bluuebunny/crossref_metadata_2025_split huggingface dataset:
Parameterization and Validation of a 2-Dimensional, Transient, Two-Phase MEA Model Capable of Simulating Electrochemical Impedance Spectra
Authors: Eppler Michael , Hanauer Matthias , Gerling Christophe , Berner Ulrich , Eikerling Michael 
Published: February 2024

Proton exchange membrane fuel cells (PEMFC) are promising energy converters, offering both sustainability and efficiency. Achieving optimal performance, however, requires a deep understanding of the underlying cause-effect relationships within the functional layers. One effective approach for validating models that capture the complex physics of PEMFC is through differential cells, which reduce computational effort by allowing along-the-channel-effects to be discarded [1,2].
In this study, we present a 2-dimensional, transient, non-isothermal PEMFC model that enables the disentanglement of loss contributions, facilitating effective material screening. Our model accounts for multiphase transport to provide insights into water management and mass transport. To ensure robust parameterization, we conducted a multitude of both ex-situ and in-situ experiments, reducing our reliance on often-contradictory literature data [3].
We fitted our model to a wide range of polarization curves obtained under operating conditions spanning temperatures of 50-80 °C and relative humidities of 40-100 %. Notably, our model is able to simulate impedance spectra, which enables the disentanglement of processes with different time constants [4]. This approach provides a unique opportunity to study the electrochemical behavior and offers a more profound understanding of PEMFC performance limitations. The thorough parameterization process and validation against a broad range of operating conditions and impedance spectra render our model reliable and effective for industry professionals and researchers. We also highlight shortcomings and physics aspects that require further research to deepen insights and enable faster industrialization cycles.

References

[1] Gerling, C., Hanauer, M., Berner, U., & Friedrich, K. A. (2022). PEM single cells under differential conditions: full factorial parameterization of the ORR and HOR kinetics and loss analysis. Journal of The Electrochemical Society, 169(1), 014503.
[2] Pant, L. M., Stewart, S., Craig, N., & Weber, A. Z. (2021). Critical Parameter Identification of Fuel-Cell Models Using Sensitivity Analysis. Journal of the Electrochemical Society, 168(7), 074501.
[3] Vetter, R., & Schumacher, J. O. (2019). Experimental parameter uncertainty in proton exchange membrane fuel cell modeling. Part I: Scatter in material parameterization. Journal of Power Sources, 438, 227018.
[4] Gerling, C., Hanauer, M., Berner, U., & Friedrich, K. A. (2023). Experimental and Numerical Investigation of the Low-Frequency Inductive Features in Differential PEMFCs: Ionomer Humidification and Platinum Oxide Effects. Journal of The Electrochemical Society.

Figure 1
Investigating the Applicability of Rotating Disk Electrode Measurements for Determining Catalyst Activity in Fuel Cells
Authors: Müller Marcel , Melke Julia , Kintzel Birgit 
Published: February 2024

Currently, the mass production of fuel cells is mainly limited by the availability and the price of platinum, which is typically used as the catalyst for the hydrogen oxidation reaction (HOR) as well as for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFC). To eliminate or at least reduce this limitation, it is necessary to develop new catalytic systems, which are based on other, cheaper active components or at least require less platinum. For the characterisation of catalysts, many different methods are in use for the physical and the chemical part. For example, the rotating disk electrode (RDE) is a widely used method for characterizing catalysts in electrochemistry. However, RDE measurement does not reflect the same reaction conditions as exist in a fuel cell. Nevertheless, characterisation by RDE tests is often used for pre-selection at an early stage of catalyst development. In later stages of development, catalyst investigations are carried out by full-cell or half-cell tests.
In this work, we will compare the oxygen reduction reaction (ORR) properties of Pt/C catalysts from RDE measurements with those from CCM measurements in half-cell and full-cell configurations to determine what correlations can be made between the different type of investigations.
Neutron Nanomediators for Non-Invasive Temperature Mapping of Fuel Cells
Authors: Ruffo Antonia , Strobl Markus , Kenzelmann Michel , Boillat Pierre 
Published: February 2024

