Effect of PTFE content in gas diffusion layer based on Nafion®/PTFE membrane for low humidity proton exchange membrane fuel cell

Tsai, Jie Cheng; Lin, Chien Kung

doi:10.1016/j.jtice.2011.05.008

Cited by 35 publications

(14 citation statements)

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“…The negative aspects of this approach are the reduced pore space for the gas transport by lower porosity, lower electrical conductivity and liquid water accumulation in the electrode due to the increased entry pressure into the GDL. However, different groups have shown that the cell performance and stability increases by adding up to 20 wt% PTFE into the GDL [5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Modeling the Liquid Water Transport in the Gas Diffusion Layer for Polymer Electrolyte Membrane Fuel Cells Using a Water Path Network

Alink

Gerteisen

2013

Energies

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In order to model the liquid water transport in the porous materials used in polymer electrolyte membrane (PEM) fuel cells, the pore network models are often applied. The presented model is a novel approach to further develop these models towards a percolation model that is based on the fiber structure rather than the pore structure. The developed algorithm determines the stable liquid water paths in the gas diffusion layer (GDL) structure and the transitions from the paths to the subsequent paths. The obtained water path network represents the basis for the calculation of the percolation process with low calculation efforts. A good agreement with experimental capillary pressure-saturation curves and synchrotron liquid water visualization data from other literature sources is found. The oxygen diffusivity for the GDL with liquid water saturation at breakthrough reveals that the porosity is not a crucial factor for the limiting current density. An algorithm for condensation is included into the model, which shows that condensing water is redirecting the water path in the GDL, leading to an improved oxygen diffusion by a decreased breakthrough pressure and changed saturation distribution at breakthrough.

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Section: Introductionmentioning

confidence: 99%

Modeling the Liquid Water Transport in the Gas Diffusion Layer for Polymer Electrolyte Membrane Fuel Cells Using a Water Path Network

Alink

Gerteisen

2013

Energies

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“…Therefore, the structure of the GDL, fibre geometry and porosity [6], as well as applied compression [7] have been under investigation to understand how to optimise gas and water transport without hindering electron transport. Engineering of the material has been of particular focus, as its structure and PTFE content directly affect the water management and fuel cell performance [3,[8][9][10]. The GDL is usually composed of carbon fibres around 5-10 m in diameter, coated with a PTFE/carbon medium 'microporous' layer [11].…”

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confidence: 99%

“…The GDL is usually composed of carbon fibres around 5-10 m in diameter, coated with a PTFE/carbon medium 'microporous' layer [11]. The most suitable concentration of PTFE within the GDL [8,12,13] and MPL [14] is of particular focus, as it regulates water accumulation and polymer electrolyte humidification [13].To understand and optimize the transport phenomena through these porous materials, it is necessary to study the microstructural characteristics using high resolution techniques. 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.…”

mentioning

confidence: 99%

“…Unlike SEM, computed tomography can be used to capture the internal 3D structure, and through image processing techniques, can help determine the porosity, pore size and tortuosity. Thermogravimetric analysis (TGA) has been used to quantify PTFE content [8,27,28] in the gas diffusion layer. The pyrolysis process provides the mass of PTFE in the entire sample analysed, whereas SEM / EDS provides an indication of the surface PTFE content.…”

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confidence: 99%

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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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Multi‐Scale Imaging of Polymer Electrolyte Fuel Cells using X‐ray Micro‐ and Nano‐Computed Tomography, Transmission Electron Microscopy and Helium‐Ion Microscopy

et al. 2019

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Multi‐length scale imaging of polymer electrolyte fuel cell (PEFC) membrane electrode assembly (MEA) materials is a powerful tool for studying, understanding and furthering improvements in materials engineering, performance and durability. A hot pressed MEA has been imaged using X‐ray micro‐ and nano‐computed tomography (CT), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and recently developed helium‐ion microscopy (HeIM). X‐ray nano‐CT captures a volume containing all of the relevant fuel cell interfaces, from the carbon fiber of the gas diffusion layer (GDL) to the Nafion membrane with a field‐of‐view of 5 µm and a pixel size of 64 nm. Features identified include linear marks on the carbon fiber surface, agglomerates of carbon nanoparticles in the microporous layer (MPL), and intrusion of the catalyst layer material into the Nafion membrane during the hot‐pressing process. HeIM has enabled imaging of a large area of MEA from tens of micrometers to sub‐nanometers pixel resolution without any sample preparation, and has captured similar features to X‐ray micro‐CT and nano‐CT. Furthermore, at its highest resolution, the platinum and carbon catalyst nanoparticles can be distinguished at the surface of the catalyst layer, overcoming the limitations of SEM and TEM.

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Effect of PTFE content in gas diffusion layer based on Nafion®/PTFE membrane for low humidity proton exchange membrane fuel cell

Cited by 35 publications

References 20 publications

Modeling the Liquid Water Transport in the Gas Diffusion Layer for Polymer Electrolyte Membrane Fuel Cells Using a Water Path Network

Modeling the Liquid Water Transport in the Gas Diffusion Layer for Polymer Electrolyte Membrane Fuel Cells Using a Water Path Network

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

Multi‐Scale Imaging of Polymer Electrolyte Fuel Cells using X‐ray Micro‐ and Nano‐Computed Tomography, Transmission Electron Microscopy and Helium‐Ion Microscopy

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