bluuebunny/crossref_metadata_2025 huggingface dataset:
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)
Demonstration of Fast Simultaneous Neutron and X-Ray Tomography for Fuel Cell Water Content Measurements
Authors: LaManna Jacob Michael , Daugherty Michael Cyrus , Kim Youngju , Hussey Daniel Seth , Baltic Eli , Jacobson David
Published: February 2024

Neutron radiography has been a powerful tool for measuring water content within operating fuel cells. The resolution for neutron imaging has been steadily improving and has demonstrated the ability to measure water content in industrially relevant catalyst layers. The difficulty in measuring catalyst layer or interfacial water content with neutron radiography is that the method assumes that the layers of the MEA are flat and uniform with no variation which is a poor assumption. To combat this assumption, it is necessary to move to neutron tomography that resolves the fuel cell in three dimensions. Combining neutron tomography with simultaneous X-ray tomography improves layer and interface identification which facilitates better water saturation measurements. In addition to capturing the “waviness” of the MEA, this method can be applied to tracking water distribution in structured 3D electrodes. This talk will demonstrate current developments in fast simultaneous neutron and X-ray tomography, methods to improve saturation calculations within the various porous layers, and showcase new hardware developments available to the NIST user community.
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
Characterization of Transport Pathways in Electrolyzers Using Neutron and X-Ray Tomography
Authors: Daugherty Michael Cyrus , LaManna Jacob Michael , Kim Youngju , Hussey Daniel Seth , Baltic Eli , Jacobson David
Published: February 2024

Electrolysis is a critical component to realizing a true green hydrogen economy. The performance and efficiency of an electrolyzer is directly tied to the multiphase transport that occurs within the porous transport layer (PTL). The PTLs must allow sufficient water transport to the catalyst layer to maintain the reaction while removing the product gases. PTLs are typically created from titanium foams or sintered from titanium powders or fibers. The resultant structure is heterogenous and requires 3D imaging to properly capture the pore structure and transport pathways. The use of titanium for the PTL can make it difficult to track the multiphase flow using X-rays alone as the X-ray energy required to penetrate 1 cm or more reduces the contrast between water and oxygen without the use of contrast agents that could affect the reaction. Neutrons provide a penetrating probe capable of imaging through titanium while having extreme sensitivity to water. Combing neutrons and high energy X-rays provides an easy way to identify all components in the PTL, i.e., the solid structure, oxygen, and water. The National Institute of Standards and Technology provides the Neutron Imaging Facility to the larger research community through the Center for Neutron Research facility user program. This instrument provides the ability to perform simultaneous neutron and X-ray tomography. Moving from 2D radiography to 3D tomography is critical to fully understand the influence of the PTL pore structure on the multiphase transport. This talk will give an overview of the instrument capabilities, showcase past success for neutron imaging of electrolyzers, and provide current progress on development of hardware and data reduction methods for simultaneous neutron and X-ray tomography of electrolyzers.
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/
Highly Robust Fuel Cell Electrodes Using Pt Thin Film Catalysts As Reversal Tolerant Anodes
Authors: Liyanage Wipula Priya Rasika , Komini Babu Siddharth , Ince Alper Can , Pasaogullari Ugur , Spendelow Jacob S.
Published: February 2024

Recent years have seen a rise in interest in polymer electrolyte membrane fuel cells (PEMFCs) because of its high power density, high energy efficiency, and zero-emission characteristics. PEMFC-powered fuel cell electric vehicles (FCEVs) have the potential to significantly lower the transportation sector's carbon dioxide emissions, paving the way for the global adoption of the hydrogen economy. However, the durability and robustness of fuel cell systems must be increased before a wider commercialization of FCEVs is possible. The hydrogen starvation in anode, occurring during start-up/shutdown or cold start, can cause rapid and significant deterioration of the performance and durability of a PEMFC system through cell reversal. In hydrogen-starved conditions, the cell's performance can deteriorate in just a few minutes, leading to sudden cell failure. Prior studies have been conducted to understand the degradation caused by hydrogen starvation and cell reversal in PEMFCs, with the aim of identifying mitigation solutions that could minimize deterioration of membrane electrode assembly (MEA) components. In this work, we present a novel materials strategy to mitigate cell damage using a thin film Pt anode catalyst supported on Nafion nanowires in a co-axial configuration. Due to the high roughness of Nafion nanowire, the coaxial nanowire electrode (CANE) negates the needs for conventional carbon support and displays exceptional robustness to reversal tolerance. This work will present a systematic evaluation of CANE as reversal tolerant anodes compared to conventional supported catalyst (Pt/C). Further enhancement in durability by integration of iridium with CANE anode will also be presented.

