| dc.contributor.author | Bonakdarpour, Arman. | en_US |
| dc.date.accessioned | 2014-10-21T12:33:57Z | |
| dc.date.available | 2007 | |
| dc.date.issued | 2007 | en_US |
| dc.identifier.other | AAINR31495 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/54957 | |
| dc.description | This thesis presents measurements of the stability and activities of Pt-based oxygen reduction reaction (ORR) electrocatalysts for proton exchange membrane fuel cells (PEMFC). Because more than 70% of electrochemical losses originate from the cathodic reduction of oxygen, research on ORR catalysts remains very active. | en_US |
| dc.description | Numerous combinatorial libraries of Pt1-xMx (M = Fe, Ni, Mn; 0 ≤ x ≤ 1) and Pt1-x-yMxMy ' (M, M' = Co, Ni, Mn, Fe) were prepared by magnetron sputtering using high surface area nano-structured thin film (NSTF) supports as substrates. The libraries were studied for the corrosion stability of the transition metal elements by acid leaching experiments. The results show that after exposing these libraries to 0.5M H2SO4 (or HClO4) at 80°C for several days, significant amounts of transition metals leach off. When the transition metal content was about 60% or less mostly surface leaching occurred and for more than 60% surface and bulk leaching were observed. The composition of these libraries after acid treatment was very close to the electrocatalysts tested in hydrogen fuel cells, thus showing that acid treatment can mimic the fuel cell environment very well. Alloys of Pt-Ta, on the other hand, showed no dissolution of Ta. However, the presence of more than 10% Ta in the alloy, significantly reduces the ORR activity. | en_US |
| dc.description | The rotating ring-disk electrode technique was used to measure the ORR activity of sputtered Pt1-xCox (0 < x < 0.5) films. After heat treatment a 1.7x gain in the specific current densities were observed. There are claims in the literature that very high activities (about 10x) can be achieved by Pt alloys such as Pt-Co with similar preparation methods. Poor experimental setups are most likely the sources of these observations. | en_US |
| dc.description | High surface area Pt and Pt-Co-Mn catalysts, sputtered onto NSTF supports were studied using the RRDE technique. The Pt-Co-Mn alloy showed a kinetic gain of about 20 mV over Pt for ORR. This is in agreement with the FC results. | en_US |
| dc.description | The impact of catalyst loading in RRDE experiments on the production of H2O2 during ORR, is discussed. It was found that lower loadings of both Pt-based and non-noble metal catalysts generate more H2O2 during the oxygen reduction reaction. These observations have important implications for both fundamental studies and applications. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 2007. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Physics, Condensed Matter. | en_US |
| dc.subject | Energy. | en_US |
| dc.title | A combinatorial study of platinum-based oxygen reduction electrocatalysts for hydrogen fuel cells. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
