Ex-situ visualization of the wet domain in the microporous layer in a polymer electrolyte fuel cell by X-ray computed tomography under water vapor supply

Kato, Satoru; Yamaguchi, S.; Yoshimune, Wataru; Matsuoka, Yoriko; Kato, Akihiko; Suzuki, Takahisa; Suzuki, Tomomichi

doi:10.1016/j.elecom.2019.106644

Cited by 24 publications

(23 citation statements)

References 34 publications

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“…Jo et al [ 16 ] conducted a study in which they cooled a superhydrophobic PTFE surface in an ESEM (environment scanning electron microscope) with constant vapor pressure and observed water condensation from inside the hydrophobic interstices. Kato et al [ 24 ] carried out a study on water condensation in the hydrophobic microporous layer (MPL) of polymer electrolyte fuel cells and showed that water condensation and accumulation could happen in a MPL. Guillen-Burrieza et al [ 12 ] also reported similar phenomena in a membrane distillation study, in which temperature reduction during an experiment led to rapid conductivity increase, which was a convenient indication of membrane wetting in a membrane distillation system.…”

Section: Resultsmentioning

confidence: 99%

Discussion on Water Condensation in Membrane Pores during CO2 Absorption at High Temperature

Chan

Kang

et al. 2020

Membranes

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Water condensation is a possible cause of membrane wetting in the operation of membrane contactors, especially under high-temperature conditions. In this study, water condensation in pores of polytetrafluoroethylene (PTFE) hollow fiber membranes was investigated during high-pressure CO2 absorption around 70 °C. It was found that the liquid accumulation rate in the treated gas knock-out drum was constant during continuous operation for 24 h when all experimental conditions were fixed, indicating a stable degree of membrane wetting. However, as the operating parameters were changed, the equilibrium vapor pressure of water within membrane pores could change, which may result in a condensation-conducive environment. Water condensation in membrane pores was detected and proven indirectly through the increase in liquid accumulation rate in the treated gas knock-out drum. The Hagen–Poiseuille equation was used to correlate the liquid accumulation rate with the degree of membrane wetting. The degree of membrane wetting increased significantly from 1.8 × 10−15 m3 to 3.9 × 10−15 m3 when the feed gas flow rate was reduced from 1.45 kg/h to 0.40 kg/h in this study due to water condensation in membrane pores. The results of this study provide insights into potential operational limitations of membrane contactor for CO2 absorption under high-temperature conditions.

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Section: Resultsmentioning

confidence: 99%

Discussion on Water Condensation in Membrane Pores during CO2 Absorption at High Temperature

Chan

Kang

et al. 2020

Membranes

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“…e XRCT images were reconstructed using so ware developed by Uesugi (2020). Water clusters were identi ed by subtracting the dry GDL image from the water-injected GDL images using a method similar to that described in a previous paper (Kato et al, 2020). e so ware package ExFact VR ® (Nihon Visual Science, Inc.) was used to trim the reconstructed images and eliminate noise.…”

Section: Analysis Of Xrct Datamentioning

confidence: 99%

“…A correlation between porosity and water saturation in the substrate was found by a water-injecting approach (Zenyuk et al, 2015;Lamibrac et al, 2016). Although the water intrusion behavior has been studied using the lattice Boltzmann method (Mukherjee et al, 2009;Kim et al, 2015;Sakaida et al, 2019), a pore network model (Inoue et al, 2008;Agaesse et al, 2016), and visualization experiments (Afra et al, 2019;Kato et al, 2020), structures of water-cluster network features such as dead ends and permeation paths, which contribute to the drainage of water from the GDL, are still not clearly understood.…”

Section: Introductionmentioning

confidence: 99%

<i>Ex situ</i> Visualization and Network Analysis of Water Distribution in Gas Diffusion Layer of Polymer Electrolyte Fuel Cells by Synchrotron X-Ray Computed Tomography under Water Injection

