Membrane Durability Research Articles

Phosphate-grafted polyethyleneimine-induced multifunctional cerium oxide as an antioxidant for simultaneously enhancing the proton conductivity and durability of proton exchange membranes

Phosphate-grafted polyethyleneimine-induced multifunctional cerium oxide as an antioxidant for simultaneously enhancing the proton conductivity and durability of proton exchange membranes

Effects of channel structure at inlet region on temperature distribution of proton exchange membrane fuel cells

Enhancing the temperature distribution uniformity in membrane electrodes is crucial for improving the durability and performance stability of proton exchange membrane fuel cells. In this study, we discovered an entrance region in the cathode membrane electrode of proton exchange membrane fuel cells characterized by a rapid rise in temperature. This inlet region shows a notably higher temperature variation rate compared to other regions. This phenomenon is attributed to the temperature difference between the constant temperature fluid supplied by the channel inlet and the heat generation in the cathode catalyst layer. Thus, the impact of channel structure at the entrance region on the temperature distribution of the cathode catalyst layer is investigated, based on a three-dimensional, non-isothermal, two-phase model. Results show that boosting heat transfer in the inlet region is more effective for reducing the average temperature than in other regions. We proposed five kinds of step arrangement schemes and discovered that the step arrangement in the entrance region of the cathode flow channel can increase the temperature uniformity of the cathode catalyst layer by 9.71% without net power loss. Furthermore, this study examines the impact of length, height of entrance steps, and outlet channel height on heat transfer and identifies the optimum value. When severe water flooding occurs, the gas purge coupled with the step-fronted scheme is essential for improving temperature uniformity.

A novel approach using a stacked layer filtration process to desalination from cotton fabric and conductive graphene sheets

ABSTRACT Given the growing water scarcity problem, desalination of seawater offers a promising solution for obtaining potable water. While various methods have been used in the past, membrane technology remains the leading approach. However, challenges persist, including high operational costs, limited membrane durability, and susceptibility to fouling, which require effective management solutions. Graphene oxide membrane desalination and solar desalination have made substantial advancements in converting salt water into fresh water in recent years. This study utilized artificial sea water (ASW) derived from different salt mixes as the primary source for desalination. Two filters were prepared with cotton fabric and conductive graphene sheets, layer by layer. This experimental approach of stacked layer filtration (SLF) desalination demonstrated favorable outcomes, as an outcome of chloride removal has been achieved in all samples. When using ASW samples diluted at a ratio of 20:1, SLF-I was able to remove 42.86% of chloride, whereas SLF-II removed 57.14%. It was observed that the fabric could be cleansed by hand to remove salts that had accumulated as a result of evaporation, thereby making it reusable. At the same time, no swelling was observed in the conductive graphene sheet.

Novel activated biochar-enhanced superhydrophilic nanofibrous membrane for superior oil-in-water emulsion separation

In this research, a high-performance Polyamide 6/Polyvinyl Alcohol/Activated biochar (PA6/PVA/AB) composite nanofibrous membrane was developed for effective separation of oil-in-water emulsions. The membrane was produced by blend electrospinning of Polyamide 6 (PA6), Polyvinyl Alcohol (PVA), and Activated biochar (AB) derived from peanut shell biomass. Glutaraldehyde (GA) cross-linking was applied to enhance stability in aqueous environments to prevent PVA swelling. The resulting nanofibrous membrane exhibited a cost-effective design with a superhydrophilic/underwater superoleophobic surface (WCA of 0° and UWOCA of 164°), a porous structure (93% porosity), and robust mechanical properties (Tensile strength: 7.73 MPa, Young modulus: 45 MPa). Optimization of the membrane composition, with 5%wt. PVA and 2%wt. AB relative to the total polymer weight in the electrospinning solution, yielded a superhydrophilic membrane capable of withstanding 2 bar pressure. Pure water flux measurements in the pressure range of 0.5–2 bar demonstrated a high permeability of 1727.5 LMH/bar and a pure water flux of 3455 LMH. The PA6/PVA/AB composite membrane exhibited exceptional performance in separating non-surfactant (NS) and surfactant-stabilized (SS) toluene-in-water emulsions (separation flux: 2006 LMH, oil rejection: 99.52%). Furthermore, it demonstrated high efficiency in the separation of SS oil-in-water emulsions of different types of oil (separation flux >1800 LMH, oil rejection >98%). The membrane's durability and chemical stability were confirmed through 15 cycles of oil-in-water emulsion separation, showcasing anti-fouling properties and reusability (separation flux >833, Oil rejection >97%). Considering its superior performance in oil-in-water emulsion separation and robust reusability, the developed nanofibrous membrane holds significant promise for practical applications.

