Analysis of Catalyst Layer Microstructures: From Imaging to Performance

Sabharwal, Mayank; Pant, L. M.; Pütz, Andreas; Susac, Darija; Janković, Jasna; Secanell, Marc

doi:10.1002/fuce.201600008

Cited by 92 publications

(108 citation statements)

References 60 publications

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“…The liquid water concentration (cm 3 /g · carbon) reported by Deevanhxay et al 19 is converted to liquid water saturation by first subtracting the OCV water concentration (0.22 cm 3 /g · carbon), multiplying the result by the carbon density (1.9 g/cm 3 ) reported in Ref. 24 and finally multiplying by the ratio between solid phase (the carbon black only) and void phase.…”

Section: Resultsmentioning

confidence: 99%

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

Zhou

Stanier

Pütz

et al. 2017

J. Electrochem. Soc.

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The non-isothermal, two-phase membrane electrodes assembly numerical model previously developed in Part I [J. Electrochem. Soc., 164, 6, F530 (2017)] is validated by comparing to experimentally measured electrochemical performance data under various operating conditions. Water accumulation in catalyst layer (CL) and gas diffusion layer (GDL) are also compared to the neutron and X-ray imaging data and shown to be in agreement. Water fluxes at cathode and anode boundaries and phase change induced flow are analyzed and compared to experimental data. Simulation results indicate that when liquid water is present, reactant transport in the catalyst layer is the key factor limiting fuel cell performance. The model shows that at high relative humidity, 80 • C is the optimal operating temperature in order to delay water accumulation without degrading performance due to oxygen dilution by water vapor. The impact of CL and GDL hydrophilic volume fraction, hydrophobic contact angle and pore size distribution on performance are also studied. Results suggest that when liquid water is present, GDL parameters have minimal effect on performance and a CL should have a large hydrophobic contact angle, a low hydrophilic volume fraction, and large pore radius. Improving water management in polymer electrolyte fuel cell (PEFCs) is critical to achieving higher efficiency and power density, which are crucial for increasing range and reducing stack size, cost and weight in automobile applications. In order to understand water transport in PEFCs, develop improved water and heat management strategies, and design advanced gas diffusion layer (GDL), micro-porous layer (MPL) and catalyst layer (CL) micro-structures, advanced numerical models are required both at the macro-2 and micro-scales. 3Several two-phase, non-isothermal membrane electrode assembly (MEA) models have been developed over the past decades.4-8 A promising approach to include micro-structural details in MEA models has been the recent development of pore size distribution (PSD) based mathematical models for analyzing two-phase flow in porous electrodes models. 1,[9][10][11][12] In all previous work however, the PSD model was either not integrated in a complete membrane electrode assembly (MEA) model 9,11,12 or was integrated only in a one-dimensional model. 10,13 As a result, detailed validation of the numerical models has seldom been performed, and it has been mainly based on its capability to reproduce polarization curves 4,6,10 A two-dimensional model is required in order to study the validity of the water distribution in channel and land regions.In Reference 1, the authors introduced a mixed wettability pore size distribution based mathematical model for analyzing two-phase flow in porous electrodes. The pore size distribution and membrane electrode assembly models were validated by comparison to experimental polarization curves from literature data. The model however was not validated in terms of its ability to accurately estimate cell performance and cell resistance un...

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Section: Resultsmentioning

confidence: 99%

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

Zhou

Stanier

Pütz

et al. 2017

J. Electrochem. Soc.

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“…Benchtop x-ray tomography scanners are now widely available that can produce images with 1-μm voxel resolution, and the latest generation can obtain images with 100-nm resolution or lower [9,10]. Extracting the vast amount of information found in such images is an active pursuit [11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Versatile and efficient pore network extraction method using marker-based watershed segmentation

2017

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Obtaining structural information from tomographic images of porous materials is a critical component of porous media research. Extracting pore networks is particularly valuable since it enables pore network modeling simulations which can be useful for a host of tasks from predicting transport properties to simulating performance of entire devices. This work reports an efficient algorithm for extracting networks using only standard image analysis techniques. The algorithm was applied to several standard porous materials ranging from sandstone to fibrous mats, and in all cases agreed very well with established or known values for pore and throat sizes, capillary pressure curves, and permeability. In the case of sandstone, the present algorithm was compared to the network obtained using the current state-of-the-art algorithm, and very good agreement was achieved. Most importantly, the network extracted from an image of fibrous media correctly predicted the anisotropic permeability tensor, demonstrating the critical ability to detect key structural features. The highly efficient algorithm allows extraction on fairly large images of 500 3 voxels in just over 200 s. The ability for one algorithm to match materials as varied as sandstone with 20% porosity and fibrous media with 75% porosity is a significant advancement. The source code for this algorithm is provided.

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“…The PSD for the GDL microstructure was computed using the sphere fitting algorithm described in Ref. 73. The PSD algorithm first evaluates the distance transform at pore voxels in 3D, i.e., the distance of a pore voxel to the closest solid voxel.…”

Section: Theorymentioning

confidence: 99%

Virtual Liquid Water Intrusion in Fuel Cell Gas Diffusion Media

Sabharwal

Gostick

Secanell

2018

J. Electrochem. Soc.

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A cluster based full morphology (CFM) model is developed to predict liquid water intrusion in GDLs. The CFM model is used to simulate water intrusion into a dry GDL microstructure obtained from μ-CT. Numerical water saturation distributions are compared to experimental μ-CT reconstructions of the same GDL sample at varying saturation levels. A quantitative validation of the CFM model results is then provided by studying the number of voxels in the image that contain water in both the CFM model results and the μ-CT reconstructions. Results reveal that CFM simulations showed 56-95.7% agreement in the liquid water voxels when compared to the μ-CT simulations for saturations in the range of 29-92.3%. Gas transport simulations are then performed on μ-CT and CFM partially saturated GDLs in order to study the validity of the CFM model images to estimate transport properties of partially saturated GDLs. A maximum error of 20% was observed between the predicted effective diffusivities obtained from CFM simulations and those obtained directly from simulations on the μ-CT data for saturations below 40%. Effective diffusivity predictions from the CFM simulations agree well with in-plane effective diffusivities in literature while the through-plane effective diffusivities were underpredicted by a factor of 2.

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Analysis of Catalyst Layer Microstructures: From Imaging to Performance

Cited by 92 publications

References 60 publications

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

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

Versatile and efficient pore network extraction method using marker-based watershed segmentation

Virtual Liquid Water Intrusion in Fuel Cell Gas Diffusion Media

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