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

VO 2 (V 2 O 5 ) n CH 3 OH + ( n = 1–3) complexes are generated from the interactions of pregenerated VO 2 (V 2 O 5 ) n + clusters with CH 3 OH 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 V 3 O 7 CH 3 OH + are CH 2 O and V 3 O 7 H 2 +, whereas those of V 5 O 12 CH 3 OH + and V 7 O 17 CH 3 OH + are CH 3 OH and the corresponding V x O y + ( x, y = 5,12 and 7,17). Collision-induced dissociation and density functional theory/RRKM calculations suggest that CH 3 OH is dissociatively adsorbed on V 3 O 7 +, whereas it is nondissociatively adsorbed on V 5 O 12 + and V 7 O 17 + . This study suggests that the thermal dissociation of CH 3 OH to CH 3 O is the prerequisite for its photo-oxidation into CH 2 O, which may shed light on the photochemistry of methanol over transition metal oxide surfaces.