Acknowledgement

This research 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. Authors would also like to acknowledge support for this work from the Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory (LANL) (2020200DR).
Modeling and Sizing of a Y-Shaped Laminar Flow Micro-Fluidic Fuel Cell
Authors: Espinoza Andaluz Mayken , Zhang Xiaoqiang , Yang Danan , Andersson Martin
Published: February 2024

The high demand for portable and desktop electronic devices requires mobile energy sources. Electronic devices, in general, are small when they are portable and require autonomy, sustainability, efficiency, and large enough periods of operability. In that sense, microtechnology, a type of technology related to the manufacture of prototypes or three-dimensional high-precision products in various materials ranging in size from tenths of microns to a few millimeters, has reached a boom in microfabrication of devices that are not exclusively electronic. Applications in several fields show that micro-energy sources are a focal point for commercializing prototypes in the mobility sector.

The energy demand to supply micro-devices has been increasing in recent years. Considering the power output of the laminar flow microfluidic fuel cell (LFFC), it is a suitable solution to provide the required electrical energy in small devices. The absence of electrolytes and no requirement of platinum as catalytic material are two of the most important advantages of this type of fuel cell. The current study provides detailed information about the design and characteristics of an LFFC. A complete analysis of the different channel shapes is considered in this study, with the Y-shaped channel being selected as the best option. The impact of the inclination degree for the inlet channels has been considered to evaluate the average velocity the flow acquires in the channel. In addition, the voltage-current behavior considering the materials, fuel/oxidant, and design characteristics has been obtained through modeling approaches.

Figure 1. Velocity profile and Reynolds number in the mid-plane of the Y-channel design

Figure 1
Projected Fuel Cell Stack Costs Using Non-PGM Cathode Electrocatalysts
Authors: Swider-Lyons Karen , Patel Sejal , Rainford Chris
Published: February 2024

Platinum is typically used at the cathode of the cathode of proton exchange membrane fuel cells (PEMFCs) to overcome the kinetic limitations of the oxygen reduction reaction (ORR) to water. Pt is a noble metal that is mined mainly in South Africa and Russia. At present costs of $965 per troy ounce ($31 per gram), the cost of Pt in the cathode is approximately 40% of the total cost of each PEMFC membrane electrode assembly (1,2). Supply chain concerns have been raised that there is insufficient Pt in the world to support the conversion of all automobiles to hydrogen, or that increasing the demand of Pt through mass commercialization of fuel cells would drive up its demand and then cost (1,3). Researchers have therefore looked for catalysts that do not contain Pt or other precious metals (3). Oxygen reduction without Pt is possible, and all living creatures and plants use cytochrome enzymes with reactive iron or copper sites as part of a catalytic cycle to reduce O2 to reactive oxygen. Significant improvements have been gained in the performance of fuel cells with non-PGM cathodes by improving the density of sites and improving the catalyst durability (4).

We estimate the cost impact of eliminating Pt from the cathode of a heavy-duty fuel cell stack. The calculations are based on the comparison of Plug fuel cells with Pt cathodes, compared to literature polarization curves for cells and stacks containing PGM-free cathodes (note that the anodes still contain Pt). We carry out a sensitivity analysis using different costs to the non-PGM catalysts. Our primary finding is that eliminating Pt from the cathode does little to reduce stack costs because the performance of the fuel cells with non-PGM cathodes is low, and larger stacks are needed to meet performance requirements. We will also discuss how using a non-PGM cathode affects projected recycling costs.

References:

[1]. A. Kongkanand, M. F. Mathias, J. Phys. Chem. Lett. 2016, 7, 1127−1137

[2]. B.D. James, J. Huya-Kouadio, C. Houchins, D. Desantis, Strategic Analysis, Inc. Technical Report. DOI: 10.13140/RG.2.2.36532.55683.

[3]. C. Sealy, Materials Today, 2008, 11, 65.

