Studies of size selected gold and iridium cluster catalysts

This dissertation describes the investigation of catalytic reactivity of gold clusters on carbon monoxide oxidation and iridium clusters on hydrazine decomposition using a size selected cluster ion beam deposition. Chapter 1 is a brief introduction to the size selected clusters, the role of support on catalysis and background on a gold catalyst.; An investigation of CO oxidation on size selected gold clusters, Au n+ (n = 1∼7), prepared by size-selected cluster ion beam deposition on a single crystal TiO2(110) surface is presented in Chapter 2. Our experimental results show that the catalytic activity is strongly dependent on deposited cluster size. Chapter 3 describes strong carbon monoxide adsorption on gold atoms or small size particles as deposited at 115K. Oxygen vacancy and gold atom complex formation results in Au binding energy shift and CO desorption while annealing. In Chapter 4, carbon monoxide oxidation, adsorption and thermal stability of gold clusters on alumina support are investigated and compared with gold clusters on TiO2 support. Catalytic oxidation was not observed in gold on alumina catalysts. These results show that the size of the metal cluster and interactions between the support and the metal cluster play an important role in carbon monoxide oxidation.; Hydrazine decomposition on Ir/Al2O3/NiAl(110) is investigated in Chapter 5. N2 formation by direct decomposition and by a dissociation-recombination was observed. The continuous flow experiment results demonstrate that the ammonia production rate depends on the catalyst temperature and that production of ammonia is competitive with production of N2.