bluuebunny/crossref_metadata_2025 huggingface dataset:
A Machine Learning Accelerated Hierarchical 3D+1D Model for Proton Exchange Membrane Fuel Cells
Authors: Pan Yuwei , Ruan Haijun , Regmi Yagya N , Wu Billy , Wang Huizhi , Brandon Nigel
Published: February 2024

Physics-based continuum models for proton exchange membrane fuel cells (PEMFCs) are an essential tool for fuel cell design and management. To date, many continuum models, ranging from 1D to 3D, have been developed for PEMFCs. Although computationally efficient, 1D models do not account for heterogeneity in flow fields, which negatively impact their accuracy. In contrast, 2D and 3D models are usually more representative of actual operating conditions but computationally intensive due to the coupled partial differential equations and large number of mesh elements involved. To overcome these issues, a hierarchical approach that combines a 2D/3D description of flow fields, gas diffusion layers (GDLs) and a simplified microporous layer (MPL)/catalyst layer (CL)/membrane sub-model has been proposed in the literature. However, studies based on this method often use a simplified or 0D MPL/CL/membrane sub-model, whose results may deviate from a full 1D description due to the neglected nonlinearity, especially at higher loads.

In this study, we present a computationally efficient 3D+1D hierarchical model for PEMFCs accelerated by machine learning. The 3D model, which captures the two-phase flow in the gas channels and GDLs, is coupled with a full 1D description of the MPLs, membrane, CLs, and CL agglomerates by exchanging boundary values and fluxes, as shown in the figure. To avoid the high computing cost increase associated with the full 1D description, we develop a physics-informed neural network to replace the 1D sub-model for coupling with the 3D model, while maintaining the full description of fuel cell internal states. Large synthetic datasets are generated using the 1D model for training the neural network, ensuring the accuracy of the model. The proposed 3D+1D model is validated against experimentally obtained polarization curves and high frequency resistances under different relative humidities. The proposed model is then used to study the nonlinear distribution of the internal states along the thickness direction of the membrane electrode assembly as well as in the 3D flow field. The model is also highly effective in elucidating the dominant voltage loss factor under different operating conditions. Our developed model offers high accuracy at low computing cost under a wide range of operating conditions, potentially aiding the rapid optimization of both the membrane electrode assembly and the gas channel geometry and advance the water and thermal management of existing fuel cell designs.

Figure 1
Numerical Simulation of Liquid Water Behavior in PEFCs with Different GDL Wettability
Authors: Naito Hiroshi , Hirai Shuichiro
Published: February 2024

The performance of polymer electrolyte fuel cells (PEFCs) is greatly influenced by internal transport phenomena. Particularly, accumulation of liquid water due to electrochemical reaction is one of the main factors that prevents the transport of oxygen and increases the concentration overpotential, and thus, quick rejection of liquid water accumulation is important issue for improving performance. This study focuses on liquid water accumulation inside gas diffusion layers (GDLs), and investigates how wettability of the substrate surface alters the liquid water behavior using numerical simulation. In this study, a numerical simulation incorporating condensation phenomena was performed using three-dimensional structure of GDL substrate obtained from CT measurements. The cell temperature and the current density were set to 40° and 0.6A/cm2, and the contact angles of the substrate was set to 60°, 110°, 150°. The simulation results showed that in the hydrophobic cases of 110°, 150°, the droplets began to move between pores to minimize their surface energy as their size grew into pore scale of the substrate. While in the hydrophilic 60° case, the liquid water condensed near the catalyst layer only moved in such a way that the thickness of the liquid water increased, and no droplet-like structure were observed. In the 150° case, the contact area between the substrate and the droplets was smaller than that in the case of 110°, and the surface energy of the droplets was assumed to be larger. It was found that the liquid water accumulation is highest at the 60° case followed by 110°, 150°.

Figure 1
Capturing the Microstructural Complexities of PEMFC Catalyst Layers and Local Transports Therein Using Network Modeling Approach
Authors: Alam Shahriar , Allen Jeffrey S
Published: February 2024

The microstructural characteristics of the catalyst layer are critical for understanding the effect of local transport processes (water, reactant gas, and proton transport) in catalyst layers on overall PEMFC performance. Here, we present a network architecture that uses structured networks to capture the morphological heterogeneity of PEMFC catalyst layers. Using the poroelastic theory of swelling, it depicts how the ionomer within the catalyst layers absorbs water and expands in volume with respect to humidity which dictates the shift in porosity and pore size distribution of the catalyst layers. Local transport behavior (flooding, reactant gas, and proton starvation at the reaction sites) under different PEMFC operating conditions are analyzed by applying transport equations to the generated networks.
Influence of Ionomer Chemistry on Oxygen Permeability in Hydrocarbon-Based Proton-Exchange Membrane Fuel Cells
Authors: Liepold Hannes , Nguyen Hien , Münchinger Andreas , Vierrath Severin
Published: February 2024

