In this thesis five iron phthalocyanines (FePc’s), four of which having different
electron withdrawing or electron donating substituents, were evaluated as 0₂
reduction reaction (ORR) catalysts. The experimental approach simulated a
PEM fuel cell environment using both ex-situ electrochemical techniques and in
situ fuel cell testing.
The kinetic ORR parameters for the FePc species each adsorbed on a
pyrolytic graphite WE were evaluated at four temperatures (20, 40, 60, 80°C) in a
novel half cell using cyclic voltammetry (CV) and rotating disk electrode (RDE)
voltammetry. Kinetic ORR parameters included the overall ORR electron transfer
number, reaction rate constants, cathodic Tafel slopes, electron transfer numbers
in the rate determining step, and electron transfer co-efficients. An increase in
temperature from 60°C to 80°C showed a decrease in the overall electron
transfer number observed for all four substituted FePc species. A mechanism
was also proposed based on the experimental results.
The RDE results were confirmed using a rotating ring disk electrode (RRDE).
From these RRDE results, the fraction of H₂0₂ produced (XH₂₀₂) at the disk
during the ORR was calculated. These XH₂₀₂ values agreed with the overall
ORR electron transfer numbers from the RDE results obtained under the same
conditions.
lron(Il) 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25 — hexadecachioro
29H,31H-phthalocyanine (FePcCI₁₆)was down selected for further investigation as the most stable and active substituted FePc species for the ORR. Both
FePcCl₁₆ and the unsubstituted FePc, were supported on carbon and made into
catalyst inks for carbon fibre paper (CFP) electrode testing, and then evaluated
using CV in the N₂ purged, followed by the air saturated, electrolytes,
respectively.
Finally, MEA’s for fuel cell testing were made using FePc species catalyst ink
cathodes, and commercial Pt/C anodes. The MEA’s were tested using custom
designed and built fuel cell hardware. Open circuit voltages, polarization curves,
and power curves were recorded. Initial results indicated the FePcCI₁₆ MEA’s
showed superior stability, higher open circuit voltages, as well as better
polarization and power curves when compared to the unsubstituted FePc
species.
It was found that FePc species with strongly electron withdrawing
substituents, such as FePcCl₁₆ showed the highest stability and greatest ORR
activity. FePc species, including pyrolized FeNx/C analogues, show much
promise as alternatives to Pt in PEMFC’s, as well as dye sensitized solar cells
(DSSC’s).
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU./5030 |
| Date | 11 1900 |
| Creators | Baker, Ryan Christopher Colin |
| Publisher | University of British Columbia |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | 4800358 bytes, application/pdf |
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