Inducing wetting morphologies and increased reactivities of small Au clusters on doped oxide supports

Au nanoparticles are promising catalysts for industrially important reactions. Their catalytic activity is known to depend on their charge state and morphology. Using density functional theory calculations, we have studied how the induced charge and dimensionality of small Au clusters can be tuned by doping the oxide support that they are deposited on. We have investigated Au clusters of sizes n = 1, 2, 3, and 20 on Al-doped MgO and Mo-doped CaO. We show that substitutionally doping the oxide support with an electron donor changes the cluster morphology from an upright and/or three-dimensional geometry to a flat geometry. This structural wetting transition results in an increase in the negative charge induced on the cluster and a consequent lowering in the dissociation barrier for the O₂ atoms adsorbed on the cluster. We find that the nature of Mo and Al dopants differs: only for the former is it true that the charge state of the dopant atoms depends on the presence or absence of Au nanoparticles and their size.