The pursuit of alternatives to perfluorinated sulfonic acid (PFSA) materials is of particular interest in light of the global and European mid-term goals to avoid fluorinated materials, and the technical target to operate proton-exchange membrane (PEM) fuel cells at temperatures of 120°C. Non-fluorinated hydrocarbon ionomers offer improved chemical stability at temperatures above 100°C, are less environmentally hazardous, exhibit lower gas crossover, and have the potential to reduce production costs.1 Recent years have seen significant progress in the development of hydrocarbon-based membranes and electrodes, with performance on par with that of state-of-the-art PFSA-based fuel cells under optimized conditions.2 However, a performance gap between hydrocarbon- and PFSA-based PEM fuel cells persists under application-relevant conditions, necessitating an understanding of the limitations that arise. Mass transport-related phenomena, particularly at the ionomer/catalyst interfaces, play a crucial role in controlling PEM fuel cell performance.3 While extensive studies have been conducted for PFSA-based fuel cells to deconvolute the local from the total transport resistance of the cathode catalyst layer, no such studies have been conducted for hydrocarbon ionomers. In this study, we investigated gas transport resistance and its components in hydrocarbon-based PEM fuel cells using H2- and O2 limiting current methods and ex-situ investigations in ionomer thin film behavior, while varying the ionomer's ion-exchange capacity. Our results show that local transport resistances are similar to those measured with PFSA-based cells with respect to different ionomer to carbon mass ratios (I/C). However, higher transport-induced resistances are observed under the potential formation of liquid water in the range of high current densities. We attribute these effects to the more pronounced water uptake of the ionomer thin film compared to the PFSA based reference. Thus, reducing ionomer swelling while maintaining the necessary proton conductivity of the ionomer thin film is crucial for next-generation hydrocarbon PEM fuel cells.

References

(1) H. Nguyen, C. Klose, L. Metzler, S. Vierrath and M. Breitwieser, Adv.
Energy Mater., 2022, 12, 2103559.

(2) H. Nguyen, F. Lombeck, C. Schwarz, P. Heizmann, M. Adamski, H. F. Lee, B. Britton, S. Holdcroft, S. Vierrath and M. Breitwieser, Sustainable Energy Fuels, 2021, 5, 3687–3699.

(3) T. Schuler, A. Chowdhury, A. T. Freiberg, B. Sneed, F. B. Spingler, M. C. Tucker, K. L. More, C. J. Radke and A. Z. Weber, J. Electrochem. Soc
., 2019, 166(9), F3020.
(Poster Award - Honorable Mention) Probing the Catalyst-Ionomer Interface in Catalyst Layers with Sulfo-Phenylated Polyphenylene Ionomers Using CO-Displacement and Stripping Techniques
Authors: Anton Robert James , Sun Shikai , Swider-Lyons Karen , Mittelsteadt Cortney , Adamski Michael , Britton Benjamin , Morimoto Yu , Zenyuk Iryna
Published: February 2024

Sulfo-phenylated polyphenylene ionomers (sPPP) are a class of hydrocarbon Ionomer being explored as a replacement for the perfluorinated sulfonic acid (PFSA) ionomer in fuel cell membranes and catalyst layers because they do not contain fluorinated compounds. Integration of sPPP ionomers into catalyst layers is challenging, as they have significantly different morphology compared to PFSA-based ionomers. Furthermore, little is known about the resulting ionomer-catalyst interface and whether characterization techniques developed for catalysts layers with PFSA-based ionomers will perform well for catalyst layers containing an sPPP ionomer. In this work, we examine the usefulness of CO displacement and stripping techniques to probe both the electrochemically active surface area (ECSA) of Pt/C in the catalyst layer and adsorbed species on the Pt catalyst sites. For catalyst layers containing PFSA, we measure a strong CO displacement reduction peak at potentials above potential of zero charge, when CO is introduced to the system, corresponding to sulfonic acid groups being displaced from active sites. The range of sulfonic acid groups adsorbed on the surface is 15- 25 % depending on the carbon support used. When the catalyst layers contain an sPPP ionomer instead of PFSA, the CO displacement peak is almost entirely suppressed, resulting in less than 10 % of sulfonic acid group adsorption. This is indicative that sPPP ionomer orientation near the Pt surface is very different compared to PFSA-based ionomer and that sulfonic acid groups do not “poison” Pt when in contact with the sPPP ionomer. However, mass activity increase is not observed for the sPPP ionomer-based catalyst layers, indicating there might be different “poisoning” mechanisms present, perhaps associated with the phenyl rings adsorption [1]. ECSA measurements for MEAs containing the non-fluorinated ionomer catalyst layers align with those measured for PFSA MEAs with the same catalysts type, loading, and comparable ionomer content, indicating that CO stripping is still a useful tool for assessing the ECSA for MEAs.

[1] Zhai, Y., Baturina, O., Ramaker, D., Farquhar, E., St-Pierre, J., & Swider-Lyons, K. (2015). Chlorobenzene Poisoning and Recovery of Platinum-Based Cathodes in Proton Exchange Membrane Fuel Cells. Journal of Physical Chemistry C, 119(35), 20328–20338. https://doi.org/10.1021/acs.jpcc.5b06362
Localized Study of the CCM with Graded Ionomer and Catalyst Loading across the X-Y and Z Directions Using Current Scan Shunt
Authors: Choi Yejung , Fortin Patrick
Published: February 2024

