Investigating the Surface Morphology and Stability of Heterogeneous Catalysts Synthesized by Atomic Layer DepositionPublic Deposited
Heterogeneous catalysts play a prominent role in our society, used in applications that range from the production of plastics to the catalytic cracking of crude oil. Industrial catalysts are typically made of mixed metal oxides or nanosized metal particles deposited on high surface area supports. Industrially relevant catalytic materials are complex in composition and morphology, often having different reactions occurring on surface sites, interfaces and defects. Atomic layer deposition can grow highly uniform thin films and nanoparticles, each ALD cycle limited by surface-selective thermodynamically favorable reactions. This atomic control allows the development of catalytic surfaces incremented in morphology (nanoparticle size, pore size) and composition (mixed metals and oxides, tunable surface site density). Atomic layer deposition was used to create series of catalysts with incremental nanoscale differences in morphology, aiming to highlight important factors in catalyst surface chemistry, stability and selectivity. Chapters two and three focus on the characterization of supported palladium nanoparticle catalysts. Through a comparison to alumina dehydration, chapter two investigates the nanoscale porosity of ALD deposited alumina oxide catalyst coatings. Palladium nanoparticles were further investigated on model strontium titinate nanocuboids with well-defined facets. ALD was used to systematically increase palladium loading in order to investigate nucleation and nanoparticle morphology on materials with the same bulk composition, but distinct surface energies. The last three chapters focus on applying ALD to catalytic reactions: synthesizing uniform silica sites for cyclohexanol dehydration, stabilizing plasmonic for catalytic reactions and monitoring alkene epoxidation through in situ spectroscopy. Using atomic layer deposition and informed by fundamental surface science, this research aims to increase the understanding of catalyst morphology, stability and reactivity.