Airfoil flow field for proton exchange membrane fuel cells enhancing mass transfer with low pressure drop

Optimal configuration of bipolar plate (BP) embedding flow field is of great significance in improving the power density and durability of proton exchange membrane fuel cells (PEMFCs). Inspired by the airfoil in aircraft dividing the airflow into two streams causing pressure difference, a novel airfoil flow field (AFF) is designed to enhance the mass transfer capacity in channel and across the rib between two adjacent channels, which hardly increases the pressure drop in channel, unlike many baffle designs. The performance improvement achieved by implementing AFF in PEMFC is compared with common parallel flow field (PFF) and the wave flow field (WFF) by experimental test with respect to polarization curve and electrochemical loss and numerical simulation via a three-dimensional (3D) PEMFC model. The experimental results indicate that the novel AFF exhibits best fuel cell performance at various operation conditions (e.g. relative humidity, air stoichiometric ratio) mainly benefitted from the enhanced oxygen transfer, which contributes to the improvement of maximum power density by 8.85 % and 14.37 % compared to PFF and WFF, respectively. The modeling results indicate that the pressure drop increase in AFF is negligible compared with PFF, and is even slightly lower than WFF, indicating high practicability. Moreover, the utilization of AFF also helps the uniformity of oxygen concentration, current density and temperature in PEMFC.

Systematic experiments and multiscale simulation calculations reveal chemical stability differences in dry/wet nanofiltration membranes

This study investigated the chemical stability differences between dry and wet nanofiltration membranes when immersed in strong acid and base environments. Systematic experimental studies were conducted on both types of nanofiltration (NF) membranes, supplemented by Molecular Dynamics (MD) simulations and Density Functional Theory (DFT) calculations. The results indicate that wet NF membranes, soaked in deionized water for a week, exhibit higher chemical stability compared to dry membranes treated only with air. Traditional air heating causes membrane pore contraction and excessive crosslinking. However, after a week of immersion in water, the polyamide (PA) layer gradually becomes a loose and well-extendable PA layer. MD simulations revealed that H+ and OH− ions possess lower diffusion coefficients and extended residence times in dry NF membranes, making them more prone to damage. Additionally, DFT calculations disclosed that the Gibbs free energy (ΔG) for amide bond hydrolysis in wet NF membranes, in the presence of water molecules, is elevated, significantly delaying their hydrolysis rate under extreme conditions. This study highlights the pivotal role of membrane wetness in the chemical durability of NF membranes and offers a novel perspective for improving membrane lifespan and efficiency.

Design and investigation of novel gradient flow fields for proton exchange membrane fuel cell