Polymer electrolyte fuel cells (PEFCs) have gained significant attention in the past century for their ability to convert hydrogen chemical energy into electrical energy. However, the technology still requires refinement due to losses in polarization, ohmic resistance, and mass transport that result in heat generation, negatively affecting the device water management and durability. To better understand these processes, researchers initiate studies to improve knowledge of the temperature at the cell structure core. However, current methods using micro-thermocouples [1] are highly invasive, impeding cell operation and limiting data accuracy.
The project aims to overcome the latter problem using ferromagnetic nanoparticles for non-invasive temperature mapping on these devices. A key part of this novel method is the application of Neutron Imaging through a polarized beam [2], which allows to detection of the temperature distribution on the surrounding nanosensors. The dispersed ferromagnetic nanomediators, in these conditions, depolarize the incoming neutron beam due to the random magnetic field produced by the nanoparticles themselves. Furthermore, as the temperature rises toward the Curie temperature (Tc), the nanosensors tend to lose their magnetic preferential orientation, influencing the neutron beam polarization gradually less as the ambient temperature increases.
This project includes identifying a suitable material, synthesizing nanoparticles through solution techniques [3], and performing physical and magnetic ex-situ characterizations. By dispersing them in Polytetrafluoroethylene micro-powders, nickel, iron, and Nd2Fe14B alloys were initially studied at different concentrations, grain sizes, and magnetic environments, showing promising signal detection (η) and absolute thermal variation (Δη) results.
References
[1] S.-K. Lee, et al., Electrochemical and Solid-State Letters, 12, B126 (2009).
[2] M. Strobl, et al., Journal of Physics D: Applied Physics, 52, 123001 (2019).
[3] Couto GG, et al. Journal of Colloid and Interface Science. 311 (2007)

Figure 1
Electrospun Fuel Cell Electrodes and Their Behavior Under Hydrogen/Air Start-up/Shut-Down Conditions
Authors: Kallina Valentina , Oezaslan Mehtap , Hasche Frederic 
Published: February 2024

Affordable and clean energy is one of the 17 sustainable development goals proposed by the United Nations in 2015. [1] In this context, polymer electrolyte membrane fuel cells (PEMFCs) are a promising renewable and clean energy conversion technology. The large implementation of PEMFCs, however, is hindered by high loading of very costly and scarce platinum group metals (PGM) and insufficient long-term durability. Most of the cathode catalysts are suffering from hydrogen/air start-up/shut-down (SUSD) conditions. [2, 3] Generally, the performance of the PEMFC is controlled by the utilization of the catalytically active sites and the mass transport properties within the porous catalyst layers (CL) in particular operating at high current density. New strategies in the design of functional porous catalyst layers are needed to overcome these challenges. As a very promising strategy, nanometer-sized fibers prepared by electrospinning can be used as a backbone to improve the utilization and accessibility of catalytically active sites by maintaining the PGM loading. [4, 5]
In this work, a nozzle-free electrospinning machine by Elmarco S.R.O. (Liberec, Czech Republic) was employed to design and nano-engineer advanced catalyst layers with improved catalytic as well as mass transport properties. Thereby, several highly homogeneous catalyst layers deposited on gas diffusion layer with controlled platinum loading of up to 0.1 mg/cm2 were prepared and characterized by scanning electron microscope (SEM) and micro X-ray fluorescence spectroscopy (μ-XRF). The structural information such as morphology and chemical distribution was correlated with the electrochemical data obtained from the single cell measurements in a fuel cell test station. Additionally, the durability of the as-prepared nanofiber-based catalyst layers was studied under real hydrogen/air SUSD conditions.
Our results show the impact of different nanostructured catalyst layers prepared by electrospinning process on the long-term performance of the PEMFC. Here, we will present the great advantages of the electrospun catalyst layers over the classical catalyst layers prepared by decal transfer process.

