Studies of size-selected iridium, gold, and palladium clusters supported on metal oxide surfaces

This dissertation describes the investigation of catalytic reactivity of size-selected iridium clusters on hydrazine decomposition, water effects on gold clusters sintering, oxidation of size-selected palladium clusters supported by alumina thin film, and CO oxidation catalyzed by palladium clusters over rutile titania surface. Chapter 1 is a brief introduction to the model catalysts, size dependence of catalytic reaction, the properties of supports for catalysts, and an overview of experimental methods in our lab.;For the study of hydrazine decomposition, a design of a chemically inert, ultra-high vacuum compatible, pulsed gas inlet system is described in Chapter 2. An investigation of hydrazine decomposition on size selected iridium clusters, Irn+ (n = 1 ∼ 15), prepared by size-selected cluster ion beam deposition on Al2O3/NiAl (110) surface is presented in Chapter 3. Our experimental results show that the catalytic activity of hydrazine decomposition is strongly dependent on deposited iridium cluster size. In Chapter 4, water dissociation and its effects on thermal stability of gold clusters on TiO2 (110) support are investigated, and we found that water results in more facile agglomeration of the initially dispersed Au atoms, compared to Au deposited on vacuum-annealed TiO2. In Chapters 5 and 6, palladium clusters Pdn + (n = 1 ∼ 20) supported on Al2O3/NiAl (110) and TiO2 (110) substrates are studied, respectively. The oxidation of palladium clusters and CO oxidation catalyzed by the supported catalysts are found to be size dependent, and clearly correlated with palladium core level electron binding energy.