(289i) Linking Electronic Structure to Catalytic Activity of Pure and Doped Pd Clusters Deposited On Stoichiometric and Defected Titania Surfaces

Sub-nano clusters of Pd supported on TiO₂ (110) have been shown experimentally to have a catalytic activity toward CO oxidation, which is strongly and nonlinearly dependent on cluster size. Using a range of theoretical methods, including ab initio and DFT+U, and statistical mechanics simulations, we address the electronic structure origin of these observed size-dependent properties. We will address the shape, stability, mobility, and catalytic activity of selected clusters of Pd on stoichiometric and defected titania. Small Pd clusters wet titania, bind preferentially to the stoichiometric part of the surface, and migrate quite easily. The smallest deposited clusters quickly disappear at elevated temperatures through sintering. The catalytic activity is strongly correlated with the ability of clusters to activate, and in some cases dissociate O₂. The chemistry of Pd clusters is found to be effectively orthogonal to that of deposited Au clusters. Based on these observations, we rationally chose to dope deposited Pd clusters with Au for enhanced catalysis. Indeed, our calculations confirm the desired effect on the activity toward CO oxidation.