Characterization of MEA degradation for an open air cathode PEM fuel cell

Silva, R.A.; Hashimoto, T.; Thompson, G. E.; Rangel, C. M.

doi:10.1016/j.ijhydene.2011.12.110

Cited by 63 publications

(17 citation statements)

References 47 publications

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“…Recent research [27] indicates that the CCL experiences a significant thinning upon being exposed to degradation protocols. It appears however, that few studies exist that investigate the dependence of the stability of PEM-cathodes on initial CCL thickness.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Catalyst Layer Thickness on the Performance and Degradation of PEM Fuel Cell Cathodes with Constant Catalyst Loading

Darab

Barnett

Lindbergh

et al. 2017

Electrochimica Acta

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Three catalytic layers containing Pt nanoparticles supported on high surface area carbon of different Pt loading but with the same total amount of platinum and therefore of different thickness were employed as cathode catalytic layers (CCLs) in a PEM fuel cell. The layers were subjected to a degradation protocol with an upper potential limit of 1.5 V. Upon exposure to the degradation protocol particle size increased, the electrochemical areas (ECAs) of the catalysts decreased, the catalytic layers became thinner, and the average pore size decreased, indicating both carbon and Pt corrosion. The relative decrease in the ECA was approximately the same for all three layers and was therefore approximately independent of CCL thickness. For all samples the reaction order with respect to oxygen was one half and the samples showed doubling of the slope of the potential vs. log current curve (dE/d log i) at high current densities. This indicates that kinetics control the potential at low currents and kinetics and proton migration (ohmic drops in the catalytic layer) at high. However, the degradation protocol also introduced limitations due to oxygen diffusion in the agglomerates. This led to a quadrupling of the dE/d log i-slope in 13% oxygen in the samples with the highest catalyst area per volume. For the sample with the lowest catalyst area per volume this slope increased by a factor of six in 13% oxygen, indicating that the local current density exceeded that required for the Tafel slope of the oxygen-reduction reaction (ORR) to double.

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Section: Introductionmentioning

confidence: 99%

The Influence of Catalyst Layer Thickness on the Performance and Degradation of PEM Fuel Cell Cathodes with Constant Catalyst Loading

Darab

Barnett

Lindbergh

et al. 2017

Electrochimica Acta

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“…4e) and CCM-3 ( Fig. 4f) because of large amount of gas generation in the catalyst layers during water electrolysis and nonuniformity of compression force between the land and under the channel [14]. However, there were no gaps in the cocrystallized CCM-1 before (Fig.…”

Section: Resultsmentioning

confidence: 97%

“…Compared with the gas diffusion electrode, the CCM has been demonstrated to have lower catalyst loading, thinner and much more hydrophilic catalyst layers [11]. However, the catalyst layers of the CCM are prone to peel off from the membrane for the following reasons: (1) the different swelling degrees between membrane and catalyst layers in water, (2) large amount of gas generation in catalyst layers during water electrolysis, and (3) nonuniformity of compression force between the land and under the channel [14,15]. In addition, the complete hydrophilicity of catalyst layers of CCM makes against the gas transmission, thus decreases the utilization ratio of the catalysts [9].…”

Section: Introductionmentioning

confidence: 99%

A cocrystallized catalyst-coated membrane with high performance for solid polymer electrolyte water electrolysis

Wang

Shao

et al. 2013

Journal of Power Sources

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“…Until recently, the main technique used to determine the GDL structure was scanning electron microscopy (SEM), frequently coupled with energy dispersive X-ray spectroscopy (EDS) analysis. SEM is useful in obtaining surface structural data, layer thickness, 'smoothness' of different interfaces, PTFE bonding, and fibre orientation, but fails to reveal the porosity and internal structure [5,6,[15][16][17][18][19][20][21][22]. Micro and nano X-ray computed tomography (CT) are non-destructive methods that can achieve sufficiently high resolution for the imaging of carbon fibres, which typically have diameters between 5 and 10 m, and they have been increasingly used to characterise GDLs [7,19,[23][24][25][26].…”

Section: Gas Diffusion Layersmentioning

confidence: 99%

Effect of gas diffusion layer properties on water distribution across air-cooled, open-cathode polymer electrolyte fuel cells: A combined ex-situ X-ray tomography and in-operando neutron imaging study

Meyer

Ashton

Boillat

et al. 2016

Electrochimica Acta

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2 Highlights First description of in-plane water distribution using neutron imaging in an aircooled, open-cathode fuel cell. High water content identified under cathode land area, whereas anode water content is relatively homogeneous. Water distribution in anode GDL directly linked to dispersion of PTFE. Anode GDL composition shown to affect water content and distribution in cathode. Combined X-ray computed tomography, SEM/EDS and TGA used to characterise GDL structure and composition. AbstractIn-situ diagnostic techniques provide a means of understanding the internal workings of fuel cells under normal operating conditions so that improved designs and operating regimes can be identified. Here, an approach is used which combines exsitu characterisation of two anode gas diffusion / microporous layers (GDL-A and GDL-B) with X-ray computed tomography and in-situ analysis using neutron imaging of operating fuel cells. The combination of TGA, SEM and X-ray computed tomography reveals that GDL-A has a thin microporous layer with 26 % PTFE covering a thick diffusion layer composed of 'spaghetti' shaped fibres. GDL-B is covered by two microporous media (29 % and 6.5 % PTFE) penetrating deep within the linear fibre network. The neutron imaging reveals two pathways for water management underneath the cooling channel, either diffusing through the cathode GDL to the active channels, or diffusing through the membrane and towards the 3 anode. Here, these two behaviours are directly affected by the anode gas diffusion PTFE content and porosity. KeywordsGas diffusion layer; air-cooled open-cathode; X-ray computed tomography; neutron imaging; water management. IntroductionPolymer electrolyte fuel cells (PEFC) fuelled with hydrogen are among the most promising energy conversion technologies for a broad range of applications, including portable, stationary and automotive power delivery. However, understanding the cell water management is crucial for performance optimisation.Flooding impedes reactant transport (water mainly concentrating at the cathode) and reduces the surface area of the catalyst, causing significant if not catastrophic decay in cell performance, and dehydration can lead to cracks and irreversible damage [1][2][3]. The gas diffusion layer (GDL) provides a pathway for electron transport, ensures even reactant delivery and helps water management within each cell. The water balance between flooding and membrane dehydration is a function of the GDL's structure, porosity and PTFE (hydrophobic) content. Here, two commercial GDLs with microporous layers are characterised ex-situ by capturing the design and structure via X-ray computed tomography (CT), along with its polytetrafluoroethylene (PTFE) / carbon distribution via SEM/EDS analysis and thermogravimetric analysis (TGA); in-situ 'visualisation' of the water distribution in the in-plane orientation was performed using neutron radiography. These techniques can be correlated with one another to gain new insights into the water management role of the GDL in fuel c...

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Characterization of MEA degradation for an open air cathode PEM fuel cell

Cited by 63 publications

References 47 publications

The Influence of Catalyst Layer Thickness on the Performance and Degradation of PEM Fuel Cell Cathodes with Constant Catalyst Loading

The Influence of Catalyst Layer Thickness on the Performance and Degradation of PEM Fuel Cell Cathodes with Constant Catalyst Loading

A cocrystallized catalyst-coated membrane with high performance for solid polymer electrolyte water electrolysis

Effect of gas diffusion layer properties on water distribution across air-cooled, open-cathode polymer electrolyte fuel cells: A combined ex-situ X-ray tomography and in-operando neutron imaging study

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