Microstructure of Gas Diffusion Layers for PEM Fuel Cells

Parikh, N.; Allen, Jeffrey S.; Yassar, Reza S.

doi:10.1002/fuce.201100014

Cited by 52 publications

(58 citation statements)

References 20 publications

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“…To identify the mean fiber lengths in the inplane direction, images of PTL surface were analyzed to identify the fibers and their orientation with respect to one of the orthogonal axis. First, the distribution of fiber lengths and orientation relative to an orthogonal direction was established using the procedure similar to that described in Parikh et al 30 The projected fiber length in the in-plane direction, f , is found by multiplying the mean fiber length by the cosine of the mean fiber orientation. This projected length characterizes the mean, in-plane length over which heat transfer occurs without a fiber-to-fiber contact.…”

Section: In-plane Effective Thermal Conductivitymentioning

confidence: 99%

Material and Morphological Heat Transfer Properties of Fuel Cell Porous Transport Layers

Konduru

Allen

2017

J. Electrochem. Soc.

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The complex structure of the porous transport layer (PTLs), commonly referred to as gas diffusion layers (GDL), makes direct measurement of thermal transport properties difficult. Typically, effective thermal conductivity values are obtained experimentally and computational models are developed to replicate the measurements. This approach is sufficient for generalized one-dimensional models of fuel cell performance, but is not sufficient to predict reactant maldistribution due to the presence of liquid water in the PTL. Further, the anisotropy in the PTL structure results in dissimilar properties for through-plane and in-plane transport. In this work an analytical model is developed to extract material properties from effective thermal conductivity measurements. The model accounts for the change in the effective thermal conductivity as a function of compression. Geometric changes due to compression are separated from morphological changes using a compression modulation function; the shape of which is indicative of how fiber-to-fiber contact morphology changes with respect to strain. Material and morphological properties are determined using effective thermal conductivity data for three commercial PTLs. The properties also enable prediction of in-plane heat transfer using through-plane empirical data and also provide insight into morphological changes due to compression. A porous transport layer (PTL), more commonly referred to as a gas diffusion layer (GDL), has multiple purposes in a fuel cell including distribution of reactant gases to the catalyst layer, facilitation of product water removal from the catalyst layer, electronic and thermal conduction to/from the catalyst layer, and redistribution of compressive stresses across the membrane electrode assembly (MEA). A typical PTL consists of carbon fibers, either in fibrous or a non-woven morphology, along with binding agents and non-wetting agents such as polytetrafluoroethylene (PTFE). Examples of a non-woven and a fibrous PTL are shown in Figure 1. PTL designation is used herein because the transport phenomena of interest is not restricted to diffusion of reactant gases, but is focused heat transfer.Heat transfer across a dry PTL is primarily due to conduction. When liquid water is present, then additional heat may be transferred from the catalyst layer via evaporation and conduction via the liquid water occupying the void space. Either mode of heat transfer, conduction or evaporation, may be the dominant effect depending upon the operating conditions.1 The location of an evaporation front within a PTL depends upon the temperature and temperature gradient within the PTL. The same can be said for water condensation within the PTL as demonstrated by Caulk and Baker.2 A highly conductive PTL may increase the conduction of heat, but result in widely distributed condensation that can block reactant transport. A less conductive PTL may decrease the conduction of heat, but result in a sharp temperature gradient that generates a thin, uniform layer of water which al...

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Section: In-plane Effective Thermal Conductivitymentioning

confidence: 99%

Material and Morphological Heat Transfer Properties of Fuel Cell Porous Transport Layers

Konduru

Allen

2017

J. Electrochem. Soc.

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“…Poornesh et al [8] found a relationship between the GDL's in-plane mechanical properties and membrane thinning. Parikh et al [9] investigated the relationship between fuel cell efficiency and GDL materials by testing GDL samples from Freudenberg, SGL and Toray. They studied pore size distributions but also size, shape and orientation of the pores.…”

Section: Introductionmentioning

confidence: 99%

3D analysis, modeling and simulation of transport processes in compressed fibrous microstructures, using the Lattice Boltzmann method

Froning

Brinkmann

Reimer

et al. 2013

Electrochimica Acta

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In this paper we combine a stochastic 3D microstructure model of a fiber based gas diffusion layer of polymer electrolyte fuel cells with a Lattice Boltzmann model for fluid transport. We focus on a simple approach of compressing the planar oriented virtual geometry of paper-type gas diffusion layer from Toray. Material parameters -permeability and tortuosity -are calculated from simulation of one phase, one component gas flow in stochastic geometries. We analyze the statistical spread of simulation results on ensembles of the virtual geometry, both uncompressed and compressed. The influence of the compression is discussed with regard to the Kozeny-Carman equation. The effective transport properties calculated from transport simulations in compressed gas diffusion layers agree well with a trend based on the Kozeny-Carman equation.

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“…Parikh et al extracted pore size distribution of SGL, Toray and Freudenberg materials from scanning electron microscopy. 55 An average pore diameter of 31. • , but we assume a higher contact angle of θ = 60…”

Section: Resultsmentioning

confidence: 99%

Advanced Water Management in PEFCs: Diffusion Layers with Patterned Wettability

Forner‐Cuenca

Biesdorf

Lamibrac

et al. 2016

J. Electrochem. Soc.

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In this paper, we present an experimental study on the development of gas diffusion layer (GDL) materials for fuel cells with dedicated water removal pathways generated using radiation induced grafting of hydrophilic compounds onto the hydrophobic polymer coating. The impact of several material parameters was studied: the carbon substrate type, the coating load, the grafted chemical compound and the pattern design (width and separation of the hydrophilic pathways). The corresponding materials were characterized for their capillary pressure characteristic during water imbibition experiments, in which we also evidenced the differences between injection from a narrow distribution channel in the center of the material (and thus strongly relying on lateral transport) and homogeneous injection from one face of the material. All materials parameters were observed to have a significant influence on the water distribution. In particular, the type of substrate has a dramatic impact, with results ranging from a nearly perfect separation of water between hydrophilic and hydrophobic domains for substrates having a narrow pore size distribution to a fully random imbibition of the material for substrates having a broad pore size distribution.

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Microstructure of Gas Diffusion Layers for PEM Fuel Cells

Cited by 52 publications

References 20 publications

Material and Morphological Heat Transfer Properties of Fuel Cell Porous Transport Layers

Material and Morphological Heat Transfer Properties of Fuel Cell Porous Transport Layers

3D analysis, modeling and simulation of transport processes in compressed fibrous microstructures, using the Lattice Boltzmann method

Advanced Water Management in PEFCs: Diffusion Layers with Patterned Wettability

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