Tailoring surface morphology on anatase TiO2 supported Au nanoclusters: implications for O2 activation

Strong interaction between the support surface and metal clusters activates the adsorbed molecules at the metal cluster-support interface. Using plane-wave DFT calculations, we precisely model the interface between anatase TiO₂ and small Au nanoclusters. Our study focusses on the adsorption and activation of oxygen molecules on anatase TiO₂, considering the influence of oxygen vacancies and steps on the surface. We find that the plane (101) and the stepped (103) surface do not support O₂ activation, but the presence of oxygen vacancies results in strong adsorption and O-O bond length dilation. Modifying the TiO₂ surface with supported small Au_n nanoclusters (n = 3 - 5) also significantly enhances O₂ adsorption and stretches the O-O bond. We observe that manipulating the cluster orientation through discrete rotations results in improved O₂ adsorption and promotes charge transfer from the surface to the molecule. We propose that the orientation of the supported cluster may be manipulated by getting the cluster to adsorb at the step-edge of (103) TiO₂. This results in activated O₂ at the cluster-support interface, with a peroxide-ranged bond length and a low barrier for dissociation. Our modeling demonstrates a straightforward means of exploiting the interface morphology for O₂ activation under low precious metal loading, which has important implications for electrocatalytic oxidation reactions and the rational design of supported catalysts.