In project CAMELOT, it is aimed to diagnose the fundamental transport properties that limit performance in state-of-the-art (SoA) and prototype beyond-SoA Membrane Electrode Assembly (MEA)s and materials. To accomplish this goal, a series of in-situ characterization methods are used to create correlations between the observed performance, voltage loss breakdowns at the cell level, and the fundamental material property characteristics of the MEA and MEA materials. To accomplish this goal, thin Catalyst Coated Membrane (CCM) with low Pt loading is used as target study material; and the logic for using thinner layers in each of the MEA components is clear: thinner constituent layers (membrane, catalyst layers, microporous layers (MPL), gas diffusion layers (GDL)) means shorter transport distances for protons, oxygen, hydrogen and electrons and should thus reduce the associated transport losses. Thin‐layer X‐Y and Z direction graded catalyst layers are developed in project CAMELOT to optimize porosity, ionomer content and catalyst loading across the X‐Y and Z directions of the CCM. For the X‐Y direction CAMELOT matches the catalyst layer composition to the conditions at different locations within the flow field. For example, the porosity and ionomer content of the catalyst layer near the outlet of the flow field should be tuned for significantly wetter conditions than at the flow field inlet. For Z direction CAMELOT matches the catalyst layer composition to the conditions of the membrane and the GDL layer. The goal is to ensure that at each point in the active area, the catalysts can operate as close to their maximum (kinetically limited) performance as possible by minimizing mass transport limitations under the conditions that prevail at the different locations. For example, the porosity and ionomer content of the catalyst layer near the outlet of the flow field should be tuned for significantly wetter conditions than at the flow field inlet. Current Scan Shunt (CSS) is used as a convenient tool to measure real-time current density and temperature distribution within the fuel cell in situ operando, to analyze the cell behavior depending on the components and the direction of the grading catalyst layer on the developed CCMs. The experimental work will later be supplemented by a theoretical analysis carried out in the modelling work and, together, the modelling and experimental analysis can be used to construct a complete picture of correlated relationships between the MEA structure and properties and the associated voltage loss causes of the performance limitations for current SoA materials.
The Porous Structure Design of Catalyst Layer by Controlling Particle Size Distribution of PEMFC Catalyst Ink
Authors: Cho Minju , Cho Sung Yong , Cho Youngick , Lee Ji-Eun , Lee Sungchul , Park Eun-Byeol , Kim Young-Min , Kang Eun Heui
Published: February 2024

A general catalyst ink of proton exchange membrane fuel cells(PEMFC) consists of a catalyst, its support, an ionomer, and a solvent. These elements are made in the form of membrane electrode assembly(MEA) through grinding, dispersing, and coating processes. Therefore, the preparation of catalyst ink is an important step that directly affects the structure formation of the catalyst layer and the cell performance.

In this study, by controlling the particle size distribution of the catalyst ink, we aim to achieve optimized pore structure in the catalyst layer that leads to improved performance of the fuel cell. Particle size and its distribution of the catalyst ink were confirmed by using particle size analyzer(PSA). Mercury intrusion porosimetry(MIP) was used to determine porous structure, including the pore diameter and total pore volume of MEA. Segmented tomographic evaluation is utilized to evaluate the 3D porous carbon structure in terms of local surface area, pore size distribution, and their 3D networking. MEA were tested to ascertain the influence of the catalyst ink properties on electrochemical character such as H2/air polarization curves, electrochemical impedance spectroscopy(EIS). Also, to analyze the resistance contributed by the molecular and Knudsen diffusion and permeation through the ionomer film, we tested MEA using limiting-current measurements.

As a result, We are able to confirm that the particle size has a high correlation with the pore characteristics of the electrode layer that affect the cell performance. The enhanced electrochemical performance is attributed by decreasing fine particles about 0.1um in size. We figured out that the gas diffusion resistance in the catalyst layer increases as the fine particles increase. The results of this study will provide important insights into the design and fabrication of the catalyst layers in PEMFCs and could potentially lead to improvements in the efficiency of fuel cells.
Observation of Catalyst Layer Structure Formation from Electrode Slurry By White Light Confocal Microscopy
Authors: Suzuki Takahiro , Kirigaya Ryo , Tsushima Shohji
Published: February 2024

Mass transport in the catalyst layers (CLs) is an important factor to improve the cell performance of polymer electrolyte fuel cells (PEFCs). Transport properties in the CLs are determined by their structure and material distributions. The CLs are usually fabricated from electrode slurry in which Pt/C and ionomer are contained through applying and drying processes. Therefore, the structure and material distributions in the CLs are determined in these fabrication processes. However, these fabrication processes have been developed through trial-and-error approaches. A fundamental understanding of the structure formation mechanisms during the fabrication processes is required.

The authors have performed impedance measurement and surface displacement measurement of electrode slurry during the drying process at the same time and detected the particle packing process (1, 2). For a further understanding of the fabrication process, observation of the structure formation of electrode slurry during drying by white light confocal microscopy was conducted in this study to break down the structure formation regimes. The observation of flow mode on the surface of the slurry and measurement of surface displacement were performed at the same time.

Figure 1 shows confocal images of the electrode slurry during drying. Three different regimes were observed. At the initial state of drying, convection flow was observed. Then, the shrinking of the slurry was observed. After shrinking stopped, the solvent was evaporated from the porous media and finally, the structure of the catalyst layer was formed. Understanding the relationships between the variation of the flow regimes during the drying of electrode slurry and fabrication conditions including materials and process parameters can contribute to revealing the methodology for controlling porous structure and material distributions in the catalyst layers.

Acknowledgments

A part of this work was supported by JST PRESTO JPMJPR22O4.

References

(1) T. Suzuki et al., ECS Trans., 67(17), 465 (2015).

(2) T. Suzuki et al., J. Therm. Sci. Technol., 16(1), 20-00259 (2021).