[4]. F. Jaouen, E. Proietti, M. Lefevre, R. Chenitz, J.-P. Dodelet, G. Wu, H. T. Chung, C. M. Johnston, P. Zelenay, Energy Environ. Sci., 2011, 4, 114.
Anode Defects’ Propagation in Polymer Electrolyte Membrane Fuel Cells Stack
Authors: Bultel Yann , BAS Corine , Dubelley Florence , Micoud Fabrice , Rosini Sébastien , Nayoze-Coynel Christine
Published: February 2024

Reliability and durability are key considerations to successfully deploy Proton Exchange Membrane Fuel Cells (PEMFCs). Defects induced by manufacturing processes and fuel cell operating conditions may shorten the lifetime of PEMFC due to membrane electrode assembly (MEA) components degradations. If the degradation mechanisms occurring along ageing are now well-known, the propagation of these defects to other materials or to other locations in the stack was poorly investigated in the literature. Recently, we investigated a defect-propagation in MEA via accelerated stress tests combining load and load-driven humidity cycling, and open-circuit voltage. Results highlighted a defect propagation in term of anode and cathode ECSA losses. Significant membrane thinning is also observed for the defective segments. If, the defect propagation was investigated at the cell scale, it has been barely studied in the literature at the stack level.

The objective of this work is to quantify the impact of MEA manufacturing defects on the performance and durability in stack and to analyze how these defects can propagate within healthy areas of the same MEA or to healthies MEAs within a stack.

Tests were carried out on two stacks with metallic bipolar plates. The stacks were assembled using 35 defect-free MEAs for the healthy stack and using 30 homogeneous MEAs and 5 MEAs with controlled anode defects over 25% of the active area (absence of anode catalyst layer) for the faulty one. The two stacks were operated on a test bench able to control operating conditions and electrochemical characterizations were regularly made in order to evaluate the impact of the defects on the stack behavior.

The initial characterization of the stack contained faulty MEAs showed, as expected, that the defects in the anode active layers have a significant effect on the performance of the cells from the conditioning stage. The analysis of the degradation rate showed that the cells directly in contact with the defected MEAs were the ones whose performance degraded the fastest, which implies that the presence of defects within the stack induces a propagation of the performance decrease. This phenomenon could be linked to a significant increase in hydrogen leakage through the membrane identified both by off-line electrochemical characterization and by thermal camera measurements in post-mortem analysis. The mechanism of degradation is still difficult to understand but the presence of defects within the stack could lead to constriction of the current lines around the defect and to localized heating which could degrade the membrane relatively rapidly.

Figure 1
Investigation of Ionomer/Catalyst Interfacial Degradation in PEMFC Using Pt Nanoparticle Array Electrode
Authors: Lee Dong Wook , Hyun Jonghyun , Seok Kyunghwa , Oh Euntaek , Bae Hanmin , Park Jeesoo , Kim Hee-Tak
Published: February 2024

Interface between catalyst and ionomer in the catalyst layer of polymer electrolyte membrane fuel cells (PEMFCs) has been a subject of keen interest, but its effect to the durability has not been fully understood due to the complexity of catalyst layer structure. Herein, we suggest Pt nanoparticle (NP) array electrode fabricated using block copolymers as a platform for a focused investigation of Nafion/Pt interface. The interfacial evolution between Pt NP and Nafion thin layer during holding with various fixed potentials were investigated using the Nafion thin layer-coated Pt NP array electrode. A set of analysis for the electrodes with various fixed potentials reveals that the Nafion thin layer becomes densely packed and the interaction between the end group of Nafion side chain and Pt surface is facilitated at the intermediate operating potential (0.4~0.7 V). The rearrangement leads to an increase of oxygen transport resistance, negatively impacting the power performance of PEMFC. The Pt NP array electrode provides a versatile tool to analyze Nafion/Pt interface and fresh insight on the degradation mechanism of PEMFC.
(Invited) Addressing Durability in Long-Life, Low-Power Fuel Cells
Authors: Leonard Daniel , Borup Rod L. , Rockward Tommy , Kreller Cortney R. , Wilson Mahlon , Siller Victor , Usov Igor
Published: February 2024

