Abstract
The aim of the present project is to systematically quantify and improve the durability of the PEM FC including the following three PEM FC variants: LT PEM FC, DMFC, and HT PEM FC. Different factors influencing dissolution properties of noble metal catalyst platinum and platinum-ruthenium alloy has been studied. The dissolution was found to increase by increasing the CV cycle upper potential limit, number of potential cycles, solution acidity, oxygen partial pressure, involvement of chloride, and temperature. Ruthenium was found to deteriorate ten (10) times faster than platinum catalyst; and carbon supported catalyst (Pt: 20%, Ru: up to 100%) deteriorate ten (10) times faster than non-supported catalyst (Pt: 2%, Ru: 30%) at the same condition. Loss of sulphonic acid groups and fluoride from perfluorinated sulfonic acid membrane was confirmed by different techniques, which locally leads to loss of acidity, and consequently enhances dissolution of noble metal catalyst. Degradation of Nafion ionomer in the electrode was enhanced by noble metal catalyst and the thermal decomposition properties has synergetic effect with carbon degradation. Hydrophobicity of GDL and electrode on GDL were found to degrade e.g. radical attack, oxidation, and physical wear out. The very top micro surface structure turned out to be
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Grahl-Madsen, L;
Odgaard, M;
Munksgaard Nielsen, R;
[1]
Li, Q;
Jensen, Jens Oluf;
[2]
Andersen, Shuang Ma;
Speder, J;
Skou, E
[3]
- IRD Fuel Cell A/S, Svendborg (Denmark)
- Technical Univ. of Denmark, Dept. of Chemistry, Kgs. Lyngby (Denmark)
- Syddansk Univ. (SDU), Odense (Denmark)
Citation Formats
Grahl-Madsen, L, Odgaard, M, Munksgaard Nielsen, R, Li, Q, Jensen, Jens Oluf, Andersen, Shuang Ma, Speder, J, and Skou, E.
Quantify and improve PEM fuel cell durability. Final report.
Denmark: N. p.,
2010.
Web.
Grahl-Madsen, L, Odgaard, M, Munksgaard Nielsen, R, Li, Q, Jensen, Jens Oluf, Andersen, Shuang Ma, Speder, J, & Skou, E.
Quantify and improve PEM fuel cell durability. Final report.
Denmark.
Grahl-Madsen, L, Odgaard, M, Munksgaard Nielsen, R, Li, Q, Jensen, Jens Oluf, Andersen, Shuang Ma, Speder, J, and Skou, E.
2010.
"Quantify and improve PEM fuel cell durability. Final report."
Denmark.
@misc{etde_1000227,
title = {Quantify and improve PEM fuel cell durability. Final report}
author = {Grahl-Madsen, L, Odgaard, M, Munksgaard Nielsen, R, Li, Q, Jensen, Jens Oluf, Andersen, Shuang Ma, Speder, J, and Skou, E}
abstractNote = {The aim of the present project is to systematically quantify and improve the durability of the PEM FC including the following three PEM FC variants: LT PEM FC, DMFC, and HT PEM FC. Different factors influencing dissolution properties of noble metal catalyst platinum and platinum-ruthenium alloy has been studied. The dissolution was found to increase by increasing the CV cycle upper potential limit, number of potential cycles, solution acidity, oxygen partial pressure, involvement of chloride, and temperature. Ruthenium was found to deteriorate ten (10) times faster than platinum catalyst; and carbon supported catalyst (Pt: 20%, Ru: up to 100%) deteriorate ten (10) times faster than non-supported catalyst (Pt: 2%, Ru: 30%) at the same condition. Loss of sulphonic acid groups and fluoride from perfluorinated sulfonic acid membrane was confirmed by different techniques, which locally leads to loss of acidity, and consequently enhances dissolution of noble metal catalyst. Degradation of Nafion ionomer in the electrode was enhanced by noble metal catalyst and the thermal decomposition properties has synergetic effect with carbon degradation. Hydrophobicity of GDL and electrode on GDL were found to degrade e.g. radical attack, oxidation, and physical wear out. The very top micro surface structure turned out to be responsible for wetting property after chemical ageing. Optimal catalyst and ionomer ratio is also reflected in contact angle value, which can be understood in terms of catalyst/carbon - ionomer affinity and layered structure. Long-term tested and 'virgin' LT PEM MEAs have been characterised with respect to SEM, TEM, EDS, and XRD. Both failed and well-functioning MEAs have been characterised. The Post Mortem analysis has shown and quantified degradation mechanisms like catalyst growth and carbon corrosion. Furthermore, the effect of fuel starvation was shown by pronounced Ru-catalyst band within the membrane. The catalyst coarsening observed after approx 4,000 hours of operation correspond to a loss of catalytic active area of 58% for the anode and 69% for the cathode respectively, and the MEA can be expected to perform equivalent to MEAs with less than half the catalyst loating. DMFC durability tests were carried out on both Nafion and Hydrocarbon membrane based MEAs using different electrode designs. Several single DMFC cells and stacks have been tested up to 3,000 hours. The degradation rates found for both single cells and stacks were in the range between 10-90 muV/hours per cell, depending on the MEA configuration. Certain performance losses incurred by the cell during the steady-state operation were recovered, fully or in part, after