Interaction of O2 with Gold Clusters: Molecular and Dissociative Adsorption

Abstract

The interaction of O 2 with charged and neutral gold clusters, Au N - and Au N containing up to eight atoms, investigated through the use of density functional theory with generalized gradient corrections and scalar relativistic pseudopotentials, exhibits a pronounced sensitivity to the cluster size and to its charge state. Molecular adsorption is found to be favorable regardless of the charge state for clusters with N ≤ 3, while dissociative adsorption is favored for larger clusters. The dissociation process involves a significant barrier (1 eV or more), and it is predicted to result in a large structural distortion in the host gold cluster. The interaction energy is largest for the anionic gold clusters where it exhibits an odd−even alternation as a function of the number of gold atoms, with the maxima occurring for Au N O 2 - complexes with even N . The molecular bonding mechanism to these complexes involves charge transfer to the oxygen molecule with a concomitant activation of the O−O bond to a superoxo-like state.