Active role of oxide support during CO oxidation at Au/MgO.

The oxidation of CO at MgO supported gold aggregates is studied by means of density functional theory calculations. In addition to serving as a structural promoter holding the gold particles, the supporting oxide also takes an active role in the bonding and activation of adsorbates bound to the gold. The oxide stabilizes a peroxolike reaction intermediate, CO.O2, and causes steric repulsion to CO. The most reactive site at Au/MgO appears where the gold shelters the MgO thereby creating a cavity where several low-coordinated Au atoms and Mg2+ cations from the substrate can interact simultaneously with an adsorbate.