Kato

Yamaguchi

Kato

et al. 2022

J. Chem. Eng. Japan / JCEJ

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As a rst step towards understanding the e ects of the local micro-structure of gas di usion layers (GDLs) on water accumulation in the GDL pores, ex situ X-ray computed tomography (XRCT) measurements were performed with a water injection device. When polymer electrolyte fuel cells are operated, the liquid water resulting from water vapor condensation adversely a ects their performance because the water clusters obstruct oxygen di usion. The water network constructed from XRCT images indicated that the water clusters could be categorized into three types: fully connected clusters, which started from the microporous layer (MPL) surface and reached the end side of the GDL substrate; MPLconnected clusters, which started from the MPL surface and were dead-ended; and isolated clusters, which did not connect either the MPL surface or the end side of the substrate. The results also suggested that many water paths were created in the substrate by branching, but that only a small portion of the water paths permeated the GDL. The methodology developed in this research is expected to be e ective in comparing GDLs with di erent manufacturing processes.

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“…The concept of using MPLs with large pores or perforations for a liquid water passage has been proven using synchrotron X-ray radiography and computed tomography by Hirai and co-workers, 30 Haußmann and co-workers, 31,32 and Nagai and co-workers. 33,34 Furthermore, Tang et al demonstrated that the introduction of a porosity gradient structure in the MPL using ammonium chloride resulted in the drainage of water that accumulated in the GDL. 35 The liquid water in hydrophobic pores flows from smaller pores to larger pores by capillary pressure.…”

Section: ■ Introductionmentioning

confidence: 99%

Managing the Pore Morphologies of Microporous Layers for Polymer Electrolyte Fuel Cells with a Solvent-Free Coating Technique

Yoshimune

Kato

Yamaguchi

et al. 2021

ACS Sustainable Chem. Eng.

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We report a solvent-free coating process for microporous layers (MPLs) in polymer electrolyte fuel cells to eliminate solvents, dispersing agents, and thickening agents of a conventional wet-coating process. In this environmentally friendly process, the MPLs were fabricated by depositing composite powder consisting of carbon and poly(tetrafluoroethylene) directly onto a fibrous carbon substrate using an electrostatic screen printer. This enables the fabrication of sufficiently sized MPLs for the cells of first-generation Toyota MIRAI fuel-cell vehicles. Microscopic observation of the surface and the cross sections of dry-coated MPLs revealed smooth defect-free surfaces. Static water contact angle measurements revealed the hydrophobicity of dry-coated MPLs to be equivalent to that of wet-coated MPLs. Moreover, the pore morphologies of dry-coated MPLs could be managed by controlling the particle arrangement by electrostatic screen printing. The particle and pore morphologies of dry-coated MPLs were characterized by mercury intrusion porosimetry and synchrotron X-ray computed nanotomography. From electrochemical characterizations for dry-coated MPLs, a porosity-graded MPL exhibits excellent flooding tolerance under operating conditions below the dew point, corresponding to 120% relative humidity. A multilayer obtained with the dry-coating process requires a single annealing process and has the necessary gradient features, thus potentially reducing the environmental impact of manufacturing next-generation fuel-cell vehicles.

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Ex-situ visualization of the wet domain in the microporous layer in a polymer electrolyte fuel cell by X-ray computed tomography under water vapor supply

Cited by 24 publications

References 34 publications

Discussion on Water Condensation in Membrane Pores during CO2 Absorption at High Temperature

Discussion on Water Condensation in Membrane Pores during CO2 Absorption at High Temperature

<i>Ex situ</i> Visualization and Network Analysis of Water Distribution in Gas Diffusion Layer of Polymer Electrolyte Fuel Cells by Synchrotron X-Ray Computed Tomography under Water Injection

Managing the Pore Morphologies of Microporous Layers for Polymer Electrolyte Fuel Cells with a Solvent-Free Coating Technique

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