References

[1] https://sdgs.un.org/goals/goal7 (date 26 March 2023).
[2] Mittermeier et al., J. Electrochem. Soc. 2017, 164 (2) F127-F137. DOI: https://doi.org/10.1149/2.1061702jes
[3] Mittermeier et al., J. Electrochem. Soc. 2018, 165 (16) F1349-F1357. DOI: https://doi.org/10.1149/2.0931816jes
[4] M. Brodt et al., J. Electrochem. Soc. 2013, 160 (8), F744-F749. DOI: https://doi.org/10.1149/2.008308jes
[5] W. Zhang et al., ChemSusChem 2011, 4 (12), 1753-1757. DOI: https://doi.org/10.1002/cssc.201100245
Enhanced Water Management in Fuel Cell Cathodes by the Application of Superhydrophobic Fluorinated Carbon Microporous Layers
Authors: Lyth Stephen Matthew , CAN Enes Muhammet , Sasaki Kazunari 
Published: February 2024

Under high current density operation, the efficiency of polymer electrolyte fuel cells (PEFCs) can dramatically decrease. This is due to water accumulation at the cathode side, preventing oxygen diffusion to the electrocatalyst. As such, effective water management is of vital importance by use of a suitable gas diffusion layer (GDL) and/or microporous layer (MPL). MPLs generally consist of carbon black as the porous electron conducting phase, and polytetrafluoroethylene (PTFE) as a hydrophobic binder. Here, we instead use superhydrophobic fluorinated carbon powder in the MPL as a novel material to decrease the required PTFE content. It is confirmed that the water contact angle of the MPL can be increased from 131° to 151° by using fluorinated carbon. Moreover, the fluorinated carbon MPL shows lower oxygen transport resistance at high humidity. Furthermore, in single fuel cell tests at various temperatures and relative humidity values, the I–V performance is significantly and consistently better than for the conventional MPL. These results confirm that fluorinated carbon is a promising new material for water management in the MPLs of PEFCs.
This paper is based on results obtained from project JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).
1. Tailored Wettability in Fluorinated Carbon Nanoparticles Synthesized from Fluorotelomer Alcohols, E. Can, M. Nishihara, K. Sasaki, S. M. Lyth, Applied Surface Science, 157136 (2023)
2. Superhydrophobic Fluorinated Carbon Powders for Prevention of Flooding in PEFCs, E. M. Can, A. Mufundirwa, T. Kitahara, M. Nishihara, K. Sasaki, S. M. Lyth, Journal of Power Sources, 548, 232098 (2022)
3. Solvothermal Synthesis of Superhydrophobic Hollow Carbon Nanoparticles from Fluorinated Alcohol, S. M. Lyth, W. Ma, J. Liu, T. Daio, K. Sasaki, A. Takahara, and B. Ameduri, Nanoscale, 7, 16087 (2015)
Effects of Operating Conditions on Membrane Electrode Assembly Saturation and Hydration Revealed By Operando Small- & Wide-Angle X-Ray Scattering
Authors: Aliyah Kinanti Hantiyana , Lazaridis Timon , Berger Anne , Appel Christian , Sicairos Manuel Guizar , Menzel Andreas , Gasteiger Hubert Andreas , Buechi Felix N. , Gubler Lorenz , Eller Jens 
Published: February 2024

Operando scanning small- and wide-angle X-ray scattering (SAXS&WAXS) at the cSAXS beamline of the Swiss Light Source was employed in this study to examine the water saturation of polymer electrolyte fuel cell (PEFC) component, particularly in the nanoscale pore space of catalyst layers (CL) and the membrane hydration state. A small beam size (≈7x30 microns) and ≈0.6 microns through-plane step size enabled to resolve of the bulk CLs (Pt/C Ketjen Black based, 0.1 mgPt/cm2; ≈7 microns thick) separated by a 15-micron membrane. Additionally, it allows for precise registration in case of membrane swelling during operation, which is a prerequisite for the analysis of the operando scattering data. Due to the difference in electron density variation between solid-void and solid-liquid interfaces, any change in CL saturation results in different scattering intensity profiles, which can be quantified by Invariant calculations (see Fig. 1a & b).
The presentation will give insights into CL saturation evolution concerning relative humidity, operating pressure and current density. Differences in the CL saturation, and membrane hydration indicated by a change in d-spacing of the ionomer peak (1), were observed between wet nitrogen flushing and cell operation (see Fig. 1c & d). However, the cathode microporous layer (MPL) saturation seems to be unaffected for a Li100-based MPL on a Freudenberg H14 gas diffusion layer (GDL) substrate. The length scale-specific scattering data will provide a better understanding of mass transport in PEFC’s materials and allow us to push material design development forward. We acknowledge the Paul Scherrer Institut, Villigen, Switzerland for provision of synchrotron radiation beamtime at beamline cSAXS of the Swiss Light Source.

