Freezing conditions pose a major challenge for Proton Exchange Membrane Fuel Cells (PEMFCs), particularly in automotive applications where fast, energy-efficient start-up is essential. Two critical issues arise: (i) internal mechanical degradation of the cells, induced by freeze/thaw cycling, and (ii) the difficulty of cold starting, which directly affects the durability and performance of the system. Ice formation in bipolar plates and catalytic layers leads to delamination and accelerated degradation of the membrane-electrode assembly (MEA), significantly reducing its lifespan [1]. Recent studies report a 2.4% loss in performance after only 3,000 freeze/thaw cycles [2], highlighting the urgent need to develop optimized cold start strategies that minimize energy costs, start-up time, and component degradation [3]. To address these challenges, the PEPR Durasys PAC project proposes a collaborative approach aimed at providing concrete solutions. Within this framework, LEPMI and CEA have developed a methodology combining advanced experimentation and modeling to identify key drivers to improve and to validate robust strategies. In this article, we present more specifically the experimental results obtained, as well as the protocols implemented to characterize the degradation mechanisms under freeze/thaw cycles. Initial tests to investigate the impact of freeze/thaw cycles on PEMFCs are performed between - 20°C and +10°C. The freeze/thaw cycles (out of operation of the fuel cell) are repeated few hundred times. Electrochemical characterizations (during operation) are carried out after the break-in phase and during cycling to monitor any changes in performance: electrochemically active platinum surface area degradation, ionic resistance and mass transport increase thanks to polarization curve, Cycling Voltammetry and impedance spectroscopy measurements. High humidity conditions of 95/95RH are used to submerge the cell and exacerbate potential damage related to freezing/thawing. As shown in Figure 1, no significant cell performance degradation is observed after two hundred cycles. Freeze/thaw cycles are ongoing to go further in the aging study. Nevertheless, this unexpected result does not rule out the possibility of microstructural changes within the MEA and its components. In order to identify and characterize these potential degradations, post-mortem morphological analyses of MEAs are planned, targeting in particular interface delamination, membrane ruptures, and electrode alterations. In addition, an in-depth study of materials and interfaces is underway to elucidate the underlying mechanisms. A dedicated experimental platform will enable passive hydrothermal cycles (without active gases) to be carried out, both ex-situ and in-situ , in order to stress the components and MEAs. Physicochemical and morphological characterizations, such as X-ray microtomography and interface analysis, will be used to identify failures at the micrometric (delamination) and nanometric (electrode alteration) scales. In addition, the development of peeling methods will enable the quantification and characterization of interface properties. Finally, the properties of the materials, depending on temperature, relative humidity, and number of cycles, will be compared between MEAs aged under real-world and laboratory conditions. References: [1] E. Pinton et al., ECS Transactions, 2009, pp. 251-261. [1] Y. S. Kim et al., Int J ofHydrogen Energy, 2015, pp. 360-399. [2] A. Amamou et al., IEEE Transactions on Vehicular Technology 2020 (99) pp. 1-1. Figure 1

With the increasing development of Proton Exchange Membrane Fuel Cell (PEMFC) technology in recent years, the recyclability of aged Membrane Electrode Assemblies (MEAs), is becoming an important issue to address. Up to now, the main studies dealing with PEMFCs recycling have mainly focused on the recovery of rare and precious materials (e.g. platinum (Pt)) contained in the catalyst layers (CL). However, the PFSA (Perfluorinated Sulfonic Acid) ionomer membrane is another essential and value-added PEMFCs component that must be included in the recycling process in order to both reduce its manufacturing costs (related to the complex fluorine chemistry) and its environmental impacts at the end of their life (EoL). Current EoL technologies for platinum recovery from MEAs are either based on hydrometallurgical or pyro-hydrometallurgical processes, and offer high recovery yields. However, they have two major drawbacks: they do not allow direct recovery of the ionomer membrane and, in the case of pyrometallurgy, they involve the release of a significant quantity of highly corrosive and toxic hydrogen fluoride (HF) gas due to the membrane incinerationWith this in mind, different routes for the separation of membrane electrodes from end-of-life MEAs, which constitutes the first step in the recycling of ionomer membrane, is investigated in this study 1 (Figure1). To monitor the process of membrane-electrodes separation, a specific methodology based on ultraviolet (UV-Vis) spectroscopy and optical microscopy is first set up.. Subsequently, the quality of the components separation is monitored through the establishment of a material balance thanks to thermogravimetric analysis (TGA). A two-step process, based on the use of diluted isopropyl alcohol (IPA) solutions under stirring, is proposed as an efficient and environmentally friendly method for the effective separation of the electrodes from the ionomer membrane. This process offers a high yield recovery (up to 95 % for PFSA), a low energy consumption and the avoidance of harmful gases emission. At a first stage, the physical separation of membrane and electrodes is carried out under mild temperature (40 °C), allowing to recover carbon, Pt and ionomer binder on one side and the PFSA ionomer membrane on the other side. The further dissolution of the PFSA ionomer membrane at a higher temperature (75 °C) in a second stage enables the recovery of a PFSA ionomer dispersion. The most promising processes are tested on both pristine and various samples of aged MEAs to demonstrate the robustness of the methodology regardless of the ionomer membrane type and aging state. The hydroalcoholic ionomer solutions resulting from EoL MEAs recycling have interesting potential for reuse in a variety of applications, such as in purification technologies (e.g. pervaporation, ultrafiltration). Reference: (1) M.Robert et al., Energy Fuels 2025, 39, 5, 2758–2771 Figure 1

