Full Text Available
Note: Clicking the button above will open the full text document at the original institutional repository in a new window.
Ti3C2Tx as an Advanced Support Material for Polymer Electrolyte Fuel Cell Catalysts to Facilitate the Oxygen Reduction Reaction
Polymer electrolyte fuel cell's (PEFC's) have the potential to offer a leading energy conversion technology. These fuel cells make use of hydrogen and oxygen and by means of a chemical reaction, electricity, heat and liquid water are produced. In 2015 the Department of Energy (DoE) of the United Sta...
Saved in:
| Main Author: | |
|---|---|
| Other Authors: | |
| Format: | Thesis |
| Language: | English |
| Published: |
Department of Chemical Engineering
2023
|
| Subjects: | |
| Tags: |
No Tags, Be the first to tag this record!
|
| _version_ | 1867613322974593024 |
|---|---|
| access_status_str | Open Access |
| author | America, Tyler Daniel |
| author2 | Rampai, Tokoloho |
| author_browse | America, Tyler Daniel Rampai, Tokoloho |
| author_facet | Rampai, Tokoloho America, Tyler Daniel |
| author_sort | America, Tyler Daniel |
| collection | Thesis |
| description | Polymer electrolyte fuel cell's (PEFC's) have the potential to offer a leading energy conversion technology. These fuel cells make use of hydrogen and oxygen and by means of a chemical reaction, electricity, heat and liquid water are produced. In 2015 the Department of Energy (DoE) of the United States declared a 5000-hour lifetime target for transport applicable fuel cells. With current technological limitation, the achieved lifespan is, however, restricted to only 1700-hours. An assessment to find a more active but primarily more durable support for the oxygen reduction reaction (ORR) in a PEFC than the currently employed carbonaceous support was therefore undertaken. A MXene, Ti3AlC2 was selected for assessment based on its theoretically suitable electrical and thermal conductivities, as well as its possession of among the strongest resistance to oxidation of the many different MAX phases. The synthesis of high (>50 m2 g -1 ), specific surface area, delaminated Ti3C2Tx flakes was attempted first with mild in-situ HF conditions. While this method could both etch and delaminate flakes in a single stage, because the flake size remained large and unchanged, the specific surface area was not seen to increase to the outlined requirements. To synthesize Ti3C2Tx flakes with a high specific surface area, HF etching was therefore employed. In this report, 0.5 g of 400-mesh Ti3AlC2 flakes synthesized by hot pressing were etched in 10 ml of 48 wt % HF for 24 hours at 30 °C. After micronizing for 10 minutes and probe sonicating in solution for a further 40 minutes, high specific surface area (86 m2 g -1 ), delaminated Ti3C2Tx flakes were attained. Using metal organic chemical deposition, well dispersed 2- 5 nm platinum particles were successfully deposited onto the support material. Initial electrochemical performance evaluations indicated a lack of conductivity which restricted electron transport and therefore limited catalyst activity. This was determined to be the result of more defective flakes and by correlation, an increase in interfaces leading to increased resistance. With the incorporation of carbon to the catalyst material to synthesize a hybrid electrode, a positive result confirming ORR activity was attained. While the electrochemical surface area (ECAS) was less than half of that of Pt/C (80 vs 28 m2 g -1 ), it confirmed where the synthesis constraints lie. In review of the durability results, it was found that trapped intermediates between high specific surface area MXene sheets not only restricts access to catalytic sites but are further protonated and reduced to form hydrogen peroxide which causes irreversible damage the PEFC's catalyst membrane. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/37009 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:34:17.944Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2023 |
| publishDateRange | 2023 |
| publishDateSort | 2023 |
| publisher | Department of Chemical Engineering |
