Quantification of Temperature Driven Flow in a Polymer Electrolyte Fuel Cell Using High-Resolution Neutron Radiography

Hatzell, Marta C.; Turhan, Ahmet; Kim, Yu Seung; Hussey, Daniel S.; Jacobson, David L.; Mench, Matthew M.

doi:10.1149/1.3577597

Cited by 55 publications

(52 citation statements)

References 63 publications

(143 reference statements)

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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%

“…Neutron-based PEM fuel cell studies are generally limited to spatial resolutions of 25 μm at temporal resolutions of 5.4 s [25]. However, researchers have achieved spatial resolutions as small as 15.4 μm with a temporal resolution of 54 s [30] and 2.5 μm with a temporal resolution of 5 minutes using specialized detection systems [31].…”

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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“…PCI flow has been studied in the literature either by experimental in situ measurements 17,18 or using 1D non-isothermal, two-phase models to simulate water evaporation/condensation quantitatively. 19 The temperature-gradientinduced water flux measurements conducted by Mench et al 17,18 through a non-operating and operating fuel cell show the importance of the PCI flow at various temperatures. Weber et al 19 coupled thermal and water management together with a non-isothermal 1D model to investigate the transport of water due to the temperature gradient.…”

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confidence: 99%

A Mixed Wettability Pore Size Distribution Based Mathematical Model for Analyzing Two-Phase Flow in Porous Electrodes

Zhou

Pütz

Secanell

2017

J. Electrochem. Soc.

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A multi-dimensional, non-isothermal, two-phase membrane electrode assembly (MEA) numerical model is developed where the micro-structure of the porous layers is characterized by a mixed wettability pore size distribution (PSD). The PSD model is used to predict local water saturation based on gas and liquid pressures, and can be used to study the effect of varying pore size and wettability. The MEA model accounts for gas transport via molecular and Knudsen diffusion, liquid water transport, sorbed water transport by back-diffusion, electro-and thermo-osmosis, and heat generation and transport. Multi-step kinetic models are used to predict anode and cathode electrochemical reactions. Local transport losses are accounted for using a local transport resistance. The PSD model is used to predict capillary pressure vs. saturation and saturation vs. relative liquid permeability curves based on PSDs from several GDLs obtained using mercury intrusion porosimetry. The PSD-based MEA model electrochemical performance predictions are also compared to experimental data from the literature. Results show that the numerical model is able to capture the performance changes associated with varying temperate and the introduction of a micro-porous layer. Improving the performance of polymer electrolyte fuel cells (PEFCs) at high current density is critical for reducing stack size, cost and weight in automobile applications. Water accumulation in the electrode however, limits fuel cell performance at high current densities. [1][2][3] In order to mitigate the excessive water buildup in the cell, which hinders mass transport, gas diffusion layer (GDL) and catalyst layer (CL) microstructures and wettabilities must be advanced to achieve sufficient water retention in the electrolyte, reject excess water in vapor form and alleviate complete flooding of the electrode. For example, by modifying the weight percentage (wt%) of the hydrophobic content in the GDL, Wang et al. 4 reported a 10%-20% increase in performance. To understand fuel cell behavior in the two-phase region and optimize the design of GDL and CL, a two-phase model which includes microstructural information of the porous layers is needed.Two approaches have commonly been used to study liquid water transport in fuel cells. The first approach involves the solution of a saturation equation obtained by replacing liquid pressure by saturation in Darcy's law. [5][6][7] In this approach the Levertt J-function is commonly used to relate saturation with capillary pressure. The Leverett J-function is however, an empirically measured curve for a given material and it is obtained from porous media structure analysis. Thus, it is difficult to optimize the structure of the porous layers using Leverett J-functions. The second approach, known as the multi-phase approach, involves solving mass and momentum equations for gas and liquid phases independently and then relating the capillary pressure to saturation using a closure equation based on micro-structural information such as a pore size dist...

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“…There are a variety of methods to visualize how the produced water is removed from the reaction area, including optical visualization with transparent cells, 11 scanning electron microscopy (SEM), 12 X-ray radiography, [13][14][15][16] and neutron radiography. 17 Sasabe et al visualized water accumulation and discharge in an operating cell by a soft X-ray radiographic technique, and suggested that the MPL prevents the accumulation of water in the substrate layer. 13 Deevanhxay et al observed water accumulation and transport in the cathode side MPL and GDL, and suggested that the water generated from the cell reactions was transported to the GDL mainly through cracks in the MPL.…”

mentioning

confidence: 99%

Water Transport and PEFC Performance with Different Interface Structure between Micro-Porous Layer and Catalyst Layer

Aoyama

Suzuki

Tabe

et al. 2016

J. Electrochem. Soc.

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For interfaces between micro-porous layers (MPL) and catalyst layers (CL) made by the gas diffusion electrode (GDE) method, a seamless interface without gaps, shows better performance than that of cells with an interface made by the decal transfer method. With the decal transfer method, the MPL is simply hot-pressed to the CL-membrane assembly. This study investigates the effect of interface structure on cell performance and water transport in the MPL. Water distribution in cross sections of multiple layers were observed by a freezing method, where the cell is cooled below freezing temperature in short time and the water was observed in ice form by Cryo-SEM. The results show that a membrane electrode assembly (MEA) using the GDE method improves cell performance at high current densities. Direct observations by the freezing method and cryo-SEM show that there is no water accumulation at the MPL/CL interface made by the GDE method, while water accumulates at the interface made by the decal method. Other observations show that the water amount inside the MPL increases similarly in the two types of MEA when lowering the temperature, and the difference between the two types of MEA was only the water amount in the interface. Polymer electrolyte fuel cells (PEFCs) are promising power sources for next generation vehicles, motorcycles, and residential cogeneration systems (the so-called combined heat and power; CHP). However, there is considerable potential for improvements in the performance for the PEFC to become practical in many other applications. Water flooding, the blockage of the gas supply to the reaction area by accumulation of water, is one of the major issues with the PEFC, as cell performance deteriorates significantly under high current density conditions. Micro-porous layers (MPLs), typically consisting of carbon black and a hydrophobic polymer, have been demonstrated to be an important component in improving the water management of the PEFC.The effect of a hydrophobic MPL on the water transport mechanism in the cell has been investigated by computational and experimental studies, and these studies have suggested that the MPL removes produced water from the reaction area.1-5 Weber et al. and Pasaogullari et al. reported that the MPL reduces the amount of water passing through the cathode side of the gas diffusion layer (GDL) by increasing the water flow from cathode to anode.1,2 Gostick et al. and Lu et al. suggested that cracks in the MPL are the pathways of the water discharge, and that this results in reductions in the water saturation in the GDL.3,4 Owejan et al. investigated water transport in the MPL by measuring the performance of cells with various types of MPL, and proposed that the MPL prevents the water in the GDL from contacting with and forming a water film on the catalyst layer (CL) surface.5 They also investigated the water vapor transport capacity through the MPL driven by the saturation pressure gradient in the cathode diffusion layer due to the temperature gradient, and demonstrated that ...

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Quantification of Temperature Driven Flow in a Polymer Electrolyte Fuel Cell Using High-Resolution Neutron Radiography

Cited by 55 publications

References 63 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

A Mixed Wettability Pore Size Distribution Based Mathematical Model for Analyzing Two-Phase Flow in Porous Electrodes

Water Transport and PEFC Performance with Different Interface Structure between Micro-Porous Layer and Catalyst Layer

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