Date of Award

2021

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy in Chemistry (PhD)

Administrative Home Department

Department of Chemistry

Advisor 1

Kathryn A. Perrine

Committee Member 1

Loredana Valenzano-Slough

Committee Member 2

Rudy L. Luck

Committee Member 3

Daisuke Minakata

Abstract

A surface science approach is vital to manufacture earth-abundant catalysts with high reactivity and selectivity and to understand the fundamental chemical and physical driving forces on the surface of these materials. In order to grow next generation heterogeneous catalysts, it is desirable to control the structure, composition, and activity of the catalyst by using a bottom-up surface chemical approach. Area selective deposition (ASD) consists of conformally growing the catalyst from active sites, through surface functionalization. We investigated the surface functionalization and morphological changes of highly oriented pyrolytic graphite (HOPG) from two different wet chemical oxidation methodologies: acid etching using hydrochloric acid (HCl) and nitric acid (HNO3). The HOPG surface was exposed to atomic layer deposition (ALD) cycles of Al2O3 (aluminum oxide): different nanostructures were observed on the two different acid-etched functionalized surfaces. The results suggest that understanding both the topography and the functional group (active site) is vital for designing next-generation heterogeneous catalysts using ASD.

Iron-based materials play a vital role, as not only earth-abundant catalysts, but also in the mineral cycle, aquatic environments, atmospheric particulate dust, and in soil as minerals. The Haber-Bosch process uses nitrogen (N2) and hydrogen (H2) over iron surfaces to produce ammonia (NH3) at high pressures (100-200 atm) and high temperatures (400-500ºC). We investigated the rate-limiting step, the dissociation of N2, on a Fe3O4(001) surface, to determine the chemical changes near ambient pressures. Iron surfaces are readily available in the environment where they are subjected to reduction and oxidation and undergo corrosion. Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) was used to measure the gas phase redox process on magnetite, Fe3O4(001), and hematite, α-Fe2O3(0001), common iron oxide polymorphs. Additionally, we investigated the role of cations from two chloride electrolytes, NaCl and CaCl2, that influence the surface corrosion of iron. The initial stages of corrosion were monitored in situ and the resulting iron-minerals upon air oxidation were characterized. These results provide insight into chemical adsorption and redox reactions, which can assist in unravelling surface chemical, catalytic and corrosion mechanisms under reaction conditions.

Available for download on Tuesday, April 19, 2022

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