Catalyst layer design and carbonate management for energy efficient electrochemical CO2 reduction to fuels and chemicals
Abstract/Contents
- Abstract
- Reducing anthropogenic CO2 emissions will be critical for mitigating the harmful effects of climate change on the environment. The ability to cost-effectively capture CO2 from point sources and utilize it as a chemical feedstock would allow several industrial processes to become carbon neutral. CO2 reduction (CO2R) powered by renewable electricity is a promising strategy for converting CO2 into valuable fuels and chemicals such as ethylene, ethanol, propanol, and acetate. To advance this technology for commercial applications, its operational costs must be reduced by improving energy and carbon efficiencies. Unfortunately, performing CO2R at low cell voltages at steady state is extremely challenging. Alkaline electrolytes minimize the cell voltage of CO2R, but CO2 rapidly reacts with OH-- to form (bi)carbonate (HCO3-- and CO32--), which drives the pH to 8 at steady state where the cell voltages are much higher. One approach to avoid (bi)carbonate formation is to use a two-stage electrolysis system, which consists of a CO2R step to generate CO, followed by CO reduction (COR) to multicarbon products in a separate electrolyzer. Solid oxide electrolysis cells can convert CO2 into high-purity CO streams at very high energy efficiency. Moreover, CO reacts with OH-- very slowly, which allows alkaline conditions to be maintained at steady state, thereby enabling low COR cell voltages. Both direct CO2R and the two-step process are being explored, but the energy efficiencies of both systems are still far too low. Improving cathode performance, developing ideas for managing (bi)carbonate formation, and constructing innovative cell designs will be necessary to advance these technologies towards commercialization. In this dissertation, we work towards improving the energy efficiency of CO2R and COR in several ways. We first provide a strategy for lowering the cathode overpotential for COR. We find that using a thick catalyst layer with percolated networks of hydrophobic pores and 5 µm Cu domains enables a high catalyst loading, which reduces cathode overpotentials. Such layers achieve a steady state COR cell voltage of 2.13 V at 200 mA cm--2, which is the lowest reported cell voltage for COR or CO2R at high current density. We then present an approach for mitigating CO2 uptake in direct CO2R by using highly concentrated (bi)carbonate electrolytes. This works towards maintaining alkaline conditions at steady state, which reduces operational cell voltages. Finally, we provide a platform for prototyping flow fields with 3D printing, which will be beneficial for scaling up CO2 and CO electrolyzers. .
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2022; ©2022 |
| Publication date | 2022; 2022 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Rabinowitz, Joshua |
|---|---|
| Degree supervisor | Kanan, Matthew William, 1978- |
| Thesis advisor | Kanan, Matthew William, 1978- |
| Thesis advisor | Burns, Noah |
| Thesis advisor | Chueh, William |
| Degree committee member | Burns, Noah |
| Degree committee member | Chueh, William |
| Associated with | Stanford University, Department of Chemistry |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Joshua Rabinowitz. |
|---|---|
| Note | Submitted to the Department of Chemistry. |
| Thesis | Thesis Ph.D. Stanford University 2022. |
| Location | https://purl.stanford.edu/rv349yq3690 |
Access conditions
- Copyright
- © 2022 by Joshua Rabinowitz
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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