Fuel Cells’ scalability and energy density make them excellent candidates for different applications, especially difficult to electrify applications. Their design flexibility can also be applied to low power, long-life applications. LANL has constructed a unique design to provide continuous, low power (< 100 µW) for very long duration (multiple decades). This LANL system operates passively, without active control of cell parameters, such as temperature and humidity. In addition, the system does not require interventions like refueling or maintenance during its operational lifetime. While the application and operational conditions of the systems mentioned here differ greatly from those of light and heavy-duty vehicles (e.g. ambient temperature operation, passive water management, low current densities), many of the modes of degradation are similar, and listed below:

Membrane thinning

Degraded performance due to loss of electrochemical surface area (ECSA)

Loss of water management due to changes in hydrophobicity

Increased cell resistance due to corrosion of cell components

To better understand these degradation processes LANL has performed accelerated stress tests (ASTs) to induce and quantify the membrane thinning, loss of ECSA, hydrophobicity, and bipolar plate corrosion. Those ASTs include long term OCV holds with reactants present, high potential cycling (1-1.5 V) in flooded conditions, potential cycling to induce catalyst Ostwald ripening, and exposure of cell components to corrosive environments.
Supercapacitive Electrolyzer for Decoupled Hydrogen Production
Authors: Toledo Carillo Esteban , García-Rodríguez Mario , Sanchez-Moreno Lorena , Dutta Joydeep
Published: February 2024

The production of green hydrogen is an energy vector and key component to tackle the decarbonization goals. Electrolysis of water for production of green hydrogen using renewable energy sources is an attractive approach, but the integration of electrolysis technologies with these sources is still facing challenges such as membrane degradation and gas crossover. Decoupled electrolysis is a promising approach to overcome these challenges. In this approach, the generation of hydrogen and oxygen can be separated in time or space, which allows for efficient and reliable integration with renewable energy sources. Symes et.al. developed a two-step electrochemical system that separates the water oxidation and hydrogen evolution reactions using an electron-coupled proton buffer. However, most decoupling designs still require the use of membranes for separation of redox mediator, which can be susceptible to degradation and have limited lifetimes. Researchers have introduced solid-state mediators to build membraneless electrolyzers using battery-like materials. The use of solid-state mediators eliminates the need for membranes and can provide improved performance and stability.

In this work, we introduce a membraneless architecture decoupled hydrogen production in a hybrid cell combining the standard electrocatalytic reactions of water splitting with a capacitive storage mechanism. This innovative approach increases the flexibility and robustness of the hydrogen production system, allowing for operation in both acidic and alkaline conditions. The supercapacitive electrolyzer was assembled using the bifunctional catalyst cobalt-iron phosphide prepared by electrodeposition and a commercial activated carbon cloth as a capacitive electrode. The results of this work demonstrate the potential of membraneless electrolysis for green hydrogen production. The hybrid cell achieved an energy consumption of 48 kWh/kg at a nominal current density of 10 mA/cm2 in a 5 x 5 cm2 cell. Faradaic efficiencies over 99% were achieved at 100 mA/cm2. The cycle stability of the single cell was demonstrated over 20 h of operation (100 cycles) at a current density of 20 mA/cm2 with no apparent electrode degradation. Moreover, the simplicity of the cell design in this study not only facilitates quick scaling of production but also offers significant advantages in terms of operational cost and maintenance, as membraneless electrolyzers eliminate the need for expensive and complex components. To further enhance the performance of the hybrid cell for green hydrogen production, it is possible to reduce the ohmic contribution of the capacitive electrode and lower the overpotential required for the bifunctional catalyst to facilitate efficient water splitting.
Hydrogen Fuel Cell Aiming at Vehicle Propulsion: Onboard or Off-Board Electricity Generation?
Authors: Santos Andrade Tatiana , Thiringer Torbjörn
Published: February 2024

In response to the global energy crisis and climate change, hydrogen has been pointed out as promising fuel to be part of the green energy transition. Thus, countries worldwide have released policies to support and increase the hydrogen industry. Therefore, investigations regarding how hydrogen can be utilized best as a fuel should be addressed to evaluate its potential applications. Since transportation is responsible for 37% of the carbon emissions from the end-use sectors, it is of interest to consider hydrogen fuel for vehicle propulsion. There are two main alternatives that might be considered for the electricity generation from hydrogen: 1) a hydrogen fuel cell onboard the electric vehicle or 2) a hydrogen fuel cell off-board powering the electric vehicle.

