Catalysis research using model catalysts
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Catalysts are essential for technological advances, because of their indispensable role in chemical and material manufacturing, energy conversion, and pollution control systems. Developing better catalysts is a highly desired goal that is impeded by the complexity of heterogeneous catalysts. This makes it extremely difficult to obtain information regarding active sites and reaction mechanisms, which is critical for improving catalyst design and performance. My research work has led to the understanding of how specific catalytic surface sites affect the performance of catalysts by constructing conceptually simpler planar model catalysts for kinetics and mechanism studies using model surface science tools and batch reaction testing. The work in this dissertation has demonstrated that planar model catalysts are versatile tools to probe reaction mechanisms on industrial catalysts. Supported gold nanoparticles have shown remarkable catalytic activity in a variety of reactions. However, many fundamental aspects of gold catalysts are still unclear, especially about the identity of active sites and oxidizing species. A Au(111) single crystal, the most stable and abundant facet on gold nanoparticles, is utilized to understand the reaction mechanisms of partial oxidation of 2-butanol and allyl alcohol. By controlling oxygen coverage on the surface, 100% selectivity to corresponding ketone and aldehyde, the desirable products, can be achieved. Two model catalysis systems, gold nanoclusters supported on a TiO₂(110) substrate and iron oxide dispersed on a Au(111) surface, were employed to understand the reaction pathways of CO oxidation and probe the role of the oxide/metal interface. The mechanistic and kinetic studies have shown that planar model catalysts are useful tools to probe reactions on industrial catalysts. The mechanistic understanding obtained from model catalyst studies can be used to create better catalysts.