Physically Based Modeling of PEMFC Cathode Catalyst Layers: Effective Microstructure and Ionomer Structure–Property Relationship Impacts

Randall, Corey Ryan; DeCaluwe, Steven C.

doi:10.1115/1.4046417

Cited by 10 publications

(12 citation statements)

References 54 publications

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“…This implies that data from SiO 2 studies may still provide useful insight into CCL Nafion. Some of the present authors have previously presented similar hypotheses, using water uptake and reduced species mobilities inferred exclusively from Nafion on SiO 2 (from ref ) in physics-based models to predict PEMFC performance as a function of Pt loading. , Outcomes showed excellent agreement with low-Pt-loaded PEMFC polarization data, indicating the suitability of majority layer Nafion on silicon supports as a reasonable surrogate for that in the PEMFC CCL.…”

Section: Discussionsupporting

confidence: 64%

“…However, DeCaluwe et al demonstrated that reduced mobility is still present in homogeneously hydrated majority layers . Furthermore, modeling work from Randall and DeCaluwe displayed good agreement to data from low-Pt-loaded PEMFCs when the models incorporated ionomer structure–property relationships assuming uniformly hydrated CCL Nafion at carbon interfaces. , …”

Section: Discussionmentioning

confidence: 94%

“…28 Furthermore, modeling work from Randall and DeCaluwe displayed good agreement to data from low-Ptloaded PEMFCs when the models incorporated ionomer structure−property relationships assuming uniformly hydrated CCL Nafion at carbon interfaces. 66,67 4.3. Nafion at Carbon vs Silicon Interfaces.…”

Section: Substrate-specific Nafion Interface Structuresmentioning

confidence: 99%

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Morphology of Thin-Film Nafion on Carbon as an Analogue of Fuel Cell Catalyst Layers

Randall,

Zou,

Wang

et al. 2024

ACS Appl. Mater. Interfaces

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Species transport in thin-film Nafion heavily influences proton-exchange membrane (PEMFC) performance, particularly in low-platinum-loaded cells. Literature suggests that phase-segregated nanostructures in hydrated Nafion thin films can reduce species mobility and increase transport losses in cathode catalyst layers. However, these structures have primarily been observed at silicon−Nafion interfaces rather than at more relevant material (e.g., Pt and carbon black) interfaces. In this work, we use neutron reflectometry and X-ray photoelectron spectroscopy to investigate carbon-supported Nafion thin films. Measurements were taken in humidified environments for Nafion thin films (≈30−80 nm) on four different carbon substrates. Results show a variety of interfacial morphologies in carbon-supported Nafion. Differences in carbon samples' roughness, surface chemistry, and hydrophilicity suggest that thin-film Nafion phase segregation is impacted by multiple substrate characteristics. For instance, hydrophilic substrates with smooth surfaces correlate with a high likelihood of lamellar phase segregation parallel to the substrate. When present, the lamellar structures are less pronounced than those observed at silicon oxide interfaces. Local oscillations in water volume fraction for the lamellae were less severe, and the lamellae were thinner and were not observed when the water was removed, all in contrast to Nafion−silicon interfaces. For hydrophobic and rough samples, phase segregation was more isotropic rather than lamellar. Results suggest that Nafion in PEMFC catalyst layers is less influenced by the interface compared with thin films on silicon. Despite this, our results demonstrate that neutron reflectometry measurements of silicon−Nafion interfaces are valuable for PEMFC performance predictions, as water uptake in the majority Nafion layers (i.e., the uniformly hydrated region beyond the lamellar region) trends similarly with thickness, regardless of support material.

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Section: Discussionsupporting

confidence: 64%

Section: Discussionmentioning

confidence: 94%

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Morphology of Thin-Film Nafion on Carbon as an Analogue of Fuel Cell Catalyst Layers

Randall,

Zou,

Wang

et al. 2024

ACS Appl. Mater. Interfaces

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“…Thus, many studies related to numerical simulation in the PEFCs have been reported. [4][5][6][7] Recently, a numerical analysis was performed on the electrochemical kinetics and mass transport inside porous materials. It was reported that the local saturation of liquid water, distribution of the electrochemical variables, and mass fraction of samples could be controlled by regulating the operating conditions.…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis on influence of surface structures of cathode catalyst layers on performance of polymer electrolyte fuel cells

Park

Wei

et al. 2022

Electrochemical Science Adv

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Because it is time‐consuming to optimize the design of a cathode catalyst layer (CCL), a numerical simulation to predict the reaction and mass transport characteristics without trial and error is desirable. This study used numerical analysis to investigate how the mass transport occurring in CCLs with flat and three‐dimensional (3D) structures influenced the performance. The simulations included the reconstruction of the CCLs and their electrochemical calculation using our multi‐block model. The simulation results showed the reduction of the proton resistance in the ionomer was a factor in improving the performance in the 3D structure in comparison with the flat structure. An increasing aspect ratio of the 3D structure improved the cell performance and decreased the proton resistance in the ionomer. These results were due to the shortened conductive path of the protons from the polymer electrolyte membrane to the gas diffusion layer side surface in the 3D structure. Finally, the cell performance with an increase in the ionomer content was predicted. This numerical analysis made it possible to understand the reaction of the 3D structure and mass transport and predict ways to optimize the structural design to improve cell performance.

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“…Toward this end, several recipes for catalyst ink dispersions have been tuned for optimum kinetic and thermodynamic performance [9][10][11][12][13][14]. The cathode of a high-power density PEMFC is typically made of a catalyst ink consisting of carbon black (C), forming an extensive skeleton.…”

Section: Introductionmentioning

confidence: 99%

On the State and Stability of Fuel Cell Catalyst Inks

Bapat

Giehl²,

Kohsakowski³

et al. 2021

Preprint

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Catalyst layers (CL), as an active component of the catalyst coated membrane (CCM), form the heart of the proton electrolyte membrane fuel cell (PEMFC). For optimum performance of the fuel cell, obtaining suitable structural and functional characteristics for the CL is crucial. Direct tuning of the microstructure and morphology of the CL is non-trivial; hence catalyst inks as CL precursors need to be modulated, which are then applied onto a membrane to form the CCM. Obtaining favorable dispersion characteristics forms an important prerequisite in engineering catalyst inks for large scale manufacturing. In order to facilitate a knowledge-based approach for developing fuel cell inks, this work introduces new tools and methods to study both the dispersion state and stability characteristics, simultaneously. Catalyst inks were prepared using different processing methods, which include stirring and ultrasonication. The proposed tools are used to characterize and elucidate the effects of the processing method. Structural characterization of the dispersed particles and their assemblages was carried out by means of transmission electron microscopy. Analytical centrifugation (AC) was used to study the state and stability of the inks. Herein, we introduce new concepts, S score, and stability trajectory, for a time-resolved assessment of inks in their native state using AC. The findings were validated and rationalized using transmittograms as a direct visualization technique. The flowability of inks was investigated by rheological measurements. It was found that probe sonication only up to an optimum amplitude leads to a highly stable colloidal ink.

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Physically Based Modeling of PEMFC Cathode Catalyst Layers: Effective Microstructure and Ionomer Structure–Property Relationship Impacts

Cited by 10 publications

References 54 publications

Morphology of Thin-Film Nafion on Carbon as an Analogue of Fuel Cell Catalyst Layers

Morphology of Thin-Film Nafion on Carbon as an Analogue of Fuel Cell Catalyst Layers

Numerical analysis on influence of surface structures of cathode catalyst layers on performance of polymer electrolyte fuel cells

On the State and Stability of Fuel Cell Catalyst Inks

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