Figure 1
Analysis of Transmission Line Models for PEMFC Impedance Modelling
Authors: Schwab Kersten , Weber Andre
Published: February 2024

The behaviour of Polymer Electrolyte Membrane Fuel Cells (PEMFC) shows a complex, non-linear dependence on material properties and operation conditions. Therefore, modelling and model parameterization by electrochemical characterization of PEMFCs is challenging. To deconvolute the different loss mechanisms in PEMFCs, impedance spectra are recorded and modelled by equivalent circuit models. Transmission Line Models (TLMs) are a well-established, physicochemical approach for modelling the impedance of PEMFC electrodes. TLMs consider the processes occurring in an electrode and the model parameters are directly related to material and microstructural characteristics. PEM electrodes have inhomogeneous distributions of the material, the current density, stored water, etc. Assuming a homogeneous electrode with homogeneous current distribution, the basic TLM shown in [1] turned during impedance fitting out to be inaccurate in operation conditions where these assumptions do not hold.

To increase the fit accuracy, literature proposes a number of adapted TLMs. These TLMs have additional components and therefore degrees of freedom. This enables these models to take additional processes and the microstructure into consideration.

In this contribution an incremental 1 cm² PEMFC ensuring zero gradient operation is characterized by means of impedance spectroscopy. Different operating conditions are varied within wide ranges and additional characterization methods, like H2/N2 operation were applied.

Different TLMs proposed in literature are evaluated by fitting them to the measured spectra with and without considering the information gained from additional measurements. The DRT was applied as additional criteria in the fitting.

In general, the accuracy of a fit increased with the number of free fitting parameters. Thus more complex TLMs accounting for additional physicochemical processes provide a lower error in the fit. Nevertheless the physicochemical meaningfulness of the determined model parameters is sometimes uncertain. It will be shown that for a meaningful parameterization by CNLS-fitting such TLMs require additional tests and characterization methods.

[1] Heinzmann Marcel; Weber André; Ivers-Tiffée Ellen. „Impedance modelling of porous electorde structures in polymer electrolyte membrane fuel cells“. In: Journal of Power Sources (2019).
(Invited) Characterization of PEM Fuel Cell Catalyst Layers – from Powder to End of Life
Authors: Zamel Nada , Schneider Patrick , Ney Linda , Gerteisen Dietmar , Hadrich Anne-Christine , Hou Yuze
Published: February 2024

Increasing the long-term stability of polymer electrolyte membrane fuel cells in general and under dynamic operation, in particular, is crucial for its commercialization. This stability is not only affected by operation parameters, but also the components and their design. In this talk, we discuss our ongoing activities at Fraunhofer ISE to fully understand the cell’s behavior and stability through experimental and numerical methods. To do so, the catalyst layers are produced in house and characterized through a fully automated and standardized protocol. Hence, we look at the effect of catalyst layer design on the overall life of the cell. In this talk, we will discuss the ageing of catalyst layers in relation to their design using both in-situ and ex-situ experimental analysis as well as numerical modeling.
Grooved Electrodes for High Power Density Fuel Cells
Authors: Lee ChungHyuk , Kort-Kamp Wilton , Yu Haoran , Cullen David A. , Patterson Brian M. , Arman Tanvir Alam , Komini Babu Siddharth , Mukundan Rangachary , Borup Rod L. , Spendelow Jacob S.
Published: February 2024

Proton exchange membrane fuel cells (PEMFCs) are a promising alternative to internal combustion engines, owing to their intrinsic power density, decoupled energy storage and generation, and relatively short refueling time. However, challenges related to cost, performance, and durability continue to prevent wide adoption of PEMFCs.1 Development of alternative electrode structures, which can enable smaller and less expensive PEMFCs with higher power and lower precious metal content, provides a promising path to overcome these challenges.2 Here, we report grooved electrodes, where the transport pathways of H+ and O2 were partitioned. Specifically, H+ are transported through electrode ridges with optimized ionomer content, and O2 is transported through the grooves that separate the electrode ridges. The grooved electrodes made with commercial electrode materials enhanced the performance up to 50%, and the enhancement becomes greater after accelerated durability tests. We verify via electrochemical impedance analyses, limiting current measurements, and multiphysics modeling that the enhancement is due to improved H+ and O2 transport. The work also demonstrates that the electrodes can be further improved by optimizing the electrode geometry, proven via machine learning investigations. These results inform next generation electrode designs for enhanced PEMFC performance and durability.

Acknowledgement:

This work was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos. Financial support for this work from the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory (LANL) is gratefully acknowledged (Projects 2020200DR and 20210915PRD2). ChungHyuk Lee acknowledges the support of the Natural Sciences and Engineering Research Council of Canada (NSERC).

References:

D. A. Cullen et al., Nat. Energy, 6, 462–474 (2021).

K. Jiao et al., Nature, 595, 361–369 (2021).
Mass Transport Impedance in a PEMFC with Superhydrophobic Catalyst Layers
Authors: Duque Luis , Molinero Antonio , Oller Juan Carlos , Barcala José Miguel , Díaz-Álvarez Ester , Folgado M. Antonia , Chaparro Antonio M
Published: February 2024

Electrosprayed catalyst layers improve liquid water management in PEMFCs thanks to their superhydrophobic character [1]. Using appropriate parameters, the electrospray deposition of a suspension of Pt/C powder and ionomer (Nafion solution) gives rise to a macroporous layer with superhydrophobic pores. Under current generation in a PEMFC, superhydrophobicity of the cathodic catalyst layer minimizes water interaction with pores walls, and enhances water transport towards the anode. As a consequence, water distribution inside the cell is more homogeneous, which makes cathode flooding less severe and improves anode humidification. PEMFCs with cathodic electrosprayed catalyst layer have shown higher power production rate at intermediate and high current densities, with peak power densities above 20%-25% compared with conventional, more hydrophilic, catalyst layer under standard testing conditions. We have studied in previous works the transport properties of electrosprayed catalyst layers with a number of techniques, like polarization curves, electrochemical impedance spectroscopy, and hydrogen transport.

