFT calculations for model compounds and surface models for both the vanadia/silica and the vanadia/alumina system. The combined information is then compared with Raman spectra of real catalytic materials such as vanadia supported over δ-Al₂O₃ and mesoporous SiO ₂ (MCM-41) taken at different laser wavelengths. A consistent interpretation is developed, which shows that the accepted interpretation of vibrational spectra from vanadia catalysts must be revised.