Extending in situ XAS of PEM fuel cells to more realistic conditions
Extending in situ XAS of PEM fuel cells to more realistic conditions
One of the challenges facing the further development of fuel cells is an understanding of the catalyst structure and in turn, how this relates to performance. In an effort to advance research in this area, a miniature PEM fuel cell has been designed to enable in situ X-ray Absorption Spectroscopy (XAS) investigations of catalysts using fluorescence detection. The development of the cell is described, in particular the modification required for elevated temperature operation and humidification of the feed gasses.
The electrocatalytic activity of a series of carbon supported PtRu anode catalysts towards a electro-oxidation of CO and oxidation of methanol were studied. It was found that in both cases, the PtRu 1:1 catalyst gave the highest performance. Particle segregation was observed in the platinum rich catalysts with a ruthenium rich core and a platinum rich surface relative to the bulk composition. Further XAS studies of the PtRu 1:1 catalyst were carried out in a PEM fuel cell. Operating conditions were found to have a significant impact on catalyst utilisation. The Pt component was readily reduced by hydrogen in the fuel, while the Ru component was only fully reduced under conditions of good gas flow and electrochemical contact. Upon introduction of reformate, no evidence of carbon neighbours were observed. This was interpreted in relation to the lack of surface sensitivity of the Extended X-ray Absorption Fine Structure (EXAFS) method.
The activity towards the oxygen reduction reaction was studied using carbon supported PtCr, PtCo and PtTi cathode catalysts. XAS studies revealed that the Pt-Pt distance, intrinsically linked to the Pt electronic properties, gave the best indication of oxygen reduction activity. No correlation was observed between the number of Pt-O coordination numbers and catalyst activity. This implies that under realistic fuel cell conditions, site blocking by oxide formation is not as significant as first thought.
University of Southampton
Wiltshire, Richard John Kenneth
f98966c5-c193-42da-bbcf-0e4faf3242b9
2005
Wiltshire, Richard John Kenneth
f98966c5-c193-42da-bbcf-0e4faf3242b9
Wiltshire, Richard John Kenneth
(2005)
Extending in situ XAS of PEM fuel cells to more realistic conditions.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
One of the challenges facing the further development of fuel cells is an understanding of the catalyst structure and in turn, how this relates to performance. In an effort to advance research in this area, a miniature PEM fuel cell has been designed to enable in situ X-ray Absorption Spectroscopy (XAS) investigations of catalysts using fluorescence detection. The development of the cell is described, in particular the modification required for elevated temperature operation and humidification of the feed gasses.
The electrocatalytic activity of a series of carbon supported PtRu anode catalysts towards a electro-oxidation of CO and oxidation of methanol were studied. It was found that in both cases, the PtRu 1:1 catalyst gave the highest performance. Particle segregation was observed in the platinum rich catalysts with a ruthenium rich core and a platinum rich surface relative to the bulk composition. Further XAS studies of the PtRu 1:1 catalyst were carried out in a PEM fuel cell. Operating conditions were found to have a significant impact on catalyst utilisation. The Pt component was readily reduced by hydrogen in the fuel, while the Ru component was only fully reduced under conditions of good gas flow and electrochemical contact. Upon introduction of reformate, no evidence of carbon neighbours were observed. This was interpreted in relation to the lack of surface sensitivity of the Extended X-ray Absorption Fine Structure (EXAFS) method.
The activity towards the oxygen reduction reaction was studied using carbon supported PtCr, PtCo and PtTi cathode catalysts. XAS studies revealed that the Pt-Pt distance, intrinsically linked to the Pt electronic properties, gave the best indication of oxygen reduction activity. No correlation was observed between the number of Pt-O coordination numbers and catalyst activity. This implies that under realistic fuel cell conditions, site blocking by oxide formation is not as significant as first thought.
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Published date: 2005
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Local EPrints ID: 465670
URI: http://eprints.soton.ac.uk/id/eprint/465670
PURE UUID: 89059ed2-e6d9-4590-9b06-ac5c003f0845
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Date deposited: 05 Jul 2022 02:31
Last modified: 16 Mar 2024 20:18
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Author:
Richard John Kenneth Wiltshire
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