Des films polymères multicouches sont caractérisés par microscopies Raman et Infrarouge, offrant des détails sur leur structure, composition et vieillissement. La combinaison de ces deux techniques permet de comprendre les interactions entre polymères, les changements moléculaires et les réponses aux contraintes environnementales. Les sensibilités des techniques sont comparées pour différentes fonctions chimiques. La microscopie Raman offre une meilleure résolution spatiale pour les profils d’oxydation.

Proton exchange membrane fuel cells (PEMFCs) are a promising technology for automotive applications. The membrane electrode assembly (MEA) remains the most vulnerable element in fuel cells due to its membrane composed of perfluorosulfonic acids. Over the lifetime of the PEMFC, cation contamination occurs from corrosion of fuel cell stack components such as bipolar plates and could be concentrated at particular locations. These cations can migrate from the bipolar plate into the electrode and the membrane. Indeed, due to their affinity toward sulfonic groups, they tend to replace protons affecting membrane conductivity. In addition, some ionic species such as iron cations are commonly known as catalysts for the Fenton reaction responsible for the chemical degradation of the membrane. In this work, we investigate the local effect of ferric contamination and its diffusion through electrochemical tests and post-mortem analyses. A membrane is strategically contaminated by Fe 3+ ions, then assembled into MEA using a hot-pressing method. A segmented cell monitors the ferric ion impact on local cell performance and impedance parameters at different operating conditions. After in-situ tests, MEA’s membrane and gas diffusion electrodes (GDE) are separated for analysis. Then, iron species are quantified to visualize the migration of Fe 3+ in both in- and through-plane directions. Post-mortem analysis suggests that at high local contamination, a part of cations is leached from the contaminated regions of the membrane after a PEMFC operating (Figure 1). In terms of cation distribution, post-mortem analyses reveal a preferential diffusion of Fe 3+ perpendicular to the gas diffusion channels and in the flow direction of H 2 . On a local scale, performances of contaminated channels are affected especially at low hydration levels Besides the in-plane diffusion the propagation of cations from the membrane to electrodes has been detected, at rates approaching 25% of total contamination. The impact of the Fe 3+ migration on radical scavenger diffusion is discussed. Our results provide useful information about cation diffusion in complex systems such as MEAs and gives us some hints on recovery protocols to extend lifetime of fuel cells. Figure 1

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

This paper investigates how cell manufacturing defects can propagate within healthy areas of the same cell or to adjacent cells within a stack. To do so, a defective stack is assembled on the basis of 30 cells without defect and 5 defective cells with controlled lack of anode catalyst layer. The analysis of the degradation rate showed that the adjacent cells to the defective cells are the ones whose performance degraded the fastest, which implies that the presence of defects within the stack induces a propagation of the performance decrease. Post-mortem analyses are performed in the vicinity of the anode defect in the adjacent cell and highlight a significant degradation of perfluorosulfonic acid (PFSA) inducing hydrogen leakages through the membrane. The propagation of the degradation of the membrane in the surroundings of the anode defect to the adjacent cell can be discussed based on the stack design and operating conditions.