In this communication, catalyst layer transport properties in a PEMFC with electrosprayed electrodes are studied with 'Current Modulated Hydrogen Flow Rate Spectroscopy' (CH2S) [2], which is a transport impedance technique relating hydrogen flow rate with faradaic current. With this aim, PEMFCs have been mounted with electrosprayed catalyts layers in anode and in cathode. When in anode, the electrosprayed catalyst layer gives rise to significant differences in the CH2S Nyquist plots and dependent on cell humidification (Fig. 1). The CH2S signals resolve transport kinetics having different characteristic times, that can be assigned to transport in different parts of the anode, like flow-field, gas diffusion layer, microporous layer and catalyst layer. The study is completed with CH2S measurements on PEMFCs with different configurations, having electrosprayed electrodes in anode and cathode. It is concluded that CH2S provides new insights into mass transport properties of gas diffusion electrodes.

Acknowledgements

Funding by PORHYDRO2 project (TED2021-131620B-C22, ‘Preparation and characterisation of catalyst layers fabricated by electrospray for proton exchange fuel cells with passive gas feed’) by the Spanish Ministry of Science and Innovation.

[1] M.A. Folgado, J.J. Conde, P. Ferreira-Aparicio, A.M. Chaparro, Single Cell Study of Water Transport in PEMFCs with Electrosprayed Catalyst Layers, Fuel Cells. 18 (2018) 602–612. https://doi.org/10.1002/fuce.201700217.

[2] L. Duque, A. Molinero, J.C. Oller, J.M. Barcala, M.A. Folgado, A.M. Chaparro, Analysis of Hydrogen Feeding to the Anode of a PEMFC By a Transport Impedance Technique, ECS Meet. Abstr. MA2022-02 (2022) 1406–1406. https://doi.org/10.1149/ma2022-02391406mtgabs.

Figure 1
Characterization of Catalyst Layer Using Gas Diffusion Electrode Half-Cell System for High Temperature Polymer Electrolyte Membrane Fuel Cell
Authors: Jung Hyeon Seung , Kim Dong Hee , Kim Jong Gyeong , Pak Chanho
Published: February 2024

High-temperature polymer electrolyte membrane fuel cell (HT-PEMFC) is being developed for the heavy-duty vehicle which requires high power density and operation under extreme conditions. Conventional HT-PEMFC using phosphoric acid (PA) immersed PBI membranes and polytetrafluoroethylene (PTFE) binder faced issues such as unstable durability and low performance of membrane electrode assembly (MEA) due to PA leakage and uneven distribution within the catalyst layer.

In recent years, ion-pair membranes and ionomers for high temperatures have been developed, which can reduce PA leakage in MEA and improve ionic conduction within the catalyst layer. Incorporation of a new material into the MEA requires further research to enhance electrode design, catalyst utilization, and performance for the appropriate ionomer, as this material exhibits different characteristics from the conventional PTFE binder.

In this study, various gas diffusion electrode (GDE) was fabricated with the new ionomer, and GDE half-cell setups were introduced for rapid and efficient characterization of performance in the oxygen reduction reaction. This system serves as an intermediate step between rotating disk electrodes and single cells, providing a powerful tool for quickly screening and evaluating GDEs using small amounts of catalyst. Recent publications from Wilkinson [1] and Gasteiger [2] groups reviewed this new system, proposed new measurement protocols, and suggested improvements. Accordingly, GDE half-cell setups are designed to simulate HT-PEMFC operating conditions at 150 ℃ temperature with 85 wt.% PA electrolyte.

Electrochemical characteristics were evaluated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) following the protocols in previous papers with GDE half-cell. Resistance values obtained through EIS were further differentiated by peaks and frequency-based responses through the distribution of relaxation times transformation. Performance comparison between GDEs was carried out by measuring the voltage at 0.2 A/cm² and peak power density at 150 ℃, simulating a single cell-like environment. GDEs were fabricated with variables such as Pt loading, thickness, and porosity. And their physical properties were confirmed through mercury intrusion porosimetry and scanning electron microscopy. Ultimately, the study elucidated the correlation between the electrochemical data and physical properties.

References

[1] B.A. Pinaud, A. Bonakdarpour, L. Daniel, J. Sharman, D.P. Wilkinson, Key considerations for high current fuel cell catalyst testing in an electrochemical half-cell, J. Electrochem. Soc. 164 (2017) F321–F327.