Therefore, in this work, we propose the modeling and simulation from hydrogen fuel to wheels of the two different systems using the WLTP as the driving cycle reference. For the onboard system, the following components were considered: the vehicle dynamics, the gear, the motor, the inverter, the battery, and the fuel cell system on board (fuel cell vehicle powertrain). For the off-board system, the following components were considered: the vehicle dynamics, the gear, the motor, and the inverter for the battery electric vehicle powertrain, followed by the charger, the grid, and the fuel cell system off-board. The components were modeled as further described.

The vehicle dynamics were modeled mathematically and the weight difference between the vehicles was taken into account. The gear was a single-step gear. The motor was an eight-pole PMSM and the inverter three-phase IGBT. The battery for both was modeled as a lithium-ion battery with different sizes, with the battery for the fuel cell vehicle being much smaller. Capacity values similar to commercialized vehicles were used (4 and 300 Ah). The fuel cell was modeled as a commercialized fuel cell with 63% peak efficiency. For the fuel cell vehicle, a control strategy was implemented to split the power demand between the fuel cell and the battery. The control strategy was based on the state of charge of the battery and the power demand for each point of the cycle.

The simulation results have shown a slightly higher efficiency and lower hydrogen consumption for the onboard system compared to the off-board system. Even though there were more losses associated with the battery and the fuel cell in the onboard system, the losses associated with vehicle weight and the off-board power electronics related to the off-board system were more significant to the overall energy consumption. Thus, the results suggest that if hydrogen is available as a fuel aimed at vehicle propulsion using it onboard is more efficient than using it off-board.
Miniature Fuel Cell with Monolithically Fabricated Si Electrodes- Application of a PDMS Flow Channel for Operando Observation -
Authors: Hayase Masanori , Yoshimura Gaku , Sakai Yuta , Yamaguchi Takeo
Published: February 2024

Miniature fuel cells have attracted attention as an ultimate portable power source, and we have developed monolithically fabricated Si electrodes for the miniature fuel cells [1,2]. In the fuel cells, two Si electrodes with porous Pt catalyst layer are pressed onto either side of a PEM (polymer electrolyte membrane) , and the prototype fuel cells showed promising performances of over 500mW/cm2 output at 313K with H2-O2. However, the high output was obtained with only small reaction area. Along with enhancement of the reaction area, the performance dropped. We assumed that the performance drop is caused by flooding due to increased water production, which was ignored because MEMS fuel cells are dimensionally small and the outputs are also small. In this study, we attempted to observe the behavior of produced water on the fuel flow channel using a novel transparent channel cover as shown in figure 1. Furthermore, it was assumed that the produced water stays in the concave portions on the catalyst layer, and stripe-shaped projections were formed on the channel cover to prompt drainage of the produced water from the fuel channels.

The transparent fuel channel cover was fabricated with PDMS using soft lithography techniques. Initially, a mold for the cover was made with a dry film resist. Micro stripe pattern with 40μm width were made. Considering the PDMS shrinkage during polymerization, the mold pattern had to be formed a few percent larger than the desired shape. Figure 2 shows the whole view of the PDMS channel cover on a miniature fuel cell with Si electrodes. The reaction on the Si substrate was 1mm and 4mm long. Within the area, 100μm x 100μm sections were etched down to the backside catalyst layer. Magnified view on the reaction area is shown in figure 3. It was found that the stripes were finely aligned on the concave portions on the Si electrode.

Figure 4 shows the polarization curves of the power generation tests. Results with the novel fuel channel cover with stripes showed higher output compared to the conventional simple cuboid straight shape cover. Figure 5 shows the microscopic view of the channel. While produce water droplets were observed on downstream area in the conventional cuboid shape channel, no droplets were observed with the novel channel cover. It was assumed that drainage of the produced water was successfully prompted and smooth fuel supply to the catalyst layer was realized by the novel fuel channel cover.

Acknowledgement

This work was partly performed under the Cooperative Research Program of “NJRC Mater. &Dev.”

References

[1] M. Kobayashi, T. Suzuki, M. Hayase, Journal of Power Sources, 267, 622-628 (2014).