References:

S. W. Shi, A. Z. Weber and A. Kusoglu, J Membrane Sci, 516, 123 (2016).

Figure 1
Study of Fuel Cell Stacks Combining Pseudo-3D Multi-Physics Simulations with Experimental Mappings of Current Density and Liquid Water
Authors: Poirot-Crouvezier Jean-Philippe , Morin Arnaud , Balestriere Pierrick , Vacquier Christophe 
Published: February 2024

In this work, experimental and numerical analyses of Proton Exchange Membrane Fuel Cell stacks for automotive application are proposed. Performance and durability of PEMFC stacks strongly rely on an optimized water management. An adequate balance has to be found between a sufficient membrane hydration enhancing electrical conductivity and a limited liquid water presence avoiding water flooding. This requires investigations at a local scale inside the cells, because the location of water condensation is not distributed homogeneously in the active area, due to spatial variations of temperature, gas composition or current density.
Allowing the quantification of liquid water locally inside PEMFCs, neutron imaging is a powerful tool for the analysis of fuel cell operation at a local scale. It is generally used with single cells and not with stacks, due to the complexity of such experiments. A quantification of liquid water over the active area is obtained through neutron imaging of stacks for several operating conditions. Specific segmented high surface sensors are placed inside stacks to map the current density and temperature distribution in the same area. A multi-physics pseudo-3D two-phase flow model coupling all the electrochemical and transport phenomena supports the understanding of the relationship between all these parameters. The comparison with experimental mappings validates the model, which is able to predict both the current density and the amount of liquid water at a local scale. Unlike experimental measurements that gives a total amount of liquid water in the cell, the model allows to distinguish between anode and cathode sides, or between channels and GDLs, providing crucial information regarding flooding phenomena. Moreover, the flowing direction of the fluids inside the stack have a major influence on liquid water distribution. As a general trend, it is observed that the average total water thickness always decreases when current density increases, in all tested stack flow configurations. Furthermore, a clear relationship appears between flooding, cathode pressure drop and cathode liquid water content. Finally, a detailed analysis is proposed to explain the flooding phenomena, in order to improve the fuel cell stack control.

Figure 1
(Invited) Beyond Electrochemical Impedance Spectroscopy: Advanced Methods for Studying the Dynamics of Electrochemical Processes
Authors: Vidakovic-Koch Tanja 
Published: February 2024

The most popular technique for characterizing various electrochemical devices such as fuel cells, water electrolysis or batteries is electrochemical impedance spectroscopy (EIS). However, due to the coupling of dynamic phenomena with similar time constants, EIS often fails to separate the contributions of individual processes to overall performance losses. In this case, obtaining useful information from the EIS spectra can be
be difficult and the interpretation of the observed patterns is unclear. In this talk, I show that new dynamical methods based on the use of nonlinearities in the system response (nonlinear frequency response analysis (NFRA) [1]), non-electrical inputs (concentration-alternating frequency response analysis (cFRA) [2]), or data-driven analyses (Loewner framework [3]) can provide additional information for understanding electrochemical conversion processes. Our current examples are related to the study of polymer electrolyte membrane electrolysis and polymer electrolyte membrane fuel cell.
References
[1] Vidaković-Koch T., Miličić, T., Živković, L.A., Chan, H.S., Krewer, U., Petkovska, M., (2021) Nonlinear Frequency Response Analysis: A Recent Review and Perspectives, Current Opinion in Electrochemistry, 100851.
[2] Sorrentino, A., Sundmacher, K. & Vidaković-Koch, T. (2020). Polymer Electrolyte Fuel Cell Degradation Mechanisms and Their Diagnosis by Frequency Response Analysis Methods: A Review. Energies, 13(21), 5825.
[3] Antoulas, A. C., Lefteriu, S., and Ionita, A. C., (2017) A tutorial introduction to the Loewner framework for model reduction in Model Reduction and Approximation, Eds: P. Benner, A Cohen, M. Ohlberger, K. Willcox, Siam Comupational Science and Engineering, Chapter 8, pp. 335–376.
Noninvasive Local Impedance Determination in Polymer Electrolyte Fuel Cells Stacks
Authors: Schuller Arnaud , Schmidt Thomas J. , Eller Jens 
Published: February 2024