[2] T. Lazaridis, B.M. Stühmeier, H.A. Gasteiger, H.A. El-Sayed, Capabilities and limitations of rotating disk electrodes versus membrane electrode assemblies in the investigation of electrocatalysts, Nat. Catal. 5 (2022) 363–373.
Quantifying Sheet Resistance and in-Plane Electrical Resistivity of PEM Water Electrolyzer Components
Authors: Utsch Nikolai , Berg Florian , Scheepers Fabian , Holtwerth Sebastian , Shviro Meital , Lehnert Werner , Mechler Anna K.
Published: February 2024

PEM water electrolysis is a promising technology for renewable hydrogen production. However, improving the performance and efficiency of PEM water electrolyzers requires a thorough understanding of the properties and behavior of their components. Here we present a robust and effective method for determining the sheet resistance of porous electrodes commonly used in technologies such as PEM water electrolyzers. For this, a new analysis method was developed that relies on industrial printed circuit boards, allowing resistance measurements at ten different length scales ranging from 250 µm to 2500 µm and a 1D mapping of the resistance at each length scale. The sheet resistance of a commercially available reference material is characterized in order to validate the method, and the impact of compression force on the probe-sample contact is demonstrated. Furthermore, the sheet resistance of commonly used PEM water electrolyzer components is investigated. This includes the discussion of the gas diffusion layer, porous transport layer, and catalyst layers coated onto a membrane. Besides, by using an image processing-based method, the thickness distribution of the catalyst layers can be obtained and is correlated with the electrical in-plane resistivity. The results indicate that the sheet resistance is a more relevant parameter than the in-plane electrical resistivity to characterize catalyst layers. We will present a ranking of different PEM water electrolyzer components according to their sheet resistance for both anode and cathode catalyst layers.

Acknowledgement

This project has received funding from the European Union's Horizon 2020 research and innovation programme under the PROMET-H2 grant agreement No 862253.
Quantifying Spatiotemporal Heterogeneity within Fuel Cells Using Simultaneous Neutron and X-Ray Tomography (NeXT)
Authors: Shrestha Pranay , LaManna Jacob Michael , Fahy Kieran , Kim Junseob , Lee ChungHyuk , Lee Jason Keonhag , Baltic Eli , Hussey Daniel Seth , Jacobson David , Lytle Spencer , Bazylak Aimy
Published: February 2024

Heterogeneity within electrochemical devices, such as fuel cells, influences their performance and durability in ways that are not fully understood. 4-dimensional (4-D; 3 spatial dimensions and time) operando visualization techniques such as X-ray (1-2) and neutron (3) tomography are powerful tools to probe heterogeneity within operating electrochemical devices in high spatiotemporal resolution. Combining neutron and X-ray tomography (NeXT) (3-4) simultaneously offers unique advantages over single-modality methods, especially in terms of enhanced contrast between materials. There is a significant opportunity to utilize NeXT to characterize and quantify heterogeneity within electrochemical devices during cell operation. In this study, we utilize quantitative NeXT to identify spatiotemporal heterogeneity in the morphology of the membrane electrode assembly (MEA) and water distribution within the porous layers and the membrane. A custom interfacial tracking algorithm is utilized to accurately characterize 4-D morphology and boundaries of cell components. Heterogeneity is found to depend upon location with respect to cell components and operating conditions (such as current density and inlet relative humidity). Variations in the MEA morphology is dominated by variations in membrane morphology, whereby variations of up to 80 μm is observed in membrane thickness for N117 membranes (Chemours, USA). We find that the interface between the gas diffusion layer and the enclosing gasket is a high porosity region that accumulates liquid water during cell operation, and this liquid accumulation leads to high membrane hydration and membrane swelling near the interface. With this study, we demonstrate the viability of quantitative NeXT to characterize operando heterogeneity within multi-component electrochemical devices, taking us a step closer towards rational control and design of inherent heterogeneity within these devices. References 1. Y. Singh, R. T. White, M. Najm, T. Haddow, V. Pan, F. P. Orfino, M. Dutta, and E. Kjeang, J. Power Sources., 412 (2019): 224-237. 2. Xu, Hong, Minna Bührer, Federica Marone, Thomas J. Schmidt, Felix N. Büchi, and Jens Eller, J. Electrochem. Soc., 168, no. 7 (2021): 074505. 3. J. M. LaManna, Y. Yue, T. A. Trabold, J. D. Fairweather, D. S. Hussey, E. Baltic and D. L. Jacobson, Meet. Abstr. - Electrochem. Soc., 32 (2017). 4. Shrestha, Pranay, Jacob Michael LaManna, Kieran Fahy, Junseob Kim, ChungHyuk Lee, Keonhag Keonhag Lee, Eli Baltic, David Jacobson, Daniel Hussey, and Aimy Bazylak, Meet. Abstr. - Electrochem. Soc. 242, no. 39, pp. 1451-1451 (2022).
Structure, Ionomer and Water Distribution in Catalyst Layer of Proton Exchange Membrane Fuel Cell
Authors: Morin Arnaud , Chabot Florian , Porcar Lionel , Rosini Sébastien
Published: February 2024

Catalyst layer’s (CL) ionomer plays a crucial role in the operation of Proton Exchange Membrane Fuel Cell (PEMFC), not simply because it binds the catalyst nanopowder but mostly because it allows proton transport and affects both gas diffusivity and water management [1]. In the CL, the ionomer is a perfluorosulfonic acid polymer similar to that use in the membrane as electrolyte. It is in the form of a few nanometer thick film dispersed around the carbon support or as aggregates larger than 150 nm within the pores of the carbon network [2,3]. In contrast with bulk ionomer membrane or model thin films that have been extensively studied, still little is known on the distributions of ionomer, and especially of water, within the catalyst layer upon hydration [4]. However, this information is crucial to understand the operation and degradation of PEMFC.

