Analysis of Oxygen Transport Resistance Components and Water Transport Phenomena with Hydrophilic and Hydrophobic MPL in PEFC

Nozaki, Ryo; Tabe, Yutaka; Chikahisa, Takemi; Tanuma, Toshihiro

doi:10.1149/08008.0335ecst

Cited by 5 publications

(5 citation statements)

References 9 publications

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“…The pressure independent resistance can be assumed to correspond approximately to the oxygen transport resistance in the CL, the Knudsen diffusion resistance in the pores of the CL, and the transport resistance from the gas in the pores to the Pt surface through the ionomer, and this allows the oxygen transport resistance in the CL to be evaluated quantitatively. The results suggest that the oxygen transport resistance in the CL with the hydrophilic CF-MPL is maintained lower than that with the hydrophobic CB-MPL at high current densities, 22 supporting the experimentally suggested water transport illustrated in Fig. 10 that the hydrophilic CF-MPL promotes the draining of water from the CL to the MPL.…”

Section: Ice Distributions In the Four Types Of The Mplssupporting

confidence: 80%

“…10 that the hydrophilic CF-MPL promotes the draining of water from the CL to the MPL. Although the above results are limited to a specific condition and further detailed analyses such as the limiting current 22 and oxygen gain 23 analyses are necessary for a more precise evaluation of the oxygen transport resistance in the CL, it may be concluded that the hydrophilic CF-MPL enhances the transport of liquid water in the CL due to the hydrophilic fibers. The MPL structure with the large pores and sufficient thickness provides a superior environment to evaporate the water in the MPL, and this results in the better anti-flooding performance at high current densities, as shown in the comparison of the cell performances (Figs.…”

Section: F491mentioning

confidence: 96%

“…Recently, the authors have developed the limiting current analysis 20,21 to apply to flooded conditions. 22 In that analysis the total oxygen transport resistance in the cell, which is affected by the liquid water accumulated in the cell, is divided into two resistances: the resistance dependent on the total pressure of the cathode gas and that independent of the total pressure. The pressure independent resistance can be assumed to correspond approximately to the oxygen transport resistance in the CL, the Knudsen diffusion resistance in the pores of the CL, and the transport resistance from the gas in the pores to the Pt surface through the ionomer, and this allows the oxygen transport resistance in the CL to be evaluated quantitatively.…”

Section: Ice Distributions In the Four Types Of The Mplsmentioning

confidence: 99%

See 2 more Smart Citations

Analysis of Water Transport inside Hydrophilic Carbon Fiber Micro-Porous Layers with High-Performance Operation in PEFC

Aoyama

Tabe

Nozaki

et al. 2018

J. Electrochem. Soc.

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Polymer electrolyte membrane fuel cells using a hydrophilic micro-porous layer (MPL) consisting of carbon fiber (CF) and ionomer show better performance than those using conventional hydrophobic MPL with carbon black (CB) under a wide range of humidity conditions. This study investigates the effects of the wettability and structure of the MPL on cell performance and discusses the mechanism for improving cell performance by the hydrophilic CF-MPL at high humidity conditions. The water distribution inside the MPL is evaluated by a freezing method and cryo-SEM observations, and a comparison of the distribution and the cell performance of hydrophilic and hydrophobic MPL cells with various structures is made. The results show that the performance improvement is caused by preventing increases in concentration overvoltage at high current densities; where the fiber structure and thicker layers are important with hydrophilic MPL. In hydrophilic CF-MPL with better performance, liquid water accumulates in pores at the catalyst layer (CL) side, while there is no liquid water at the gas diffusion layer side. These results indicate that the hydrophilic CF-MPL enhances the liquid water transport from the CL due to the hydrophilic properties, and promotes water evaporation due to the large pores in the thick fiber structure.

