Photoreaction Study of Methanol Adsorption Complexes on VO2(V2O5)n+ (n = 1–3) Clusters at 355 nm

Abstract

VO2(V2O5)nCH3OH+ (n = 1–3) complexes are generated from the interactions of pregenerated VO2(V2O5)n+ clusters with CH3OH in a fast flow reactor. The photoreactions of these three adsorption complexes at 355 nm are characterized by a high-resolution tandem time-of-flight mass spectrometer. The major photoproducts of V3O7CH3OH+ are CH2O and V3O7H2+, whereas those of V5O12CH3OH+ and V7O17CH3OH+ are CH3OH and the corresponding VxOy+ (x, y = 5,12 and 7,17). Collision-induced dissociation and density functional theory/RRKM calculations suggest that CH3OH is dissociatively adsorbed on V3O7+, whereas it is nondissociatively adsorbed on V5O12+ and V7O17+. This study suggests that the thermal dissociation of CH3OH to CH3O is the prerequisite for its photo-oxidation into CH2O, which may shed light on the photochemistry of methanol over transition metal oxide surfaces.