Ensuring sufficient gas supply and high distribution uniformity are crucial issues in the flow field design to improve the performance and durability of proton exchange membrane fuel cell (PEMFC). However, previous studies often ignore the gas-water distribution variations along the flow direction and adopt identical design for the entire flow field, resulting in unsatisfactory performance. To fill in this gap, this paper innovatively proposes two types of gradient flow field (gradient narrowing and gradient droplet) considering the gas-water distribution characteristics. The channel of the gradient narrowing flow field gradually decreases in all directions along the flow direction, and the gradient droplet flow field is composed of staggered droplet blocks, and the distribution density gradually decreases along the flow direction. The Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) method is used for the comprehensive evaluation of flow fields. The results demonstrate that the gradient flow field can significantly improve the performance and physical field distribution. The gradient narrowing flow field has the best performance, with 11.39 % improvement in peak power density, 77.96 % increment in average oxygen mass fraction, and 43.11 % improvement in oxygen uniformity compared to parallel flow field. Further, the key geometric parameters sensitivity analysis of gradient narrowing flow field is carried out. This study contributes to understanding the underlying mechanism of mass transfer properties in the novel gradient flow field, and exploring its potential for high-performance flow fields design.

Unveiling the resistance component on fuel cell electrodes by ionic liquid adsorbed PtCo/C catalyst through distribution of relaxation time

A majority of studies focus on developing oxygen reduction reaction (ORR) catalysts and cathode configurations to enhance the performance and durability of polymer electrolyte membrane fuel cells (PEMFCs). In this study, resistance analyses of the membrane electrode assembly (MEA) are conducted to elaborate on the performance and durability improvements induced by the adsorption of [MTBD][beti] ionic liquid (IL) on the commercial PtCo/C catalyst. The morphological changes caused by IL adsorption are observed on micro and macro scales via physicochemical methods. From the half-cell measurement, when the 4 wt% IL was adsorbed, a 15 mV improvement in ORR activity occurred, and as the adsorption amount increased, the activity decreased. The MEA using 8 wt% IL adsorbed catalyst outperforms 1.7 times higher current density at 0.8 V and 40 % lower charge transfer resistance. Distribution of relaxation time resistance analysis reveals that oxygen mass transfer resistance (Rmass), ORR charge transfer resistance (RORR), and proton charge transfer resistance (Rproton) decrease due to IL adsorption. During accelerated durability tests, IL 8 % MEA showed a 58 % increase in durability, and a lower degradation of RORR and Rproton encouraged improved durability. The resistance analyses in this study contribute to identifying the factors responsible for the performance and durability enhancement of PEMFC.

Enhanced antifouling and separation capabilities of polydopamine@Ce-MOF functionalized PES ultrafiltration membrane

The need for antifouling membranes is substantial due to fouling’s negative impact on the effectiveness and durability of ultrafiltration membranes. In recent times, Metal-Organic Frameworks (MOFs) have emerged as effective additives for crafting ultrafiltration (UF) membranes. However, to harness their benefits and mitigate their drawbacks, a well-considered approach is imperative. In this work, polyethersulfone (PES) UF membranes were tailored with polydopamine (PDA)-modified cerium (Ce)-MOF (PDA@Ce-MOF) to achieve satisfactory antifouling properties and to remove biological macromolecules such as bovine serum albumin (BSA) and humic acid (HA) from wastewater. The non-solvent induced phase separation (NIPS) method was used to simultaneously fabricate the membrane and modify it with different PDA@Ce-MOF concentrations ranging from 0.05 to 0.50 wt.%. Results showed significant improvements on the membrane’s morphology, hydrophilicity, porosity and pore size at 0.10 wt.% loading of PDA@Ce-MOF. The synergistic effect of the PDA and Ce-MOF on the membrane improved the pure water flux (337 L m−2 h−1) and filtration performance in the filtration of Bovine serum albumin (BSA) and humic acid (HA) reporting 145 L m−2 h−1 and 98% rejection, and 164 L m−2 h−1 and 88% rejection; respectively. Further, water-attracting functional moieties of PDA@Ce-MOF hindered the deposition of BSA protein on the membrane surface, resulting in an excellent flux recovery ratio (FRR) of ~87%, alongside mitigated irreversible fouling.