In the frame of the project FURTHER-FC [5], we perform extensive analysis of the water sorption properties, and in a more unusual way, of the structure of the catalyst layer as a function of relative humidity for different types of carbon support, using Small Angle Neutron Scattering (SANS). It allows us to estimate qualitatively the distribution of the ionomer, and to quantify the average thickness of the ionomer film coating the catalyst, as well as the location of water within the CL upon hydration.

The project FURTHER-FC [2] has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking (now Clean Hydrogen Partnership) under Grant Agreement No 875025. This Joint Undertaking receives support from the European Union’s Horizon 2020 Research and Innovation program, Hydrogen Europe and Hydrogen Europe Research.

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Morawietz, T. et al., Fuel Cells 18, 239–250 (2018)

Kusoglu et al., Chem. Rev. 117, 987−1104 (2017)

https://further-fc.eu/
Investigation of the Effect of Airborne Contaminants on PEM Fuel Cell Stack Performance and Degradation Using Electrochemical Impedance Spectroscopy, AVL Thda™ and FTIR Gas Analyzer
Authors: Özel Tansu , Bürger Stefan , Cremers Carsten
Published: February 2024

Air pollution is still a bitter truth in many locations in the world. In highly populated regions like metropolitan areas as well as in agricultural areas there are various airborne contaminants which can be harmful to organisms. Also fuel cells, especially PEMFC are sensitive to airborne contaminants.

In most mobile and stationary PEM fuel cell systems, ambient air is used as oxidant gas at the cathode of the fuel cell. It is cost and weight saving because there is no need to install additional tank for pure oxygen and to refill it, but the performance of fuel cell can suffer beyond the oxygen gain from airborne contaminants, which also have the potential to accelerate degradation. To prevent that airborne contaminants reach the fuel cell cathode, air filter systems consisting of particle filter and additional activated carbon filter are installed at the cathode inlet.

The focus here is on the investigation of the use of AVL THDAtm method to detect effects of airborne contaminants. THDA (total harmonic distortion analysis) is a patented online fuel cell monitoring method based on analyzing harmonic distortion effects of voltage drifts instead of single cell voltage measurement. So far it was successfully demonstrated for the detection of water issues like flooding and drying, and for low media supply issues on both cathode and anode side [1, 2].

For the development and validation of the method, experiments with a PEMFC stack are going to be done on a fuel cell testbed equipped with an AVL X-Ion impedance analyzer. Specific air pollutant gases ammonia (NH3), sulfur dioxide (SO2) and nitrogen oxides (NOx) are going to be mixed into the cathode air in the ppb range. Their effects on PEMFC stack performance are going to be investigated with electrochemical impedance spectroscopy (EIS) and total harmonic distortion analysis. The cathode exhaust gas is also going to be analyzed by an FTIR gas analyzer.

It is planned to test the PEMFC stack under different operating conditions, with various parameters and different cathode gas mix ratios while monitoring possible conversion of impurities via FTIR and the stack state of health using THDA and conventional technologies to understand the link between the effect of airborne contaminants on fuel cell stack performance, on its lifetime and to determine possible early indicators in the THDA signals.

References

[1] Mitzel, J., Sanchez‐Monreal, J., Garcia‐Sanchez, D., Gazdzicki, P., Schulze, M., Häußler, F., Hunger, J., Schlumberger, G., Janicka, E., Mielniczek, M., and Gawel, L. 2020. Fault Diagnostics in PEMFC Stacks by Evaluation of Local Performance and Cell Impedance Analysis. Fuel Cells 20, 4, 403–412.

[2] Ramschak, E., Peinecke, V., Prenninger, P., Schaffer, T., and Hacker, V. 2006. Detection of fuel cell critical status by stack voltage analysis. Journal of Power Sources 157, 2, 837–840.
Development of New Electrochemical Method for Measuring Gas Permeability of PEM Fuel Cell Components
Authors: Darabut Alina Madalina , Lobko Yevheniia , Yakovlev Yurii , Matolin Vladimír , Matolínová Iva
Published: February 2024

A Proton Exchange Membrane Fuel Cell (PEMFC) is an electrochemical device that converts directly chemical energy into electrical energy. PEM fuel cells have high efficiency (up to 65%), low working temperatures (between 60‒80 ºC), and produce only water as byproduct [1]. Moreover, these devices are suitable for the replacement of the internal combustion engines with insignificant modifications to the automobile.

The PEMFC consists of a membrane with a catalytic layer, also known as membrane electrode assembling (MEA), gas diffusion layer (GDL), bipolar plates (BPs), and auxiliar components likewise sub-gaskets, and sealings used for preventing the gas leakage [1,2]. An essential material property directly influencing the performance and long-life capacity of the PEM fuel cells is the permeability of their components toward gases (H2 and O2).

Two classical methods can be used for measuring the H2 permeation of the bipolar plates. First one is based on the differential pressure method where the pressurized H2 is passed through the sample and the time rate of decrease/increase of the pressure on the same/opposite side of the sample is measured. The second method is drawn on introducing H2 maintaining the same pressure on both sides, then the transmitted H2 is measured by a chromatography detector [3].

