Zhao, Lingyan
(2024)
Computational Studies of Multistep Homogeneous and Heterogeneous Electrochemical Processes.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Catalysis plays a crucial role in industrial chemical processes by increasing reaction rates and improving selectivity and efficiencies. Electrochemical processes can further drive chemical reactions via applied potentials that change the chemical potential of transferring electrons. Under especially complex reaction environments, reaction mechanisms can be challenging to understand, and both homogeneous and heterogeneous reaction pathways can be in play. This work outlines progress in understanding how to elucidate electrocatalytic processes with the end goal of computationally designing idealized catalysts. We first computationally studied homogeneous electrochemical CO2 reduction reaction mechanisms in acetonitrile involving transition metal compounds that lack “non-innocent'” ligands (e.g. bipyridine ligands) that are typically assumed to be necessary. We used Kohn-Sham density functional theory (DFT) with continuum solvation methods to analyze the reaction pathways. After having a baseline understanding of computational tools for studying homogeneous reaction mechanisms, we then investigated heterogeneous electrochemical ozone production (EOP) processes on nickel and antimony doped SnO2 electrode catalysts (NATO). EOP is intriguing as a potentially sustainable method for generating powerful chemical oxidants and disinfectants, but little is presently known about its fundamental catalytic reaction mechanisms that would be needed for improved engineering of EOP electrocatalysts. We used DFT to investigate the thermodynamic feasibility of ozone-producing pathways to better rationalize how and why dopants would influence EOP catalysis. In consort with experimental results, we indicate that EOP is very complex and occurs via several pathways, including non-catalytic corrosion. In summary, we showed that computational modeling can provide insights to better rationalize how and why NATO can catalyze EOP, why the mechanism would likely be different on NATO than other electrodes such as PbO2. We find that EOP adsorbates are significantly stabilized by explicit hydrogen bonding that arises from dissociated co-adsorbed water molecules. Since these interactions are essential to a computational catalysis model that is thermodynamically consistent with experimental observations, it shows the critical importance of developing new computational tools to interrogate electrochemical reaction mechanisms with greater computational efficiency and accuracy.
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| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
|
| Date: |
3 June 2024 |
| Date Type: |
Publication |
| Defense Date: |
6 December 2023 |
| Approval Date: |
3 June 2024 |
| Submission Date: |
19 December 2023 |
| Access Restriction: |
2 year -- Restrict access to University of Pittsburgh for a period of 2 years. |
| Number of Pages: |
118 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Chemical Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
ozone, electrocatalysis |
| Date Deposited: |
03 Jun 2024 14:35 |
| Last Modified: |
03 Jun 2024 14:35 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/45727 |
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