Water-promoted O₂ dissociation on small-sized anionic gold clusters

Although thermodynamically O₂ favors dissociative adsorption over molecular adsorption on small-sized anionic gold clusters (except Au ₂^-), O₂ dissociation is unlikely to proceed under ambient conditions because of the high activation energy barrier (>2.0 eV). Here, we present a systematic theoretical study of reaction pathways for the O₂ dissociation on small-sized anionic gold nanoclusters Au _n^- (n = 1-6) with and without involvement of a water molecule. The density functional theory calculations indicate that the activation barriers from the molecular adsorption state of O₂ to dissociative adsorption can be significantly lowered with the involvement of a H₂O molecule. Once the O₂ dissociates on small-size gold clusters, atomic oxygen is readily available for other reactions, such as the CO oxidation, on the surface of gold clusters. This theoretical study supports previous experimental evidence that H₂O can be used to activate O₂, which suggests an alternative way to exploit catalytic capability of gold clusters for oxidation applications.