Effects of liquid water on the pore structure and transport coefficients in the cathode catalyst layer of PEM fuel cells

Dou, Shaojun; Hao, Liang; Liu, Hong

doi:10.1016/j.ijhydene.2022.09.187

Cited by 9 publications

(2 citation statements)

References 48 publications

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“…La CL consists of a void region, ionomer, and platinum carbon-supported catalyst (Pt/C) 20 . The transport phenomena and characteristics of the CL depend on the composite morphological structures, compositions and pore structure (closed pores and dead-end pores) 21,22 .…”

Section: Introductionmentioning

confidence: 99%

Theoretical analysis of the effect of isotropy on the effective diffusion coefficient in the porous and agglomerated phase of the electrodes of a PEMFC

Pacheco,

Barbosa,

Navarro-Montejo

et al. 2024

Preprint

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In polymer membrane fuel cells (PEMFC), the pore microstructure and the effective diffusion coefficient (\({D}_{eff}\)) of the catalytic layer have a significant impact on the overall performance of the fuel cell. In this wok, numerical methods to simulate PEMFC catalytic layers were used to study the effect of isotropy (\({I}_{xy}\)) on the \({D}_{eff}\). The proposed methodology studies reconstructed systems by Simulated Annealing (SA) imaging with different surface fractions of microstructures composed by two diffusive phases: agglomerates and pores. The \({D}_{Eff}\) is determined numerically by the Finite Volume Method (FVM) solved for Fick's First Law of Diffusion. The results show that the proposed methodology can effectively quantify the effect of isotropy on the \({D}_{eff}\) for both diffusion phases. Two trends were obtained in the magnitude of the \({D}_{eff}\) concerning the change in isotropy: a) when the surface fraction is more significant than 50%, the \({D}_{eff}\) decreases linearly at the beginning and exponentially at the end of the isotropy change, which indicates that small changes in isotropy in the particulate material modify it drastically. b) When the surface fraction is less than 50%, the \({D}_{eff}\) decreases exponentially at the beginning and linearly at the end of the isotropy change, which shows that small isotropy changes in the bar-aligned material drastically alter it. The proposed methodology can be used as a design tool to improve the mass transport in porous PEMFC electrodes.

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Section: Introductionmentioning

confidence: 99%

Theoretical analysis of the effect of isotropy on the effective diffusion coefficient in the porous and agglomerated phase of the electrodes of a PEMFC

Pacheco,

Barbosa,

Navarro-Montejo

et al. 2024

Preprint

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show abstract

“…They found that thick ionomer films are favorable to improve water and proton transport, while thin ionomer films enhance oxygen transport due to increased solubility in ionomer. Dou et al (2022) [29] investigated the effect of capillary condensation on effective oxygen diffusivity and proton conductivity using LBM. They concluded that oxygen blockage by liquid water can be significantly suppressed with hydrophobic CLs.…”

Section: Introductionmentioning

confidence: 99%

A Numerical Assessment of Mitigation Strategies to Reduce Local Oxygen and Proton Transport Resistances in Polymer Electrolyte Fuel Cells

García-Salaberri

2023

Materials

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The optimized design of the catalyst layer (CL) plays a vital role in improving the performance of polymer electrolyte membrane fuel cells (PEMFCs). The need to improve transport and catalyst activity is especially important at low Pt loading, where local oxygen and ionic transport resistances decrease the performance due to an inevitable reduction in active catalyst sites. In this work, local oxygen and ionic transport are analyzed using direct numerical simulation on virtually reconstructed microstructures. Four morphologies are examined: (i) heterogeneous, (ii) uniform, (iii) uniform vertically-aligned, and (iv) meso-porous ionomer distributions. The results show that the local oxygen transport resistance can be significantly reduced, while maintaining good ionic conductivity, through the design of high porosity CLs (ε≃ 0.6–0.7) with low agglomerated ionomer morphologies. Ionomer coalescence into thick films can be effectively mitigated by increasing the uniformity of thin films and reducing the tortuosity of ionomer distribution (e.g., good ionomer interconnection in supports with a vertical arrangement). The local oxygen resistance can be further decreased by the use of blended ionomers with enhanced oxygen permeability and meso-porous ionomers with oxygen transport routes in both water and ionomer. In summary, achieving high performance at low Pt loading in next-generation CLs must be accomplished through a combination of high porosity, uniform and low tortuosity ionomer distribution, and oxygen transport through activated water.

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Effects of agglomerate structure and operating humidity on the catalyst layer performance of PEM fuel cells

Dou,

Hao,

Wang

et al. 2024

Applied Energy

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Effects of liquid water on the pore structure and transport coefficients in the cathode catalyst layer of PEM fuel cells

Cited by 9 publications

References 48 publications

Theoretical analysis of the effect of isotropy on the effective diffusion coefficient in the porous and agglomerated phase of the electrodes of a PEMFC

Theoretical analysis of the effect of isotropy on the effective diffusion coefficient in the porous and agglomerated phase of the electrodes of a PEMFC

A Numerical Assessment of Mitigation Strategies to Reduce Local Oxygen and Proton Transport Resistances in Polymer Electrolyte Fuel Cells

Effects of agglomerate structure and operating humidity on the catalyst layer performance of PEM fuel cells

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