Consecutive Oxidation of Three H2 Molecules by a Gold-Vanadium Oxide Cluster Cation AuVO4 +

Abstract

Time-of-flight mass spectrometry experiments demonstrated that laser ablation generated and mass selected gold-vanadium heteronuclear oxide cluster AuVO4 + can oxidize three H2 molecules consecutively in an ion trap reactor. Quantum chemistry calculations were employed to reveal the elementary steps involved in the consecutive H2 oxidation. The positively charged gold in AuVO4 + functions as the active site to capture H2 and split the H–H bond in collaboration with the terminal lattice oxygen O2−, during the process of which the superoxide species O2 •− in AuVO4 + is activated and then dissociated to supply enough oxygen sites for the subsequent H2 oxidation. After the oxidation of three H2 molecules, the Au–O bond in AuVO4 + is converted to Au–V bond in product AuVO+ that is inert towards H2. In contast, cluster AuNbO4 + that is structurally related to AuVO4 + can oxdize only one H2 molecule. The origin of the different reactivities between two clusters was explored and the importance of different central metal in H2 oxidation was emphasized.