Dissertation
Using electrons to transform negative-value feedstocks to benign or value-added products
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Spring 2022
DOI: 10.17077/etd.006432
Abstract
The electrification of chemical manufacturing or running the chemical manufacturing processes through electrochemical reactions is one of the major milestones for electrochemical engineering. Electrification can result in decreases in energy consumption per capita for these industries through more efficient reaction pathways and is a unique opportunity for green solutions within the industry through the pairing of green energy systems, such as solar and wind, through the removal of petroleum-based feedstocks from some of the processes, and through utilization of negative-value feedstocks, like carbon dioxide and nitrates. Major chemical manufacturing processes that can benefit from research into electrochemical solutions include chlor-alkali, synthesis gas generation, and ammonia production.
In this work, we show three systems in which surface wettability modifications to electrocatalysts directly affect the chemical processes through changes to product formation and reaction efficiency. In Chapter 3 – Surface Wettability Modified Silver Oxygen Reduction Reaction, a hydrophilic sample can produce almost exclusively hydroxide as its product while untreated samples have a near 1:1 mix of hydroxide and peroxide. In Chapter 4 - Surface Wettability Modified Silver CO2 Reduction Reaction, the ratio of hydrogen to carbon monoxide in synthesis gas produced on modified silver electrodes was able to be tuned through controlled wettability modifications resulting in ratios from 1:1 to 4:1. In Chapter 5 - Surface Wettability Modified Copper NO3 Reduction Reaction, the products formed showed unique results on modified copper samples with the suppression of nitrite production on treated samples and increased ammonia production on hydrophilic samples.
In this work, we also preliminarily explored plasmon-assisted electrochemical reactions for carbon dioxide reduction. In Chapter 6 - Collection of Plasmon-Assisted Electrocatalysis Works, we were able to show photoresponses on copper/cuprous nanowires, copper-coated gold nanowires, and gold/silver alloy nanodisks. In our studies with copper/cuprous nanowires, we were able to show nanowire synthesis and a change in product formation from dark electrochemistry and photo-assisted electrochemistry. More experimentation would be needed to verify product formation and to better understand the mechanistic changes made during plasmon-assisted electrocatalysis. In our studies with copper-coated gold nanowires, we were able to show successful deposition of gold nanowires with a UPD deposition of copper on the surface as well as photoresponses on both bare gold and coated gold of similar magnitude. Future work would be needed to verify product and efficiency changes that occur between dark and illuminated electrochemistry for these samples. In our studies with gold/silver alloy nanodisks, we were able to show a photoresponse on the nanodisk samples as prepared as well as a process through which we can dealloy the material through the controlled removal of silver. This will result in a porous gold substrate with controlled amounts of silver to determine how photoresponse is affected by alloy composition and the structure of the material. Future work is needed to test this sample for a value-added-product forming, electrochemical reaction.
Overall, this collection of experimental results has helped to further our understanding of the basics behind electrochemical reactions on surfaces with changes to their wettability, structure, and photoresponses. These understandings, with further engineering and research, could provide some of the building blocks for the electrification of chemical manufacturing and green chemical systems.
Details
- Title: Subtitle
- Using electrons to transform negative-value feedstocks to benign or value-added products
- Creators
- Austin L. McKee
- Contributors
- Syed Mubeen (Advisor)Johna Leddy (Committee Member)C. Allan Guymon (Committee Member)Hongtao Ding (Committee Member)Joe Gomes (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Chemical and Biochemical Engineering
- Date degree season
- Spring 2022
- DOI
- 10.17077/etd.006432
- Publisher
- University of Iowa
- Number of pages
- xvi, 142 pages
- Copyright
- Copyright 2022 Austin L. McKee
- Language
- English
- Description illustrations
- Charts, graphs, tables
- Description bibliographic
- Includes bibliographical references (pages 132-142).
- Public Abstract (ETD)
Electrochemical engineering explores the application of electricity driven chemical reactions. One major goal of electrochemical engineering is to convert most, if not all, chemical industry systems to electrical power from renewable sources. The largest area of focus is converting the chemical reaction process itself into an electrochemical one that uses electricity to make chemical products. There are three main chemical manufacturing industries globally that could benefit from such changes: production of chlorine, synthesis gas, and ammonia.
Electrochemical processes typically need to be done in water to make movement of charged molecules between electrodes easier. Because of this, changing how wet a surface can get by modifying it shows how the interactions between an electrode’s surface and the water change the efficiency of the reactions. Through these modifications, we were able to control product ratios by tuning the water’s attraction to the electrode’s surface.
There is also an electrochemical phenomenon where light energy can be converted into electrical energy for reactions, which is called “plasmon resonance.” Plasmon resonance is when light, which is made up of an electrical and magnetic field, causes movement (resonance) of electrons, which are the driving force in electrochemical reactions. The electron movement allows some energy required for chemical reactions to be provided by light, reducing the amount of extra energy needed for the reaction.
These technologies could provide a major steppingstone into improving the quality of electrochemical processes leading to the adoption of electrically driven chemical synthesis processes.
- Academic Unit
- Chemical and Biochemical Engineering
- Record Identifier
- 9984271354702771
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