In situ observation of the water distribution across a PEFC using high resolution neutron radiography

Boillat, Pierre; Kramer, Denis; Seyfang, Bernhard C.; Frei, G.; Lehmann, Eberhard; Scherer, Günther G.; Wokaun, Alexander; Ichikawa, Yasushi; Tasaki, Yutaka; Shinohara, Kazuhiko

doi:10.1016/j.elecom.2008.01.018

Cited by 226 publications

(134 citation statements)

References 16 publications

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“…Neutron radiography is highly sensitive to liquid water in PEM fuel cell studies due to the high attenuation caused by hydrogen-containing atoms. This technique has therefore been very useful in liquid water transport research [30][31][32][33][34][35][36][37]. Neutron-based PEM fuel cell studies are generally limited to spatial resolutions of 25 μm at temporal resolutions of 5.4 s [25].…”

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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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%

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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“…To elucidate the mechanism of water transport phenomena experimentally, some work has attempted to visualize the liquid water in a PEFC [10][11][12][13][14]. For the cross-sectional visualization of the liquid water inside porous structures like GDL, published studies have commonly used neutron radiography [10,11] and X-ray radiography [12,13]. Vapor condensation and liquid water breakthrough in the porous structures at the surface of the CL were observed by environmental scanning electron microscopy [14].…”

Section: Introductionmentioning

confidence: 99%

“…The morphology of the CL and MPL surfaces has been characterized in detail [7], and the effects of the interfacial morphology on the ohmic, thermal, and mass-transport losses were investigated numerically [8,9]. To elucidate the mechanism of water transport phenomena experimentally, some work has attempted to visualize the liquid water in a PEFC [10][11][12][13][14]. For the cross-sectional visualization of the liquid water inside porous structures like GDL, published studies have commonly used neutron radiography [10,11] and X-ray radiography [12,13].…”

Section: Introductionmentioning

confidence: 99%

Impact of micro-porous layer on liquid water distribution at the catalyst layer interface and cell performance in a polymer electrolyte membrane fuel cell

Tabe

Aoyama

Kadowaki

et al. 2015

Journal of Power Sources

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In polymer electrolyte membrane fuel cells, a gas diffusion layer (GDL) with a micro-porous layer (MPL) gives better anti-flooding performance than GDLs without an MPL. To investigate the function and mechanism of the MPL to suppress water flooding, the liquid water distribution at the cathode catalyst layer (CL) surface are observed by a freezing method; in the method liquid water is immobilized in ice form by rapid freezing, followed by disassembling the cell for observations. The ice covered area is quantified by image processing and cells with and without an MPL are compared. The results show that the MPL suppresses water accumulation at the interface due to smaller pore size and finer contact with the CL, and this results in less water flooding. Investigation of ice formed after −10 °C cold start shutdowns and the temporary performance deterioration at ordinary temperatures also indicates a significant influence of the liquid water accumulating at the interface. The importance of the fine contact between CL and MPL, the relative absence of gaps, is demonstrated by a gas diffusion electrode (GDE) which is directly coated with catalyst ink on the surface of the MPL achieving finer contact of the layers. Highlights• Liquid water distribution at the cathode catalyst layer (CL) surface is observed.• Performance deteriorates due to the liquid water accumulated on the CL surface.• The MPL reduces liquid water accumulation between the CL and the MPL.• Cold startup induces much water accumulation and temporary performance deterioration.• A gas diffusion electrode with fine CL to MPL contact mitigates the flooding.

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“…1 Water transport in fuel cell materials is commonly described by two-phase flow models, which take into account the complex transport interactions between liquid and gaseous phases, 1,3-5 and numerous theoretical and experimental reports focusing on two-phase flow have been crucial for understanding the basics of water transport. 3,4,[6][7][8][9][10][11][12][13][14][15][16] In recent years, neutron radiography, 10-13 magnetic resonance imaging, 14 and ͑to a limited extent͒ x-ray imaging [15][16][17] have been applied to visualize liquid water flow in fuel cells. However, until recently, it was not possible to quantify local water transport ͑exchange͒ rates inside fuel cell materials, i.e., the rates at which the accumulated water is exchanged by newly produced water from the cathode, especially under stationary conditions where the local water amount remains almost constant.…”

mentioning

confidence: 99%

Characterization of water exchange and two-phase flow in porous gas diffusion materials by hydrogen-deuterium contrast neutron radiography

Manke

Hartnig

Kardjilov

et al. 2008

Applied Physics Letters

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Liquid water exchange in two-phase flows within hydrophobic porous gas diffusion materials of polymer electrolyte membrane fuel cells was investigated spatially resolved with H–D contrast neutron radiography. A commonly used one-phase model is sufficient to describe water exchange characteristics at low water production rates. At higher rates, however, a significantly higher exchange velocity is found than predicted by a simple model. A new model for the water transport is derived based on an eruptive mechanism guided by Haines jumps, which is supported by recent experimental findings and leads to a very good agreement with the experiments.

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In situ observation of the water distribution across a PEFC using high resolution neutron radiography

Cited by 226 publications

References 16 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 micro-porous layer on liquid water distribution at the catalyst layer interface and cell performance in a polymer electrolyte membrane fuel cell

Characterization of water exchange and two-phase flow in porous gas diffusion materials by hydrogen-deuterium contrast neutron radiography

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