[2] R. Shirai, et al., Journal of The Electrochemical Society, 166(15), D834 (2019)

Figure 1
Investigating the Suitability of Printed Circuit Components for Fuel Cells
Authors: Garsany Yannick , Cronin Kevin , Bethune Keith , Stroman Richard
Published: February 2024

Flexible electrochemical energy sources using non-traditional cell materials and topologies have attracted growing attention because they offer unique design opportunities that are still being explored. They also offer potential advantages such as conformability, high power density, high specific power, and low cost through the adoption of electronics manufacturing techniques. This study examines the feasibility of using flexible printed circuits boards (PCBs) as the anode and cathode current collectors (CCs) of single cell Proton Exchange Membrane Fuel Cell (PEMFCs). In this work, we determine the best anode and cathode interfaces at which to embed flexible CCs to obtain the highest power, as illustrated in Figure 1. The flexible anode and cathode CCs are embedded A) inside the PEM|Catalyst Layer (CL) interface, B) between the CL|Micro Porous Layer (MPL) interface and C) between the Gas Diffusion Layer (GDL)| Flow field (FF) interface. The performance of the single cell PEMFC with the embedded flexible anode and cathode CCs at the different interfaces described in Figure 1 is investigated by using I-V polarization curves, electrochemical impedance spectroscopy (EIS), and thermal imaging. The performance of the cells tested with the embedded flexible CCs is compared to the performance of a standard cell. This study also investigates the effect of varying the anode and cathode CC geometry (square shape vs. circular) and opening ratio (20%, 30%, 40%, 50% and 60%) on the cell performance.

Figure 1
Casting Electrodes on PEEK Reinforced Sulfonated Polyphenylsulfone Membrane
Authors: van Treel Niklas , Qelibari Regina , Titvinidze Giorgi , Klose Carolin , Münchinger Andreas , Cruz Ortiz Edgar , Vierrath Severin
Published: February 2024

Researchers are exploring the potential of proton exchange membranes made from hydrocarbon polymers that do not contain fluorine. These polymers possess desirable properties that could make them more environmentally friendly and cost-effective compared to current perfluorinated sulfonic acids (PFSA). Hydrocarbon polymers have a unique structure that maintains high proton conductivity while reducing gas crossover, thus presenting a promising alternative to PFSA membranes [1]. Previous studies have demonstrated the potential of hydrocarbon membranes in electrolyzers using sulfonated polyphenylene sulfone (sPPS) [2]. However, sPPS has a high ion exchange capacity (2.17 – 3.57 meq/g), leading to excessive water uptake that causes the membrane to swelling and impedes upscaling, such as casting anodes directly onto the membrane. To overcome this issue, a woven, open-mesh PEEK substrate was incorporated into the membrane. The reinforced membrane exhibited a significant reduction in water uptake of up to 53% at room temperature and 43% at 60°C compared to the initial membrane. This improvement made it possible to cast the anode directly onto the membrane, resulting in a homogeneous surface (Fig. 1 left). In addition, preliminary electrolysis tests showed promising performance with low membrane resistance of 69 mΩcm² for a 74 µm thick membrane (Fig. 1 right).

Literature: [1] Miyake, J.; Taki, R.; Mochizuki, T.; Shimizu, R.; Akiyama, R.; Uchida, M.; Miyatake, K. Design of flexible polyphenylene proton-conducting membrane for next-generation fuel cells. Sci. Adv.
2017, 3(10), eaao0476. DOI: 10.1126/sciadv.aao0476

[2] Klose, C.; Saatkamp, T.; Münchinger, A.; Bohn, L.; Titvinidze, G.; Breitwieser, M.; Kreuer, K.; Vierrath, S. All‐Hydrocarbon MEA for PEM Water Electrolysis Combining Low Hydrogen Crossover and High Efficiency. Adv. Energy Mater.
2020, 10 (14), 1903995. DOI: 10.1002/aenm.201903995

Figure 1
Design of Bipolar Membranes to Increase CO Formation Rates in Bicarbonate Electrolysers at Low Voltage
Authors: Williams Aubry S. R. , Mowbray Benjamin A. W. , Lu Xin , Kim Yongwook , Berlinguette Curtis P.
Published: February 2024