| publisherStr | Department of Chemical Engineering |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/37009 Ti3C2Tx as an Advanced Support Material for Polymer Electrolyte Fuel Cell Catalysts to Facilitate the Oxygen Reduction Reaction America, Tyler Daniel Rampai, Tokoloho Levecque, Pieter Chemical Engineering Polymer electrolyte fuel cell's (PEFC's) have the potential to offer a leading energy conversion technology. These fuel cells make use of hydrogen and oxygen and by means of a chemical reaction, electricity, heat and liquid water are produced. In 2015 the Department of Energy (DoE) of the United States declared a 5000-hour lifetime target for transport applicable fuel cells. With current technological limitation, the achieved lifespan is, however, restricted to only 1700-hours. An assessment to find a more active but primarily more durable support for the oxygen reduction reaction (ORR) in a PEFC than the currently employed carbonaceous support was therefore undertaken. A MXene, Ti3AlC2 was selected for assessment based on its theoretically suitable electrical and thermal conductivities, as well as its possession of among the strongest resistance to oxidation of the many different MAX phases. The synthesis of high (>50 m2 g -1 ), specific surface area, delaminated Ti3C2Tx flakes was attempted first with mild in-situ HF conditions. While this method could both etch and delaminate flakes in a single stage, because the flake size remained large and unchanged, the specific surface area was not seen to increase to the outlined requirements. To synthesize Ti3C2Tx flakes with a high specific surface area, HF etching was therefore employed. In this report, 0.5 g of 400-mesh Ti3AlC2 flakes synthesized by hot pressing were etched in 10 ml of 48 wt % HF for 24 hours at 30 °C. After micronizing for 10 minutes and probe sonicating in solution for a further 40 minutes, high specific surface area (86 m2 g -1 ), delaminated Ti3C2Tx flakes were attained. Using metal organic chemical deposition, well dispersed 2- 5 nm platinum particles were successfully deposited onto the support material. Initial electrochemical performance evaluations indicated a lack of conductivity which restricted electron transport and therefore limited catalyst activity. This was determined to be the result of more defective flakes and by correlation, an increase in interfaces leading to increased resistance. With the incorporation of carbon to the catalyst material to synthesize a hybrid electrode, a positive result confirming ORR activity was attained. While the electrochemical surface area (ECAS) was less than half of that of Pt/C (80 vs 28 m2 g -1 ), it confirmed where the synthesis constraints lie. In review of the durability results, it was found that trapped intermediates between high specific surface area MXene sheets not only restricts access to catalytic sites but are further protonated and reduced to form hydrogen peroxide which causes irreversible damage the PEFC's catalyst membrane. 2023-02-23T09:28:34Z 2023-02-23T09:28:34Z 2022 2023-02-20T12:11:02Z Master Thesis Masters MSc http://hdl.handle.net/11427/37009 eng application/pdf Department of Chemical Engineering Faculty of Engineering and the Built Environment |
| spellingShingle | Chemical Engineering America, Tyler Daniel Ti3C2Tx as an Advanced Support Material for Polymer Electrolyte Fuel Cell Catalysts to Facilitate the Oxygen Reduction Reaction |
| thesis_degree_str | Master's |
| title | Ti3C2Tx as an Advanced Support Material for Polymer Electrolyte Fuel Cell Catalysts to Facilitate the Oxygen Reduction Reaction |
| title_full | Ti3C2Tx as an Advanced Support Material for Polymer Electrolyte Fuel Cell Catalysts to Facilitate the Oxygen Reduction Reaction |
| title_fullStr | Ti3C2Tx as an Advanced Support Material for Polymer Electrolyte Fuel Cell Catalysts to Facilitate the Oxygen Reduction Reaction |
| title_full_unstemmed | Ti3C2Tx as an Advanced Support Material for Polymer Electrolyte Fuel Cell Catalysts to Facilitate the Oxygen Reduction Reaction |
| title_short | Ti3C2Tx as an Advanced Support Material for Polymer Electrolyte Fuel Cell Catalysts to Facilitate the Oxygen Reduction Reaction |
| title_sort | ti3c2tx as an advanced support material for polymer electrolyte fuel cell catalysts to facilitate the oxygen reduction reaction |
| topic | Chemical Engineering |
| url | http://hdl.handle.net/11427/37009 |
| work_keys_str_mv | AT americatylerdaniel ti3c2txasanadvancedsupportmaterialforpolymerelectrolytefuelcellcatalyststofacilitatetheoxygenreductionreaction |