Liquid Water Transport in Gas Diffusion Layer of Polymer Electrolyte Fuel Cells

Pasaogullari, Ugur; Wang, C. Y.

doi:10.1149/1.1646148

Cited by 640 publications

(449 citation statements)

References 17 publications

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“…9 It must also permit transport of gas reactants and liquid product between the gas flow channels and the catalyst/PEM interface. 4,10,11 The porous electrode, or gas diffusion layer (GDL), of the fuel cell is typically made from carbon fibers, either as a random sheet of fibers in the form of carbon paper or as a woven array of fiber bundles forming carbon cloth. 12,13 These sheets of carbon fibers may be treated with adsorbed polymer layers to improve their function in fuel cells.…”

Section: ■ Introductionmentioning

confidence: 99%

Drop Detachment and Motion on Fuel Cell Electrode Materials

Gauthier

Hellstern

Kevrekidis

et al. 2012

ACS Appl. Mater. Interfaces

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Liquid water is pushed through flow channels of fuel cells, where one surface is a porous carbon electrode made up of carbon fibers. Water drops grow on the fibrous carbon surface in the gas flow channel. The drops adhere to the superficial fiber surfaces but exhibit little penetration into the voids between the fibers. The fibrous surfaces are hydrophobic, but there is a substantial threshold force necessary to initiate water drop motion. Once the water drops begin to move, however, the adhesive force decreases and drops move with minimal friction, similar to motion on superhydrophobic materials. We report here studies of water wetting and water drop motion on typical porous carbon materials (carbon paper and carbon cloth) employed in fuel cells. The static coefficient of friction on these textured surfaces is comparable to that for smooth Teflon. But the dynamic coefficient of friction is several orders of magnitude smaller on the textured surfaces than on smooth Teflon. Carbon cloth displays a much smaller static contact angle hysteresis than carbon paper due to its two-scale roughness. The dynamic contact angle hysteresis for carbon paper is greatly reduced compared to the static contact angle hysteresis. Enhanced dynamic hydrophobicity is suggested to result from the extent to which a dynamic contact line can track topological heterogeneities of the liquid/solid interface. KEYWORDS: contact angle, hydrophobic, carbon, wetting, carbon fibers, contact angle hysteresis, Teflon ■ INTRODUCTIONWater transport is an essential element of polymer electrolyte membrane (PEM) fuel cell operation. 1−5 Liquid water that is formed at a catalyst/membrane interface is pushed through porous electrodes into gas flow channels. The water drops emerge from the largest pores in the electrode, and grow in the channel. Initially, the drops are held in place by adhesion to the water column in the electrode pore, but as the drops grow surface contact with the porous electrode and surface contact with the walls of the flow channel are the dominate adhesive forces. The drop must be detached and pushed through the gas flow channel in contact with the electrode surface to be removed from the fuel cell. Efficient fuel cell operation requires removal of liquid water drops from the fuel cell with minimal work. The surface properties of the porous electrode play a key role in the energy required to remove water drops from the gas flow channels of the fuel cell. We have been devising experiments to isolate the flow resistances for water transport through the porous electrode and gas flow channel. 6−8 The porous electrode is required to carry the electron current from the electrocatalyst to the external circuit. 9 It must also permit transport of gas reactants and liquid product between the gas flow channels and the catalyst/PEM interface. 4,10,11 The porous electrode, or gas diffusion layer (GDL), of the fuel cell is typically made from carbon fibers, either as a random sheet of fibers in the form of carbon paper or as a woven arr...

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Section: ■ Introductionmentioning

confidence: 99%

Drop Detachment and Motion on Fuel Cell Electrode Materials

Gauthier

Hellstern

Kevrekidis

et al. 2012

ACS Appl. Mater. Interfaces

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“…Several studies have been conducted on two-phase flows in PEM fuel cells. Theoretical one-dimensional models for liquid water transport in gas diffusion layers (GDLs), where liquid water is controlled by capillary forces depending on the structure and wettability of GDL, have been reported [1,2], and three-dimensional simulations using two-phase models have been developed [3,4]. For liquid water transport in gas flow channels, experimental investigations have been conducted using transparent fuel cells and it was demonstrated that the surface tension of water and the wettability of the GDL and gas flow channel play a dominant role in the liquid water transport [5,6].…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of liquid water and gas flow in a channel and a simplified gas diffusion layer model of polymer electrolyte membrane fuel cells using the lattice Boltzmann method

Tabe

Lee

Chikahisa

et al. 2009

Journal of Power Sources

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Numerical simulations using the lattice Boltzmann method (LBM) are developed to elucidate the dynamic behavior of condensed water and gas flow in a polymer electrolyte membrane (PEM) fuel cell. Here, the calculation process of the LBM simulation is improved to extend the simulation to a porous medium like a gas diffusion layer (GDL), and a stable and reliable simulation of two-phase flow with large density differences in the porous medium is established. It is shown that dynamic capillary fingering can be simulated at low migration speeds of liquid water in a modified GDL, and the LBM simulation reported here, which considers the actual physical properties of the system, has significant advantages in evaluating phenomena affected by the interaction between liquid water and air flows. Two-phase flows with the interaction of the phases in the two-dimensional simulations are demonstrated. The simulation of water behavior in a gas flow channel with air flow and a simplified GDL shows that the wettability of the channel has a strong effect on the two-phase flow. The simulation of the porous separator also indicates the possibility of controlling two-phase distribution for better oxygen supply to the catalyst layer by gradient wettability design of the porous separator.Keywords: PEM fuel cell, Lattice Boltzmann method, Two-phase flow, Large density difference, Gas diffusion layer, Wettability

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“…On the other hand, deficiency of water decreases the proton conductivity of the membrane and thus humidification of reactants is typically needed. Water management has a considerable effect on fuel cell performance and the process is highly sensitive to operational and material parameters [9][10][11][12][13]. Water transport inside the fuel cell has a close link to temperature distribution since water and oxygen diffusivity, saturation parameters, and reaction kinetics are all temperature dependent, see, e.g.…”

Section: Introductionmentioning

confidence: 99%

Thermal Conductivity and Contact Resistance of Compressed Gas Diffusion Layer of PEM Fuel Cell

Nitta¹,

Himanen

Mikkola³

2008

Fuel Cells

106

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Faculty DepartmentAuthor ( This paper discusses the effect of compression pressure on the mechanical and thermal properties of gas diffusion layers (GDL).The stress-strain curve of the GDL revealed one nonlinear and two piecewise linear regions within the compression pressure range of 0 to 5.5 MPa. The thermal conductivity of the compressed GDL was found to be independent of the compression pressure and was determined to be 1.18 ± 0.11 W m-1 K-1. The thermal contact resistance between the GDL and graphite was evaluated by augmenting experiments with computer modeling. The thermal contact resistance decreased nonlinearly with increasing compression pressure. According to results here, the thermal bulk resistance of the GDL is comparable to the thermal contact resistance between the GDL and graphite. A simple one dimensional model predicted a temperature drop of 1.7-4.4 ˚C across the GDL and catalyst layer depending on compression pressures.

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Liquid Water Transport in Gas Diffusion Layer of Polymer Electrolyte Fuel Cells

Cited by 640 publications

References 17 publications

Drop Detachment and Motion on Fuel Cell Electrode Materials

Drop Detachment and Motion on Fuel Cell Electrode Materials

Numerical simulation of liquid water and gas flow in a channel and a simplified gas diffusion layer model of polymer electrolyte membrane fuel cells using the lattice Boltzmann method

Thermal Conductivity and Contact Resistance of Compressed Gas Diffusion Layer of PEM Fuel Cell

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