the regular OCV hold. Regeneration of the Pt-catalyst particles include electro-reduction of the surface PtO that gradually forms over time, surface electro-oxidation of adsorbed poisons (namely CO formed from methanol crossover), and chemical reduction of PtO and/or PtOH via crossover methanol. The HT PEM FC results indicate that a degradation rate of approx 5 muV/h for HT PEM FC can be expected under continuous operation with hydrogen and air at 150-160 C, corresponding to a lifetime of 12,000 hours before 10% performance loss. This lifetime is somewhat shorter than aimed at in the national Danish HT PEM Road map (2009: 20,000 h), but it is in this context important to remember the limited knowledge on HT PEM lifetime at the time of the roadmap definition in 2008. The accelerated durability test with potential cycling showed significant catalyst degradation, primarily due to the corrosion of carbon supports, which triggers the platinum sintering/agglomeration. Modified catalyst supports in form of graphite or carbon nanotubes improve the catalyst and therefore the PBI cell durability. (LN)}
place = {Denmark}
year = {2010}
month = {Jul}
}
title = {Quantify and improve PEM fuel cell durability. Final report}
author = {Grahl-Madsen, L, Odgaard, M, Munksgaard Nielsen, R, Li, Q, Jensen, Jens Oluf, Andersen, Shuang Ma, Speder, J, and Skou, E}
abstractNote = {The aim of the present project is to systematically quantify and improve the durability of the PEM FC including the following three PEM FC variants: LT PEM FC, DMFC, and HT PEM FC. Different factors influencing dissolution properties of noble metal catalyst platinum and platinum-ruthenium alloy has been studied. The dissolution was found to increase by increasing the CV cycle upper potential limit, number of potential cycles, solution acidity, oxygen partial pressure, involvement of chloride, and temperature. Ruthenium was found to deteriorate ten (10) times faster than platinum catalyst; and carbon supported catalyst (Pt: 20%, Ru: up to 100%) deteriorate ten (10) times faster than non-supported catalyst (Pt: 2%, Ru: 30%) at the same condition. Loss of sulphonic acid groups and fluoride from perfluorinated sulfonic acid membrane was confirmed by different techniques, which locally leads to loss of acidity, and consequently enhances dissolution of noble metal catalyst. Degradation of Nafion ionomer in the electrode was enhanced by noble metal catalyst and the thermal decomposition properties has synergetic effect with carbon degradation. Hydrophobicity of GDL and electrode on GDL were found to degrade e.g. radical attack, oxidation, and physical wear out. The very top micro surface structure turned out to be responsible for wetting property after chemical ageing. Optimal catalyst and ionomer ratio is also reflected in contact angle value, which can be understood in terms of catalyst/carbon - ionomer affinity and layered structure. Long-term tested and 'virgin' LT PEM MEAs have been characterised with respect to SEM, TEM, EDS, and XRD. Both failed and well-functioning MEAs have been characterised. The Post Mortem analysis has shown and quantified degradation mechanisms like catalyst growth and carbon corrosion. Furthermore, the effect of fuel starvation was shown by pronounced Ru-catalyst band within the membrane. The catalyst coarsening observed after approx 4,000 hours of operation correspond to a loss of catalytic active area of 58% for the anode and 69% for the cathode respectively, and the MEA can be expected to perform equivalent to MEAs with less than half the catalyst loating. DMFC durability tests were carried out on both Nafion and Hydrocarbon membrane based MEAs using different electrode designs. Several single DMFC cells and stacks have been tested up to 3,000 hours. The degradation rates found for both single cells and stacks were in the range between 10-90 muV/hours per cell, depending on the MEA configuration. Certain performance losses incurred by the cell during the steady-state operation were recovered, fully or in part, after the regular OCV hold. Regeneration of the Pt-catalyst particles include electro-reduction of the surface PtO that gradually forms over time, surface electro-oxidation of adsorbed poisons (namely CO formed from methanol crossover), and chemical reduction of PtO and/or PtOH via crossover methanol. The HT PEM FC results indicate that a degradation rate of approx 5 muV/h for HT PEM FC can be expected under continuous operation with hydrogen and air at 150-160 C, corresponding to a lifetime of 12,000 hours before 10% performance loss. This lifetime is somewhat shorter than aimed at in the national Danish HT PEM Road map (2009: 20,000 h), but it is in this context important to remember the limited knowledge on HT PEM lifetime at the time of the roadmap definition in 2008. The accelerated durability test with potential cycling showed significant catalyst degradation, primarily due to the corrosion of carbon supports, which triggers the platinum sintering/agglomeration. Modified catalyst supports in form of graphite or carbon nanotubes improve the catalyst and therefore the PBI cell durability. (LN)}
place = {Denmark}
year = {2010}
month = {Jul}
}