H₂ Oxidation Mediated by Au₁-Doped Vanadium Oxide Cluster Cation AuV₂O₅⁺: A Comparative Study with AuCe₂O₄

To clarify the relationship between the type of the oxide support and the activity of the gold-doped oxide clusters toward H₂ oxidation, a suitable closed-shell system AuV₂O₅⁺ is chosen to have a comparative study with AuCe₂O₄⁺, the first closed-shell cluster that is reactive toward H₂ oxidation. The reaction of AuV₂O₅⁺ with H₂ was characterized by mass spectrometry and density functional theory calculations. The AuV₂O₅⁺ cluster is reactive toward H₂ leading to the major product of V₂O₅H₂⁺ (+ Au), whereas the product of AuV₂O₄⁺ (+ H₂O) is completely absent in the experiment. This is in sharp contrast with the similar reaction system of AuCe₂O₄⁺ with H₂, in which the formation of H₂O was experimentally evidenced. Theoretical calculations revealed that the distinct reaction behaviors between AuV₂O₅⁺ and AuCe₂O₄⁺ can be attributed to the gold-metal bond strength, which plays an important role in anchoring the gold atom. The weaker Au-V bond promotes the evaporation of Au, which has a negative effect on the total oxidation of H₂ to H₂O. This comparative study provides molecular-level mechanisms to understand the important roles of the gold-metal bond in the oxidation of hydrogen molecule over metal oxide supports.