The electrolysis of bicarbonate solutions offers a direct route for converting alkaline CO2 capture solutions into value-added products. Alkaline CO2 capture exploits the reaction of CO2 with OH- to form aqueous HCO3-, which can be converted back into CO2 in-situ ( i-CO2) by protons sourced from a bipolar membrane (BPM). Bicarbonate electrolysis is currently too energy intensive to be economically viable, with the largest energy input coming from the voltage drop across the membrane. BPMs are usually thicker than monopolar membranes, causing high Ohmic losses and limited water transport to the water dissociation junction. This causes the membrane to dry out and require excessively high voltages to operate at high current densities. To date, little research has been directed towards designing BPMs for bicarbonate electrolysis. Our work focuses on designing BPMs with low voltage drops while keeping the amount of i-CO2 suppliedto the cathode high. In this study, we present custom-made BPMs that enable bicarbonate electrolysis at a current density of 100 mA cm-2 and a cell voltage < 3 V, with cell voltage remaining < 10 V at current densities in excess of 1 A cm-2. We also demonstrate a correlation between a thicker cation exchange layer and higher i-CO2 generation and elucidate the cause of this phenomenon.
Reinforced Membranes with PTFE Matrix and Sulfonated Hydrocarbon Electrolyte for PEM Fuel Cells
Authors: Pratama Juniko Nur , Lee Hyejin , Shin Dongwon , Bae Byungchan
Published: February 2024

Proton exchange membrane fuel cells (PEMFCs) have emerged as a promising technology for clean energy conversion with various potential applications. Due to its cost-effectiveness, sulfonated hydrocarbon has been researched as an alternative to Nafion, a commercial proton exchange membrane. However, sulfonated hydrocarbon's mechanical and chemical stability remains a critical challenge that needs to be addressed, as the membrane must withstand harsh operating conditions, such as wet-dry mechanisms in high-temperature operations. To compete with perfluorosulfonic acid (PFSA), sulfonated hydrocarbon should be reinforced with a polytetrafluoroethylene (PTFE) substrate. However, there are significant issues with incompatibility between sulfonated hydrocarbon and PTFE substrate.

To improve the impregnation, simple and reproducible chemical treatment has been developed to enhance the hydrophilicity of PTFE using a mixture of acids and oxidizing agents. Moreover, surfactant was added to increase compatibility and improve impregnation. After the reinforced membrane was fabricated, the membranes were characterized, including their water uptake and dimensional stability. The reinforced membrane also showed superior mechanical properties, including gas permeability, tensile strength, and dynamic mechanical analysis. To evaluate the degree of impregnation, the transparency of the reinforced membrane was checked for haziness and further analyzed with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) mapping to quantify the impregnation degree. Finally, the performance and durability of the reinforced membrane were measured by single-cell and wet-dry cycling tests.
Alkaline-Stable Poly(phenylene-co-arylene ether) Block Copolymer-Based Anion Exchange Membranes with Alkyl Side Chain
Authors: Kwon Hugeun , Lee Hyejin , Shin Dongwon , Bae Byungchan
Published: February 2024

Proton exchange membranes (PEMs) are desirable materials as they can be applied to their potential and wide range of electrochemical applications. However, in most electrochemical applications of PEMs for energy production, precious metals such as platinum are essential as catalysts due to the highly acidic media of the system. Anion exchange membranes (AEMs) have been studied recently to replace these PEMs. However, AEM-based electrochemical devices mainly operate under strongly basic conditions. Under those conditions, AEM is prone to decomposition. As a result, membrane scientists have adopted polymers of ether-free backbone, but their IEC is generally more than 2.0 meq/g to achieve high conductivity. The high IEC results in excessive water uptake, making the AEM fail chemically and mechanically during long-term operations.

To develop high-performance AEMs, we have synthesized new phenylene-based block copolymers. They have phenylene chains as hydrophilic segments for high chemical stability, in which hydrophobic parts are composed of arylene ether. This configuration is beneficial in solubility because the hydrophobic arylene ether block mitigates the poor solubility of phenylene. Moreover, a flexible alkyl chain was introduced as conducting moiety into hydrophilic phenylene. Thus, the enhanced solubility promoted the membrane’s efficient hydrophilic/hydrophobic morphological separation. The block copolymer-based AEM showed lower HFR (141 mΩ·cm2) than the Fumatech membrane (168 mΩ·cm2) in single-cell performance at 70 °C.