Water-Promoted O2 Dissociation on Small-Sized Anionic Gold Clusters

Although thermodynamically O-2 favors dissociative adsorption over molecular adsorption on small-sized anionic gold clusters (except Au2), O-2 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 O-2 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 O-2 to dissociative adsorption can be significantly lowered with the involvement of a H2O molecule. Once the O-2 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 O-2, which suggests an alternative way to exploit catalytic capability of gold clusters for oxidation applications.