Defects in the various components of the membrane-electrode assembly (MEA), initially present or created during aging, are known to be responsible for the short lifetime PEMFC. Catalytic layer degradation has been identified as one of them [1]. However, the possible propagation of these defects to other components within a cell or a stack is not clear in the literature. To shed light on these phenomena, customized MEAs with a localized lack of anode active layer at two different locations -near the hydrogen inlet or outlet- were manufactured and tested with specific accelerated aging tests, combining high and low current and humidity cycles; these were specifically tailored to observe a possible propagation of the defects [2]. Local performance monitoring using a segmented cell revealed variations within the catalytic layers upstream and downstream of the defect. In order to better understand the impact of anode active layer defects on MEA components, localized physicochemical analyses were performed post mortem along the gas flow, with the main objective to identify possible degradations of the reinforced perfluorosulfonic acid (PFSA) membranes. Microscopic thickness measurements showed significant membrane thinning in the defective segments. Difference of these localized degradations between the monopolar plates rib and channel zones will be highlighted depending on the defect location i.e. at the inlet and outlet of hydrogen flow (Figure below). In the defective area, decrease of the Ion Exchange Capacity estimated by Raman analyses is pointed out for the reinforced PFSA layer. The PFSA chain degradation mechanism will be discussed, and, thus, the degradation rate will be calculated based on Raman and FTIR microscope and 19 F NMR. For longer ageing time, the ionomer degradation is extended to an non-defective area. A propagation mechanism of the degradation will be proposed. [1] L, Dubau, et al. WIREs Energy and Environ. 2014 , 3 , pp. 540-560. [2] S, Touhami, et al. J. Power Sources. 2021 , 481, pp. 228908-228917. Figure 1

Perfluorosulfonic acid (PFSA) membrane degradation has been identified as one of the main factors responsible for the short lifetime of PEMFCs [1,2]. The aging mechanisms of these membranes are complex due to mechanical fatigue combined to chemical aggressions. Mechanical fatigue results from the wetting/drying cycles while the chemical aggressions are induced by radicals formed during fuel cell operation. Although it is commonly accepted that chemical and mechanical stresses can interact to accelerate membrane degradation [3], coupled studies are rarely conducted. Thus, an original experimental set-up to perform ex-situ aging tests combining membrane exposure to cyclic mechanical stresses to a free radical environment under conditions close to those observed during cell operation has been developed [4]. Ex-situ aging was performed on PFSA membranes reinforced (Nafion™ XL) with a cyclic compression oscillating between 0 - 10 MPa (0.1 Hz frequency) and a Fenton solution containing 1 ppm Fe2+ and 3 %vol H2O2. Such stresses revealed a significant morphological alteration with the appearance of “bubbles” close to the surface membrane (Figure 1, left). No chemical structure modification was detected within the three different layers. Nevertheless, SEM-EDX, FTIR and Raman microscopic analyses highlight delamination close to the reinforcement/PFSA interface (Figure 1, rigth). Additional peeling tests argued this failure point in the Nafion™ XL membrane. Figure 1

Defects-propagation in polymer electrolyte membrane fuel cells membrane electrode assemblies (MEA) is investigated via Accelerated Stress Tests (AST) combining load (hence potential) and load-driven humidity cycling, and open-circuit voltage. Customized MEA with lack of anode catalyst layer at two different locations-near the hydrogen inlet or outlet-are fabricated and subjected to the AST. Periodical electrochemical characterizations are performed using a segmented cell, enabling to track the cell performance and anode/cathode electrochemical surface area (ECSA) over the test period with a spatial resolution along the gas channels. These observations are completed by post mortem analyses of the MEA. The MEA accelerated degradation is obvious, with multiple impacts on the cell performance and materials. More specifically, the results brought first evidence of defects propagation, in term of anode ECSA loss, in the direction of the hydrogen flow. The cathode ECSA is also impacted, although seemingly homogeneously. Significant membrane thinning is observed for the defective segments, without propagation to the adjacent ones. Anode and cathode local potential monitoring during the AST reveals the absence of cathode high-potential excursion, in both the segments with/without initial defects: the membrane and anode accelerated degradation is governed by chemical mechanisms like gas crossover rather than electrochemical mechanisms induced by high-potential excursions.

