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Dissertation
Single-site catalysts on transitional surfaces: characterizing single-atom behavior on thinly oxidized Cu(111)
Washington State University
Doctor of Philosophy (PhD), Washington State University
2022
DOI:
https://doi.org/10.7273/000005065
Abstract
Catalysts are exposed to non-equilibrium chemical environments that cause surface composition and structural heterogeneity. This dissertation investigates the metal-support interactions that drive the behavior of precious metal single-site catalysts on a transient Cu-based support between fully oxidized Cu2O and fully reduced Cu by characterizing the chemistry and structures of the surface species on the "29" oxide model. The "29" oxide model is an epitaxially grown CuxO film on Cu(111), providing a well-defined, Cu2O(111)-like surface for single-atom support. It is demonstrated that the factors which determine the stability and chemistry of the surface species on the "29" oxide are distinct from atomically dispersed metals supported on bulk oxide and Cu surfaces. Three important aspects were studied via Density Functional Theory: (1) the active sites for CO oxidation, (2) the role of the oxide layer toward the stabilization of single atoms, and (3) the sensitivity of the activity of precious metal single-atoms toward its local coordinate environments. We validated our model studies with surface science experiments provided by the Sykes group.
Our results indicate that a higher heterogeneity and mobility of Rh surface species on the "29" oxide led to a higher reaction complexity with CO in comparison to that with Pt species. The migration of single atoms is driven by their ability to form and break bonds with the oxide overlayer. The effect of the oxide overlayer on single atom segregation on Cu(111) is twofold, depending on the initial position of the single atom. Overall, the factors which drive atom stability on thin oxides contrast with those on bulk oxides. The reactivity of single-site Pt was investigated in the setting of a Cu2O(111) environment to further understand the sensitivity of its activity on copper oxide structures. Atomic changes within its environment can drastically change the significance of Pt toward increasing CO oxidation activity. This work serves as a baseline to further develop models that will reflect the metal-support interactions of atoms supported on Cu-based structures within the oxidation state gap between Cu2O and Cu, important for the rational design of single-site catalysts.
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Details
- Title
- Single-site catalysts on transitional surfaces
- Creators
- Nisa Zakia Zahra Ulumuddin
- Contributors
- Jean-Sabin McEwen (Advisor)Charles Sykes (Committee Member)Yong Wang (Committee Member)Aurora Clark (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of Chemical Engineering and Bioengineering
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 289
- Identifiers
- 99901019640201842
- Language
- English
- Resource Type
- Dissertation