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Section: Ice Distributions In the Four Types Of The Mplssupporting

confidence: 80%

Section: F491mentioning

confidence: 96%

Section: Ice Distributions In the Four Types Of The Mplsmentioning

confidence: 99%

See 1 more Smart Citation

Analysis of Water Transport inside Hydrophilic Carbon Fiber Micro-Porous Layers with High-Performance Operation in PEFC

Aoyama

Tabe

Nozaki

et al. 2018

J. Electrochem. Soc.

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“…However, PTFE was neglected and not fully reconstructed in their work. Hannach et al [ 22 ] obtained a realistic 3D MPL microstructure, Lee et al [ 17 ], Deng et al [ 28 ], Bock et al [ 8 ], Aoyama et al [ 29 ], and Nozaki et al [ 30 ] studied the transport of gas-water-heat-electricity in MPL. However, only a few of the published works considered the effect of mechanical compression on the MPL transport properties.…”

Section: Introductionmentioning

confidence: 99%

Pore-Scale Modeling of Microporous Layer for Proton Exchange Membrane Fuel Cell: Effective Transport Properties

et al. 2023

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A microporous layer (MPL) is a transition layer with a porous material structure, located between the gas diffusion layer (GDL) and catalyst layer (CL) in a proton exchange membrane fuel cell (PEMFC). It not only significantly improves electron transfer and heat conduction in membrane electrode assembly, but also effectively manages liquid water transport to enhance the fuel cell performance. The MPL is usually coated on one side of the GDL. The fragile nature of MPL makes it challenging to characterize the effective transport properties using experimental methods. In this study, a stochastic numerical method is implemented to reconstruct the three-dimensional microstructure of an MPL consisting of carbon particles and PTFE. The reliability of the MPL reconstructed model is validated using experimental data. The relationship between the effective transport properties and the compression strain is obtained using the Pore Scale Model (PSM), while the relationship between the liquid water saturation and capillary pressure is solved by Lattice Boltzmann Method (LBM). The effective transport properties in the MPL are then imported into the two-phase flow fuel cell model. It is found that the effective transport parameters in MPL obtained by PSM and LBM can improve the accuracy of the model calculation. This study provides an effective method to reconstruct the microstructure of MPL that can generate precise MPL transport parameters for utilization in various PEMFC performance prediction models.

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“…The combined effects of relative humidity and current density on liquid water accumulation and oxygen transport resistance were investigated (2). Our previous study extended the limiting current method to flooding conditions, and analyzed quantitatively the effects of condensed water on the resistance components of oxygen transport inside and outside the catalyst layer (CL) (7). It was also reported that a hydrophilic MPL with carbon fiber (CF) and ionomer has the effect of wicking liquid water from the CL under flooding conditions, and its performance is improved compared to a hydrophobic MPL with carbon black (CB) (8).…”

Section: Introductionmentioning

confidence: 99%

Control of the Balance between Vapor and Heat Transfer for the Reduction of Oxygen Transport Resistance in High Current Density PEFC Operation

2019

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This study confirmed the unusual increase in oxygen transport resistance at higher current densities during high temperature operation: the increase becomes more pronounced with the lower relative humidity of the supplied gas. To investigate the causes, we estimated the relative humidity in the catalyst layer (CL) using a vapor diffusion and heat conduction model, which shows drier state in the CL with higher current densities under the high temperature conditions. Water distribution in the cell after the unusual increase was also observed using freezing method, and it was confirmed that there is no liquid water around the CL and MPL. These suggest that the increase in oxygen transport resistance is caused by deterioration of oxygen permeability through the ionomer due to decrease in the water content. In addition, we tried to reduce oxygen transport resistance at higher current densities by controlling the balance between the vapor diffusion and heat conduction.

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Analysis of Oxygen Transport Resistance Components and Water Transport Phenomena with Hydrophilic and Hydrophobic MPL in PEFC

Cited by 5 publications

References 9 publications

Analysis of Water Transport inside Hydrophilic Carbon Fiber Micro-Porous Layers with High-Performance Operation in PEFC

Analysis of Water Transport inside Hydrophilic Carbon Fiber Micro-Porous Layers with High-Performance Operation in PEFC

Pore-Scale Modeling of Microporous Layer for Proton Exchange Membrane Fuel Cell: Effective Transport Properties

Control of the Balance between Vapor and Heat Transfer for the Reduction of Oxygen Transport Resistance in High Current Density PEFC Operation

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