Synchrotron radiography and tomography of water transport in perforated gas diffusion media

Haußmann, Jan; Markötter, Henning; Alink, Robert; Bauder, Alexander; Dittmann, Katja; Manke, Ingo; Scholta, Joachim

doi:10.1016/j.jpowsour.2013.02.014

Cited by 93 publications

(62 citation statements)

References 43 publications

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“…Synchrotron X-ray radiography offers high spatial and temporal resolutions (less than 10 μm and less than 10 s, respectively) [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57]. Though X-ray photons are not as sensitive as a neutron beam to the presence of liquid water, Chevalier et al [29] demonstrated that synchrotron X-ray radiography can achieve similar accuracy to neutron radiography with a high level of precision.…”

Section: Visualizations Of Liquid Water Saturationmentioning

confidence: 99%

“…Recent works have improved the accuracy and reliability of this technique for PEM fuel cell visualizations by establishing methodologies for correcting beam position movement artifacts [58], calibrating the attenuation coefficient of liquid water and correcting sample movement artifacts [44], and considering photon scattering and harmonics [59]. In addition, the fast temporal resolutions possible with synchrotron X-ray radiography allow for dynamic visualizations of transient liquid water behaviour [60,61] and enable high-resolution in-situ tomography to resolve liquid water saturation in 3-D [48,52,62].…”

Section: Visualizations Of Liquid Water Saturationmentioning

confidence: 99%

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Liquid water saturation and oxygen transport resistance in polymer electrolyte membrane fuel cell gas diffusion layers

Muirhead

Banerjee

George

et al. 2018

Electrochimica Acta

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In this thesis, the relative humidity (RH) of the cathode reactant gas was investigated as a factor which influences gas diffusion layer (GDL) liquid water accumulation and mass transport-related efficiency losses over a range of operating current densities in a polymer electrolyte membrane (PEM) fuel cell. Limiting current measurements were used to characterize fuel cell oxygen transport resistance while simultaneous measurements of liquid water accumulation were conducted using synchrotron X-ray radiography. GDL porosity distributions were characterized with micro-computed tomography (μCT). The work presented here can be used by researchers to develop improved numerical models to predict GDL liquid water accumulation and to inform the design of next-generation GDL materials to mitigate mass transport-related efficiency losses. This work also contributes an extensive set of concurrent performance and liquid water visualization data to the PEM fuel cell field that can be used for validating multiphase transport models.iii

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Section: Visualizations Of Liquid Water Saturationmentioning

confidence: 99%

Section: Visualizations Of Liquid Water Saturationmentioning

confidence: 99%

Liquid water saturation and oxygen transport resistance in polymer electrolyte membrane fuel cell gas diffusion layers

Muirhead

Banerjee

George

et al. 2018

Electrochimica Acta

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“…6,10 These are either random defects in the microporous layer 11,12 or purposely designed defects. [13][14][15][16][17][18] There exist several X-ray imaging studies, which describe the liquid water transport through perforations and cracks. 14,[19][20][21] Fuel cell tests of these types of materials have shown that specifically engineered large pores in the MPL/GDL-S can enhance the overall fuel cell performance, increase the limiting current density and accordingly reduce the oxygen transport resistance.…”

mentioning

confidence: 99%

Impact of Microporous Layer Pore Properties on Liquid Water Transport in PEM Fuel Cells: Carbon Black Type and Perforation

Simon

Kartouzian

Müller

et al. 2017

J. Electrochem. Soc.

110

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The oxygen and water transport through various microporous layers (MPLs) is investigated by fuel cell tests in a 5 cm 2 active area cell under differential-flow conditions, analyzing polarization curves, the associated high-frequency resistance, and the oxygen transport resistance extracted from limiting current density measurements. In this study, MPLs with two different carbon blacks are prepared and compared to a commercial material, all coated on the same GDL-substrate (Freudenberg); furthermore, perforated MPLs with large pores produced by a thermally decomposable polymeric pore former with a particle diameter of ≈30 μm are examined. The materials are characterized by mercury porosimetry, nitrogen adsorption and scanning electron microscopy. While at dry conditions (T cell = 80 • C, RH = 70%, p abs = 170 kPa) the performance of all materials is similar, at conditions of high water saturation (T cell = 50 • C, RH = 120%, p abs = 300 kPa), MPLs with larger pores or perforations exhibit a performance improvement due to a ≈30% reduction in oxygen transport resistance. The results indicate that liquid water is transported exclusively through these large pores, while the oxygen transport occurs in the small pores defined by the carbon black structure.