Water management in polymer electrolyte fuel cells (PEFC) needs to ensure a homogeneous membrane humidification without local dryout or flooding from inlet to outlet of cell with active areas of some hundreds of square centimeters. Measurement methods that are able to provide spatial resolved information on the current density, membrane conductivity or water content distributions of PEFCs are usually invasive and therefore difficult to use in actual applications. Based on the learnings of the development of electrical impedance tomography (EIT) for PEFCs [1], a new method is presented that is capable to determine 1D humidity profiles between the gas inlet and outlet in a 6-cell commercial stack [2,3]. Local AC current injections and voltage measurements are performed using electrodes positioned all around the fuel cell attached to the flow field plates (see Figure 1a). Each electrode combination characterizes a specific area of the cell as the current crosses the membrane electrode assembly (MEA) very locally.
The presentation will discuss the calibration of the local impedance values, the sensitivity of the approach to relative humidity (rH) gradients in the cell (see Figure 1b) and present use cases of measurements during fuel cell operation. Finally, we will present results on multiply frequency AC stimulation that allows local electrochemical impedance measurements and thereby insights beyond membrane conductivity, i.e. into mass transport limitations due to water accumulations in the cell.
References
[1] A.Schuller, et al., J. Electrochem. Soc. 2022, 169, 044525. DOI: 10.1149/1945-7111/ac6390
[2] A.Schuller, et al., J. Electrochem. Soc. 2022, 169, 074504. DOI: 10.1149/1945-7111/ac7a62
[3] A.Schuller, et al., J. Electrochem. Soc. 2022, 169, 124512. DOI: 10.1149/1945-7111/aca03a
Figure 1: a) Scheme of simplified PEFC geometry with electrodes locations at the flow field’s outer surface that are used for current injection (black arrows) and potential measurements (gray arrows) in varying combinations during data acquisition; b) Determined distribution of the cells high frequency resistance for different stack operating conditions (temperature 70°C, RH inlet & outlet 50%).

Figure 1
Spatial Atomic Layer Deposition of Iridium Oxide Electrocatalyst Layers for PEM Electrolysis
Authors: Frijters Corné , Jain Hardik , Shen Jie , Ameen Mahmoud , Greer Jamie , Blasco Nicolas , Poodt Paul 
Published: February 2024

Proton Exchange Membrane Water Electrolysis (PEMWE) is a commonly used technique to produce green hydrogen from water. A massive upscaling of PEMWE installations is required in the coming decade to keep up with the foreseen demand for green hydrogen. State-of-the-art PEM electrolyzers make use of iridium-based electrocatalyst layers with iridium loadings of 1-2 mg/cm2. The high cost and limited availability of iridium will limit the scalability of PEMWE if the iridium loading cannot be reduced.
Atomic Layer Deposition can be used to apply thin and highly conformal IrO2 films on porous substrates with atomic-scale control of the amount of material that is deposited. When applied to PEM electrolyzers, this can be used to significantly reduce the loading of IrO2. Recently, IrO2 catalyst layers for PEM electrolyzers applied by Spatial ALD with iridium loadings well below 0.1 mg/cm2 have been reported [1]
We will present plasma enhanced Spatial ALD of iridium oxide and metallic iridium films using a new iridium precursor developed by Air Liquide Advanced Materials. The electrocatalytic efficiency and stability has been characterized using RDE, showing that IrO2 films of just a few nanometer demonstrate an excellent catalytic activity and stability. IrO2 films have been conformally deposited on high surface area titanium porous transport layers (PTL’s) as well as Nafion membranes. First demonstrations on full PEM stack scale show that Spatial ALD can enable iridium loads 10-100x lower than the state of the art while demonstrating an excellent stability in accelerated stress tests.
We will also discuss how Spatial ALD of IrO2 films can be up-scaled to mass production, with emphasis on efficiency or precursor utilization and precursor recovery for recycling.
[1]: https://www.tno.nl/en/newsroom/2022/10/breakthrough-electrolyser-development/