Defects known to shorten the lifetime of polymer electrolyte membrane fuel cells (PEMFC) can appear on different membrane electrode assembly (MEA) components and under different forms due to manufacturing processes or operational aging of the fuel cell [1, 2]. Defects-propagation in polymer electrolyte membrane fuel cells membrane electrode assemblies (MEA) is investigated via Accelerated Stress Tests (AST) combining load (hence potential) cycling, load-driven humidity cycling, and open-circuit voltage. Customized MEA with lack of anode catalyst layer at two different locations -near the hydrogen inlet or outlet- are fabricated and subjected to the AST. Periodical electrochemical characterizations are performed using a segmented and instrumented cell, enabling to track the cell performance and anode/cathode electrochemical surface area (ECSA) over the test period with a spatial resolution along the gas channels. These observations are completed by post mortem analyses of the MEA. The MEA accelerated degradation is obvious, with multiple impacts on the cell performance and materials. More specifically, the results brought first evidence of defects propagation in terms of membrane thinning and anode ECSA loss: significant membrane thinning is observed for the defective segments, while anode ECSA loss is measured downstream in the direction of the hydrogen flow. The cathode degradation is poorly affected by the presence of the anode defects. In addition, membrane degradation also appears to propagate downstream the channels when the AST is prolonged for a long period of time. Anode and cathode local potential monitoring during the AST reveals the absence of cathode high-potential excursion, in both the segments with/without initial defects. However, oxygen crossover -toward the hydrogen compartment- is probably detected through slight variations in the anode local potential: this lead to the conclusion that the membrane and anode accelerated degradations are seemingly governed by chemical mechanisms like gas crossover rather than electrochemical mechanisms induced by high-potential excursions. Guilminot, E. et al. Membrane and Active Layer Degradation upon PEMFC Steady-State Operation. J. Electrochem. Soc. 154, B1106 (2007). Dubau, L. et al. A review of PEM fuel cell durability: Materials degradation, local heterogeneities of aging and possible mitigation strategies. Wiley Interdiscip. Rev. Energy Environ. 3, 540–560 (2014). Figure 1

The hydrolytic stability of poly(ethylene terephthalate) (PET) has already been largely reported. The chemical reactions induced by damp-heat exposure are well-known, and various kinetic expressions for the degradation have been presented. Using the data from previous studies, a new model for degradation is proposed. This model combines the effect of temperature and humidity in a single equation. Three parameters are utilized: the classical pair of activation energy (Ea) and pre-exponential factor (f(0)), and the reaction order (n) to the relative humidity (RH). The model may be used to fit the degradation data from various sources describing the hydrolysis over a large range of conditions (40-100 % RH, 60-160 degrees C). In addition a prediction of the crystallinity changes brought about by hydrolytic chain scission was performed. Prediction of useful lifetime in moist heat is also possible (hydrolysis of 0.2% ester moieties in the polymer). (C) 2018 Elsevier Ltd. All rights reserved.

The effect of proton exchange membrane fuel cell (PEMFC) operation on physicochemical properties and roughness of gas diffusion layers (GDL) was evaluated in this work. In addition to static contact angle measurements commonly used for GDLs, sliding angle measurements were also performed on a membrane electrode assembly (MEA) both new and used in service within commercial PEMFC. These latter revealed significant changes after 4,000 h in service that were not detectable with the static counterparts. The main novelty of this study is to correlate the contact and sliding angle measurements and to combine them with various modeling approaches developed for modeled surfaces. After 4,000 h of aging, it was thus shown that the surface of the GDLs became more hydrophilic, contrary to the roughness, which remains unchanged.

Mechanical toughness and high barriers to air and water may be combined in a polymer-metal multilayer film, provided that the two materials are properly bonded together. Delamination is indeed the most severe flaw observed in service. This suggests that the polyurethane (PU) adhesive at the polymer-metal interface fails to bear the shear forces, as happens principally if a multilayer system is submitted to elevated temperature and humidity. A Raman microscopy of the multilayer revealed a cohesive delamination, with glue on both the surfaces. A detailed investigation of the kinetic of degradation of the polyester was therefore carried out. IR spectroscopy of the standalone PU film hydrolyzed in a controlled manner furnished a series of aging markers. The reference curve was established for approximately a year in continuous severe aging conditions. This curve could be further used to compare the amount of degradation in real systems in a wide range of conditions and time. Moreover, at the metallized interphase, a complex with a free hydroxyl group was detected. The content of this AlIII complex based on terephthalate or carbamate increases with the progress of the ester hydrolysis reactionin the layer.

The degradation of perfluorinated sulfonic acid ionomer (PFSA) binder in catalyst layer of Proton Exchange Membrane Fuel Cell (PEMFC) was investigated on Membrane-Electrode Assemblies (MEA) operated up to 10400 h in base load conditions for telecom relay. Soxhlet extractions in water media were performed on the catalyst layer deposited on the Gas Diffusion Layer (GDL). The Soxhlet solutions for anode and cathode sides were analyzed by F-19 NMR spectroscopy showing degradation products originating from the ionomer in the catalyst layer. At the cathode side, 1,2,2-tetrafluoro-2-(1,2,2,2-tetrafluoroethoxy)ethanesulfonic acid were clearly identified. This suggests that PFSA binder degradation originated from an H center dot and/or center dot OH radical attack of the side chain. The NMR quantification of the degradation products allows a fruitful comparison with the literature. The degradation mechanism of the PFSA binder is different from that of the membrane. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.