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“…Haußmann et al 30,31 visualized liquid water accumulation in the cracks and large holes of the MPL, and they suggested that these macro features were prone to liquid water accumulation. Lee et al 34 investigated the impact of MPL thickness on the water distribution in the GDL.…”

mentioning

confidence: 99%

Multiwall Carbon Nanotube-Based Microporous Layers for Polymer Electrolyte Membrane Fuel Cells

Lee

Banerjee

George

et al. 2017

J. Electrochem. Soc.

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The presence of multiwall carbon nanotubes (MWCNTs) corresponded to a dispersion of carbon black particles in the microporous layer (MPL) of the polymer electrolyte membrane (PEM) fuel cell. The gas diffusion layer (GDL) with a MWCNT-based MPL exhibited larger pores and a higher porosity compared to a conventional GDL, and less MPL intrusion into the GDL substrate was observed with the MWCNTs-based MPL. The GDLs were evaluated in operando in a fuel cell that was customized for concurrent liquid water visualization (synchrotron X-ray radiography) and electrochemical characterization. The MWCNT-based fuel cell exhibited higher power densities and lower mass transport resistances compared to the fuel cell with the conventional GDL; however, a higher liquid water saturation was observed for the MWCNT-based GDL. Although the liquid water saturation in the MWCNTbased GDL was higher, its higher effective porosity led to superior performance compared to the conventional fuel cell. The use of the MWCNTs-based MPL resulted in improved oxygen transport in the fuel cell, particularly at high current densities. The achievement of effective water management in the polymer electrolyte membrane (PEM) fuel cell remains a challenge. Excess liquid water accumulation in the gas diffusion layer (GDL) hinders the transport of oxygen in the fuel cell. Reduced oxygen diffusion in the liquid water saturated GDL leads to efficiency losses and unstable performance.1,2 However, the commonly used bi-layered GDL (containing a carbon fiber substrate and a microporous layer (MPL)) has been shown to enhance liquid water management and the overall performance of the fuel cell. [3][4][5][6][7][8] In recent years, significant effort has been devoted to developing novel carbon fiber substrates and MPLs.9-18 Thomas et al. 9 developed a novel method for preparing hydrophobic GDLs via the electrochemical reduction of diazonium salts. GDLs were prepared with homogenous hydrophobicity distributions in the absence of pore structure modifications. Nguyen et al. 10 introduced the direct fluorination of the GDL for providing homogenous hydrophobicity. Less liquid water content was observed in these novel GDLs compared to the conventional GDL (SGL 24 BC) when visualized with soft X-rays. In the works of Forner-Cuenca et al.,11,12 a patterning of wettability was applied to a Toray GDL through radiation grafting. Hydrophilic regions facilitated preferential pathways for liquid water transport, while hydrophobic regions facilitated gas transport. Chevalier et al.13 created a novel GDL via electrospinning and radiation grafting. Ko et al.14 proposed a novel GDL through the dry deposition of hydrophobic silicone nanolayer on carbon fibers. The longterm operational stability and dynamic response of the GDL were improved.On the other hand, a number of works have focused on MPL additives for improving water management in fuel cells.19-29 While conventional MPLs consist of carbon black particles and a hydrophobic agent, such as polytetrafluoroethylene (PTFE), recent ...

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Synchrotron radiography and tomography of water transport in perforated gas diffusion media

Cited by 93 publications

References 43 publications

Liquid water saturation and oxygen transport resistance in polymer electrolyte membrane fuel cell gas diffusion layers

Liquid water saturation and oxygen transport resistance in polymer electrolyte membrane fuel cell gas diffusion layers

Impact of Microporous Layer Pore Properties on Liquid Water Transport in PEM Fuel Cells: Carbon Black Type and Perforation

Multiwall Carbon Nanotube-Based Microporous Layers for Polymer Electrolyte Membrane Fuel Cells

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