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Fabrication of PtNi and PtV near-surface alloys as improved catalysts for proton exchange membrane hydrogen fuel cells
This study concerns the characterization of platinum nickel (PtNi) and platinum vanadium (PtV) near-surface alloys (NSAs) for use as improved catalysts in proton exchange membrane hydrogen fuel cells. The need for this study arose in order to further understand the principles behind the predicted ca...
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| Format: | Thesis |
| Language: | English |
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Centre for Materials Engineering
2017
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| _version_ | 1867613233230118912 |
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| access_status_str | Open Access |
| author | Leary, Clinton Derek |
| author2 | Lang, Candace Irene |
| author_browse | Lang, Candace Irene Leary, Clinton Derek |
| author_facet | Lang, Candace Irene Leary, Clinton Derek |
| author_sort | Leary, Clinton Derek |
| collection | Thesis |
| description | This study concerns the characterization of platinum nickel (PtNi) and platinum vanadium (PtV) near-surface alloys (NSAs) for use as improved catalysts in proton exchange membrane hydrogen fuel cells. The need for this study arose in order to further understand the principles behind the predicted catalytic properties of NSAs, to fabricate them and to characterize them experimentally. Two groups of NSAs were fabricated, namely PtNi and PtV. Pt was used as the parent metal while Ni and V were used as the solute/near surface constituents. Within these groups of pt with Ni or V, variations in coating thickness and heat treatments were used to attempt to fabricate the NSA structure. Surface profile analysis was carried out using profilometry and light microscopy. These techniques showed that surfaces were not always of a 100% mirror finish and that deposited coatings were not stable and were prone to peeling especially with coatings of greater than one layer. Elemental analysis was performed by employing energydispersive x-ray spectroscopy (SEM-EDS), proton induced x-ray emission (PIXE) and Rutherford backscattering spectrometry (RBS). These techniques helped verify the presence of the thin deposited coatings whilst also highlighting the presence of contaminants in the form of iron, manganese and chromium. Tafel Plot analysis was used to gather electrochemical data for the NSAs. In this regard, the hydrogen reduction (evolution) reaction was analyzed with the exchange current density extracted experimentally therefrom. This technique confirmed that Pt is indeed a superior catalyst, especially compared to pure Ni and V. It showed that ebeam deposition did not create coated systems which were suitable for Tafel analysis. It also illustrated that deaeration via nitrogen gas was not always effective with trace oxygen sometimes being present in the purge gas, resulting in contaminant oxygen reduction distorting the electrochemical results. Ultimately, electron-beam deposition proved to be inefficient in fabricating stable coatings for catalysis, with the coatings possibly not being adequately thin to mimic the NSA structure. This, coupled with trace oxygen reduction, prevented effective analysis of NSA catalytic properties. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/24283 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:32:52.713Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2017 |
| publishDateRange | 2017 |
| publishDateSort | 2017 |
| publisher | Centre for Materials Engineering |
| publisherStr | Centre for Materials Engineering |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/24283 Fabrication of PtNi and PtV near-surface alloys as improved catalysts for proton exchange membrane hydrogen fuel cells Leary, Clinton Derek Lang, Candace Irene Materials Engineering This study concerns the characterization of platinum nickel (PtNi) and platinum vanadium (PtV) near-surface alloys (NSAs) for use as improved catalysts in proton exchange membrane hydrogen fuel cells. The need for this study arose in order to further understand the principles behind the predicted catalytic properties of NSAs, to fabricate them and to characterize them experimentally. Two groups of NSAs were fabricated, namely PtNi and PtV. Pt was used as the parent metal while Ni and V were used as the solute/near surface constituents. Within these groups of pt with Ni or V, variations in coating thickness and heat treatments were used to attempt to fabricate the NSA structure. Surface profile analysis was carried out using profilometry and light microscopy. These techniques showed that surfaces were not always of a 100% mirror finish and that deposited coatings were not stable and were prone to peeling especially with coatings of greater than one layer. Elemental analysis was performed by employing energydispersive x-ray spectroscopy (SEM-EDS), proton induced x-ray emission (PIXE) and Rutherford backscattering spectrometry (RBS). These techniques helped verify the presence of the thin deposited coatings whilst also highlighting the presence of contaminants in the form of iron, manganese and chromium. Tafel Plot analysis was used to gather electrochemical data for the NSAs. In this regard, the hydrogen reduction (evolution) reaction was analyzed with the exchange current density extracted experimentally therefrom. This technique confirmed that Pt is indeed a superior catalyst, especially compared to pure Ni and V. It showed that ebeam deposition did not create coated systems which were suitable for Tafel analysis. It also illustrated that deaeration via nitrogen gas was not always effective with trace oxygen sometimes being present in the purge gas, resulting in contaminant oxygen reduction distorting the electrochemical results. Ultimately, electron-beam deposition proved to be inefficient in fabricating stable coatings for catalysis, with the coatings possibly not being adequately thin to mimic the NSA structure. This, coupled with trace oxygen reduction, prevented effective analysis of NSA catalytic properties. 2017-05-16T07:33:23Z 2017-05-16T07:33:23Z 2015 Master Thesis Masters MSc (Eng) http://hdl.handle.net/11427/24283 eng application/pdf Centre for Materials Engineering Faculty of Engineering and the Built Environment University of Cape Town |
| spellingShingle | Materials Engineering Leary, Clinton Derek Fabrication of PtNi and PtV near-surface alloys as improved catalysts for proton exchange membrane hydrogen fuel cells |
| thesis_degree_str | Master's |
| title | Fabrication of PtNi and PtV near-surface alloys as improved catalysts for proton exchange membrane hydrogen fuel cells |
| title_full | Fabrication of PtNi and PtV near-surface alloys as improved catalysts for proton exchange membrane hydrogen fuel cells |
| title_fullStr | Fabrication of PtNi and PtV near-surface alloys as improved catalysts for proton exchange membrane hydrogen fuel cells |
| title_full_unstemmed | Fabrication of PtNi and PtV near-surface alloys as improved catalysts for proton exchange membrane hydrogen fuel cells |
| title_short | Fabrication of PtNi and PtV near-surface alloys as improved catalysts for proton exchange membrane hydrogen fuel cells |
| title_sort | fabrication of ptni and ptv near surface alloys as improved catalysts for proton exchange membrane hydrogen fuel cells |
| topic | Materials Engineering |
| url | http://hdl.handle.net/11427/24283 |
| work_keys_str_mv | AT learyclintonderek fabricationofptniandptvnearsurfacealloysasimprovedcatalystsforprotonexchangemembranehydrogenfuelcells |