Date of this Version
Zhou, Yunyun (2015) Nanostructured Cerium Oxide Based Catalysts: Synthesis, Physical Properties, and Catalytic Performance (Doctoral dissertation)
Cerium oxide is an extensively used industrial catalyst with applications as diverse as catalysts for automobile exhaust, petroleum cracking and organic chemicals synthesis. The catalytic activity of cerium oxide is dependent upon its structural properties, especially the oxygen vacancy defects. While recent advances in characterization techniques have dramatically improved our understanding of cerium oxide functionality, many atomic features in cerium oxide contributing to the overall catalytic reactivity are not yet well-understood. This dissertation focuses on the structural studies of catalytically active cerium oxides with different compositions, phases and morphologies, and their utilizations to establish fundamental understandings of cerium oxide based catalyst systems.
Defect sites in reducible metal oxide nanomaterials such as cerium oxide play an important role in their catalytic activities. In this dissertation, nanostructured cerium oxides with different densities of oxygen vacancy defects have been synthesized. High density of oxygen vacancy defects has been shown to promote the dispersion, activity and self-regeneration ability of supported noble metal nanoparticles.
Strong interactions between metal particles and metal oxide supports induce changes in the electronic structures of metal particles, such as oxidation state and valence band structure. Two studies on the strong metal-support interactions, the alteration of oxidation states of supported palladium particles under different redox environments and s-d orbital hybridization of supported gold nanoclusters, are presented in this dissertation.
The morphology, size and shape of cerium oxide profoundly affect its reaction performance. Controlling the morphology of nanostructured catalyst allows selective exposure of reactive facets which improve catalytic activity, selectivity, and stability of the catalysts. This dissertation presents a study of the morphological effect of difference cerium oxide support structures on the catalytic activity of supported platinum particles towards alcohol electrooxidation.
Cerium oxide demonstrates catalytic activity of generating reactive oxygen species towards Fenton-like reaction with hydrogen peroxide. This dissertation presents a study of singlet oxygen generation, one of the reactive oxygen species, through hydrogen peroxide decomposition. Chemical trap reagent of singlet oxygen has been demonstrated to exhibit photobleaching under photo-irradiation. The study also includes investigation of kinetics of singlet oxygen generation and elucidation of reaction order with respect to hydrogen peroxide.
Advisor: Chin Li “Barry” Cheung