Generation of Hydroxyl Radicals in the Reaction of Dihydrogen with AuNbO₄ ⁺ Cluster Cations

A molecular-level insight into the nature of reactive oxygen species involved in dihydrogen (H₂) dissociation is of great importance to understand gold catalysis. In this study, laser ablation generated and mass-selected AuNbO₄ ⁺ oxide cluster cations could dissociate H₂ in an ion-trap reactor. The reaction has been characterized by time-of-flight mass spectrometric experiments and density functional calculations. The lowest energy isomer of AuNbO₄ ⁺ contains two lattice oxygen (O²⁻) and one superoxide (O₂ ^.−) species. The gold atom anchors the H₂ molecule in the first step and then delivers one hydrogen atom to the O²⁻ ion in H₂ dissociation. At the same time, O₂ ^.− is reduced into a peroxide unit that can accept the second hydrogen atom of H₂ with the generation of a hydroxyl radical as the main product. In this study, the important roles of the O₂ ^.− unit in the dissociation of H₂ have been identified.