Inhomogeneous Distribution of Polytetrafluorethylene in Gas Diffusion Layers of Polymer Electrolyte Fuel Cells

Froning, Dieter; Reimer, Uwe; Lehnert, Werner

doi:10.1007/s11242-021-01542-0

Cited by 9 publications

(4 citation statements)

References 44 publications

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“…The calculated ranges of the effective conductivities and their comparison to the experimental results suggest an PTFE-fiber arrangement equivalent to an in-series arrangement is more likely. Studies have found that the PTFE also accumulates around the fiber-fiber intersections, 13,49,50 effectively improving the fiber-fiber thermal contact. However, we were limited in the XTM resolution and the fiber-PTFE contrast, which did not allow to resolve and separately segment the two solid phases.…”

Section: Resultsmentioning

confidence: 99%

Conductive Heat Transfer in Partially Saturated Gas Diffusion Layers with Evaporative Cooling

Vanrooij¹,

Magnini²,

Mularczyk³

et al. 2022

J. Electrochem. Soc.

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Heat transport is an important, though often neglected function of gas diffusion layers (GDLs) of polymer electrolyte membrane fuel cells. Thermal conductivity is a key property, especially in partially water saturated GDLs and when the phase change of water is considered, such as required for evaporative cooling applications. Continuum models require effective transport properties as input, which in this work were determined for different types of dry and partially saturated commercial GDLs (Toray 060 and 120, Freudenberg H23). Three-dimensional microstructures and phase distributions were recorded using X-ray tomographic microscopy, digitalized and used in direct pore-level simulations. The governing energy conservation equation was solved in the three phases (gas, liquid, solid) with interfacial heat transfer between the phases to determine the effective thermal conductivity. Correlations for through-plane effective thermal conductivity in the different GDL types as a function of saturation are provided. An energy sink term, accounting for the evaporation of water, was added, enabling a quantification of the effective conductive heat transfer in GDLs with evaporative cooling. The water distribution (clustered or layered) in the GDLs was found to be a key factor for the thermal conduction and evaporative cooling ability.

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Section: Resultsmentioning

confidence: 99%

Conductive Heat Transfer in Partially Saturated Gas Diffusion Layers with Evaporative Cooling

Vanrooij¹,

Magnini²,

Mularczyk³

et al. 2022

J. Electrochem. Soc.

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“…Jeon [ 16 ] and Yang et al [ 17 ] adopted LBM to study the flow of liquid water due to different rib-channel widths and found that the two-phase behavior under the rib was the origin of the difference in fuel cell performance. Scholars have focused on the different wettability of fiber [ 18 ] and non-uniform distribution of PTFE [ 19 , 20 , 21 , 22 , 23 ], and the wettability of GDL has been demonstrated to have a significant effect on water transport. Hao and Cheng [ 18 ] compared highly hydrophobic GDLs with GDLs with nearly neutral wettability and considered wettability to be an important parameter controlling the two-phase behavior within the GDL.…”

Section: Introductionmentioning

confidence: 99%

Effects of Compression and Porosity Gradients on Two-Phase Behavior in Gas Diffusion Layer of Proton Exchange Membrane Fuel Cells

et al. 2023

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Water management within the gas diffusion layer (GDL) plays an important role in the performance of the proton exchange membrane fuel cell (PEMFC) and its reliability. The compression of the gas diffusion layer during fabrication and assembly has a significant impact on the mass transport, and the porosity gradient design of the gas diffusion layer is an essential way to improve water management. In this paper, the two-dimensional lattice Boltzmann method (LBM) is applied to investigate the two-phase behavior in gas diffusion layers with different porosity gradients under compression. Compression results in an increase in flow resistance below the ribs, prompting the appearance of the flow path of liquid water below the channel, and liquid water breaks through to the channel more quickly. GDLs with linear, multilayer, and inverted V-shaped porosity distributions with an overall porosity of 0.78 are generated to evaluate the effect of porosity gradients on the liquid water transport. The liquid water saturation values within the linear and multilayer GDLs are significantly reduced compared to that of the GDL with uniform porosity, but the liquid water within the inverted V-shaped GDL accumulates in the middle region and is more likely to cause flooding.

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“…Polymer electrolyte fuel cells (PEFCs) have gained increasing attention as power sources in automotive, portable, and stationary applications, due to rapid start-ups at low temperatures, quiet operation, high efficiencies, and possible zero emissions [1][2][3][4][5][6][7][8][9][10]. PEFCs are limited by the cost, performance, and durability of the device; as such, optimisation of the cell components is needed to facilitate wider commercialisation [8,[10][11][12]. The gas diffusion media (GDM) is a crucial component in the membrane electrode assembly (MEA) of the PEFC, as it facilitates the transport of reactant gases to the catalyst layer (CL) and has a substantial impact on the efficiency of the cell, as it regulates the heat and water produced because of the electrochemical reaction [6,9].…”

Section: Introductionmentioning

confidence: 99%

Effect of Microporous Layer Ink Homogenisation on the Through-Plane Gas Permeability of PEFC Porous Media

et al. 2023

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The through-plane gas permeability and morphology of PEFC gas diffusion media (GDM) is investigated for different microporous layer (MPL) ink homogenisation techniques (bath sonication and magnetic stirring) for low- (Vulcan XC-72R) and high (Ketjenblack EC-300J)-surface-area carbon powders. The MPL composition is held constant at 80 wt.% carbon powder and 20 wt.% PTFE for a carbon loading of 1.0 mg cm−2. The MPL ink homogenisation time is held constant at two hours for both techniques and increased by one hour for bath sonication to compare with previous investigations. The results show that the through-plane gas permeability of the GDM is approximately doubled using magnetic stirring when compared with bath sonication for MPLs composed of Vulcan XC-72R, with a negligible change in surface morphology between the structures produced from either homogenisation technique. The variation in through-plane gas permeability is almost negligible for MPLs composed of Ketjenblack EC-300J compared with Vulcan XC-72R; however, MPL surface morphology changes considerably with bath sonication, producing smoother, less cracked surfaces compared to the large cracks produced via magnetic stirring for a large-surface-area carbon powder. An MPL ink sonication time of three hours results in a percentage reduction in through-plane gas permeability from the GDL substrate permeability by ~72% for Ketjenblack EC-300J compared to ~47% for two hours.

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Inhomogeneous Distribution of Polytetrafluorethylene in Gas Diffusion Layers of Polymer Electrolyte Fuel Cells

Cited by 9 publications

References 44 publications

Conductive Heat Transfer in Partially Saturated Gas Diffusion Layers with Evaporative Cooling

Conductive Heat Transfer in Partially Saturated Gas Diffusion Layers with Evaporative Cooling

Effects of Compression and Porosity Gradients on Two-Phase Behavior in Gas Diffusion Layer of Proton Exchange Membrane Fuel Cells

Effect of Microporous Layer Ink Homogenisation on the Through-Plane Gas Permeability of PEFC Porous Media

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