Electronic Structure Controls Reactivity of Size-Selected Pd Clusters Adsorbed on TiO 2 Surfaces

Cluster Electronics and Catalysis Many practical catalysts consist of small metal clusters on oxide supports, and the activity of these clusters usually varies with their size. In order to sort out some of the competing effects that lead to such variations, Kaden et al. (p. 826 ) size-selected palladium clusters (from single atoms to clusters up to 25 atoms) and deposited them on a crystal face of the rutile phase of titanium dioxide. X-ray photoemission studies and temperature-programmed reaction measurements showed that the activity of these model catalysts for CO oxidation was related to the electronic energy, which was reflected in the Pd 3d electron binding energy. Ion-scattering studies showed that the clusters formed flat single- or double-layer islands.