In the present work is proposed a new electrochemical technique for measuring the gas permeability of the BPs. The own-prepared reactor is shown in Fig. 1a. The method is based on covering the sample with a catalytic layer (Fig. 1b) and submerging it in electrolyte. The pressurized H2 is introduced from the bottom of the sample, and the transmitted H2 through it reacts with O2 giving the measured current. Worth noticing that this method is universal and can be used for the analysis of the gas permeation of other semi-conductive and conductive materials not just for FC (e.g., MEAs and GDLs), but other applications.

References:

[1] G. Hoogers, Fuel Cell Technology Handbook, 2003.

[2] Y. Wang, Y. Pang, H. Xu, A. Martinez, K.S. Chen, PEM Fuel cell and electrolysis cell technologies and hydrogen infrastructure development – a review, Energy Environ. Sci. 15 (2022) 2288–2328. https://doi.org/10.1039/d2ee00790h.

[3] R. Blunk, F. Zhong, J. Owens, Automotive composite fuel cell bipolar plates: Hydrogen permeation concerns, J. Power Sources. 159 (2006) 533–542. https://doi.org/10.1016/j.jpowsour.2005.09.068.

Figure 1
In Situ Real-Time Simultaneous NMR Analyses of Anode and Cathode Exhausts of Direct Ethanol and Methanol Fuel Cells
Authors: Hwang Ryeo Yun , Han Oc Hee
Published: February 2024

Understanding the electrochemical reaction mechanisms of energy conversion and storage systems is essential for improving their performance. Nuclear magnetic resonance (NMR) spectroscopy is excellent for probing electrochemical reactions due to its capability to provide quantitative and qualitative information. For the in situ simultaneous acquisition of the anode and cathode exhaust spectra of direct alcohol fuel cells such as a direct methanol fuel cell (DMFC) or direct ethanol fuel cell (DEFC), real-time flow-NMR spectroscopy using a toroid cavity detector was developed in our laboratory. In the cathode exhaust of DMFC, the CD3OH crossed over from the anode as well as HOD was observed. Ex situ NMR spectroscopy cannot detect gas products because they are lost during sample preparation. On the other hand, the amount of CO2 gas detected in the anode exhaust using our in situ detection method was proportional to the HOD amount. It was also proportional to the cell current generated. This explains differences in the fuel cell performance by identifying generated and consumed chemicals and their pathways in the cells at respective conditions. Analyses of DEFC exhausts showed various reaction products such as acetic acid and acetaldehyde but CO2 gas detected was negligible. Our results show that this in situ real-time analysis could identify and quantify the exhaust components, including the gaseous products. Therefore, our results demonstrate that this in situ real-time analysis is appropriate to study the reaction mechanisms of diverse other liquid-flowing electrochemical systems in addition to fuel cells. Furthermore, it may be applicable to designing advanced materials for the systems.
(Digital Presentation) Modeling the Effect of Membrane Electrode Assembly Microstructure on Thermal and Water Transport in Polymer Electrolyte Fuel Cells
Authors: Sánchez-Ramos Arturo , Garcia-Salaberri Pablo A.
Published: February 2024

The effect of water management on oxygen transport plays a critical role in the design of high-performance polymer electrolyte fuel cells (PEFCs) for the automotive industry, especially at low cathode platinum loading [1,2]. In this regard, optimizing the hierarchical pore structure of the membrane electrode assembly (MEA) is crucial to alleviate cathode flooding while ensuring good membrane hydration [3]. However, this task is complicated due to the small dimensions involved in the problem. Mathematical modeling has turned out to be a key tool to understand transport in the thin layered assembly used in PEFCs, including the catalyst layer (CL), microporous layer (MPL) and gas diffusion layer (GDL).

In this work, oxygen, heat and two-phase water transport in the MEA are examined by means of a 1-dimension continuum bundle of capillary tubes model. Experimental pore size distributions (PSDs) are considered for the GDL/MPL/CL assembly. The model takes especial care in analyzing thermal and water behavior in catalyst layer by considering micro (< 20 nm of pore radius), meso (between 20 and 300 nm) and macroscale (> 300 nm) structures as different interconnected domains, each with their own effective thermal conductivity and water saturation. In this aspect, taking into account pore hydrophilicity or hydrophobicity is determinant as water behavior is extremely different.

The model predictions are validated against previous experimental data for various operating conditions and pore structures (Figure 1a). The results offer precise information on the coupling between heat and water transport in both liquid and gas phases, and the impact of operating conditions and transport properties on the saturation distribution through the MEA layers (Figure 1b). Then the continuum bundle of capillary tubes model is also used to run a parametric analysis centered on the obtention of optimal PSD-dependent effective transport properties to produce improved MEA microstructures.

[1] A. Sánchez-Ramos, J.T. Gostick, P.A. García-Salaberri, Modeling the Effect of Low Pt loading Cathode Catalyst Layer in Polymer Electrolyte Fuel Cells: Part I. Model Formulation and Validation, Journal of the Electrochemical Society 168 (2021) 124514.

[2] A. Sánchez-Ramos, J.T. Gostick, P.A. García-Salaberri, Modeling the Effect of Low Pt loading Cathode Catalyst Layer in Polymer Electrolyte Fuel Cells: Part II. Parametric Analysis, Journal of the Electrochemical Society 169 (2022) 074503.

[3] M. Gomaa, A. Sánchez-Ramos, N. Ureña, M.T. Pérez-Prior, B. Levenfeld, P.A. García-Salaberri, M. Rabeh, Characterization and modelling of free volume and ionic conduction in copolymer proton exchange membranes, Polymers 14(9) (2022) 1688.

Figure 1