CBE Doctoral Dissertation Defense: “Investigation of Thin-film Cerium-based Oxides and Single Atom Catalysts Prepared by Atomic Layer Deposition” (Kai Shen)

Abstract:
Metal oxides play a critical role in heterogeneous catalysis, acting as active catalysts in a wide range of reactions from dehydrogenation to selective and complete oxidation. However, many catalytically active metal oxides suffer from low surface areas in their bulk form, particularly after high-temperature calcination. This thesis focuses on cerium-based oxides due to their exceptional catalytic properties, particularly in oxygen storage and release. By synthesizing these materials as supported thin films on high surface area γ-Al2O3, we demonstrate that CeFeOx, CeMnOx, and CeVOx thin films not only retain high surface areas under elevated temperatures but also exhibit unique properties compared to their bulk counterparts, including differences in lattice structure and redox behavior. When employed as a support for precious metals like Pt, the choice of reducing or oxidizing pretreatment significantly impacts catalytic activity, as it modulates the interaction between the support and metal. Furthermore, we extended the ALD technique to the synthesis of single-atom catalysts. We invented a novel method, Diluted Atomic Layer Deposition (DALD), to fabricate single-atom catalysts with precisely tunable weight loadings. DALD involves using a mixture of metal precursors and non-metallic ligands (e.g., Pt(acac)2 and Hacac) in controlled ratios. We demonstrated the successful deposition of Ir, Rh, and Pt onto γ-Al2O3, achieving weight loadings ranging from 4 wt% down to as low as 0.04 wt%, with corresponding metal particle sizes ranging from ~2 nm down to isolated single atoms.

Zoom Information:
Meeting ID: 397 149 8817
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