Two-phase flow dynamics study in the trapezoidal gas channel of PEM fuel cell based on lattice Boltzmann model

ABSTRACT Water management is a critical challenge in ensuring the performance and durability of low-temperature proton exchange membrane fuel cells (PEMFCs). This study utilizes the phase-field lattice Boltzmann method to conduct three-dimensional numerical simulations, investigating the dynamics of two-phase flow in the cathode gas channel (GC) of PEMFC with a trapezoidal cross-section. The effects of the water inlet location, the surface wettability of GC, the open angle of GC, and the air velocity on liquid water distribution and discharge are analyzed. The results indicate that positioning the water inlet in the middle of the GC significantly enhances PEMFC performance while having minimal impact on average pressure drop. A wall contact angle of 70° or 110°Can optimize fuel cell performance from different directions. Setting a wall contact angle at 70° optimizes gas flow stability and maintains a low-pressure drop value for the GC. A wall contact angle of 110° focuses on optimizing gas reactant diffusion ability into porous electrodes and GC drainage rate. An opening angle of 55° for the trapezoidal gas channel improves overall fuel cell performance. Increasing air velocity facilitates the film flow formation of liquid water on top wall surfaces within the GC.

Effects of gradient structures of cathode catalyst layers on performance and durability of proton exchange membrane fuel cells

Improving performance and durability of proton exchange membrane fuel cells (PEMFC) is crucial for promoting commercial applications. Deep understanding of the underlying degradation mechanisms is still lacking. In this study, a two-way coupling performance-degradation model is established by incorporating one-dimensional (1D) Platinum (Pt) degradation model into 1D PEMFC performance model, which can predict Pt degradation phenomenon considering Pt dissolution, Pt2+ diffusion and reprecipitation in cathode catalyst layers (CCLs) and resulting performance loss. Effects of gradient CCL structures in terms of ionomer weight, Pt loading and Pt particle size on degradation and performance are investigated. The results show that multi-layer CCLs with more ionomer, more Pt loading, and/or smaller particles near membrane have higher performance, while the opposite gradients present enhanced anti-degradation capacity. Wave-like spatial distributions of Pt mass retention are observed in gradient CCLs, with significant difference across the sub-layer interface. Combined effects of two gradient distributions are also investigated. It is found that for performance, simply add-up roles are followed, namely combining two gradient distributions with higher performance can obtain higher performance, and vice versa. For durability, synergy effects are identified, in which two gradient structures with opposite final Pt mass distribution have competitive influence on Pt2+ local transport, with local Pt2+ diffusion suppressed, the catalyst distribution uniformity improved and performance loss alleviated. The gradient CCL structure considering the balance of performance and durability is identified based on 28 structures studied. Such add-up roles for performance and synergy effects for durability provide new insights for improving the design of PEMFCs.

Confined Nano-Channels Incorporated with Multi-Quaternized Cations for Highly Phosphoric Acid Retention HT-PEMs.

Developing a new strategy to retain phosphoric acid (PA) to improve the performance and durability of high-temperature proton exchange membrane fuel cell (HT-PEMFC) remains a challenge. Here, a strategy for ion-restricted catcher microstructure that incorporates PA-doped multi-quaternized poly(fluorene alkylene-co-biphenyl alkylene) (PFBA) bearing confined nanochannels is reported. Dynamic analysis reveals strong interaction between side chains and PA molecules, confirming that the microstructure can improve PA retention. The PFBA linked with triquaternary ammonium side chain (PFBA-tQA) shows the highest PA retention rate of 95%. Its H2/O2 fuel cell operates within 0.6% voltage decay at 160°C/0% RH, and it also runs over 100h at 100°C/49% RH under external humidification. This combination of high PA retention, and chemical and dimensional stability fills a gap in the HT-PEMFC field, which requires strict moisture control at 90-120°C to prevent acid leaching, simplifying the start-up procedure of HT-PEMFC without preheating.

Dynamic modeling of chemical membrane degradation in polymer electrolyte membrane fuel cells: Effect of precipitated Pt particles

Chemical membrane degradation in polymer electrolyte membrane fuel cells operated under real conditions is often accompanied and affected by Pt catalyst degradation. This study investigates the effects of both artificially impregnated Pt particles and Pt migration on chemical membrane degradation are numerically investigated. For the first time, the impact of Pt migration is numerically analyzed. Membrane structural changes with coupled chemical membrane and Pt degradations are proposed. For Pt particles that are artificially impregnated in the membrane, yielding a Pt content of up to 50 mol% Pt, the membrane degrades at the fastest rate at moderate Pt contents (2 mol% Pt). The impregnated Pt particles promote the conversion of Fe3+ to Fe2+, which adversely impacts the membrane durability. The decrease in Pt content leads to reduction in both the Fe2+ conversion time and trend. In comparison, the naturally precipitated Pt particles in the membrane from the degraded Pt catalysts in the CL, have demonstrated a Pt content consistently lower than 2 mol% Pt. As a result, the chemical degradation rate of real fuel cells accelerates significantly with increasing Pt particle concentration. The chemical degradation rate increases with the gas solubility at the pore/electrolyte interface. With higher gas solubility, the peak location of chemical membrane degradation shifts from the anode side to the cathode side.

In situ investigation of moisture sorption mechanism in fuel cell catalyst layers

Research focusing on catalyst layers is critical for enhancing the performance and durability of proton exchange membrane fuel cells.

Triazole-rich 3D metal-organic framework incorporated solid electrolytes for superior proton conductivity and durability in fuel cells.

Insufficient proton conductivity and oxidative stability of sulfonated hydrocarbons hinder their applicability as proton exchange membrane electrolytes in fuel cells. In this regard, fabrication of proton conducting mixed-matrix membranes (PC-MMMs) can be a superior approach to obtain desirable properties. In this work, a triazole ligand (1H-1,2,4 triazole) was coordinated to a zinc metal node to create a 3D metal-organic framework (MOF) and incorporated as an additive in a sulfonated poly(ether ether ketone) matrix at 1, 3, and 5 weight percentage to fabricate PC-MMMs by the casting process. Several characterization tools such as electrochemical impedance spectroscopy, Fourier transform infrared spectroscopy and scanning electron microscopy were used to characterise these membranes and study their potential application as electrolyte(s) in PEMFCs (proton exchange membrane fuel cells). Membranes were also tested for water uptake, ion-exchange capacity and oxidative stability in Fenton's reagent. The performance of the polymeric composite membrane containing a 3 wt% MOF was then assessed in a H2/O2 single cell as it demonstrated the highest proton conductivity of 0.04 S cm-1 among all the compositions and a maximum current density of 1191 mA cm-2. The membrane was also subjected to an OCV hold test for 12 hours to study the chemical durability over a period of time. This report establishes that the inclusion of a triazole based MOF enhances the proton conductivity, performance, and thermal and chemical durability of composite membranes which can be considered as a promising electrolyte material at intermediate temperatures after a proper optimisation of different cell parameters.

Examination of Nafion membrane performance with acid-base functionalized graphene oxide.

Functionalized graphene oxide (GO) as a good additive can improve the performance of proton exchange membrane (PEM) via the introduction of various functional groups. How to balance the proton conductivity and durability of membrane based on functionalized GO is a key issue. In this work, benzoic-acid-functionalized GO(BAF-GO) and 1,2,4-triazole-functionalized GO(TF-GO) are employed as doping candidates, and the co-doping effect on membrane performance is investigated by means of experiment and molecular dynamics simulation. Meanwhile, the quantum chemistry method is implemented to explore the interaction between TF-GO, membrane and BAF-GO. The results reveal that the composite membrane exhibits high durability and enhanced proton conductivity. When the doping mass ratio of BAF-GO to TF-GO is 3 : 1, the proton conductivity can be greatly improved, especially under low-humidity conditions. Excessive addition of basic groups does not enhance proton transport.

Current Trend of MOFs Incorporated Membranes for Advanced Wastewater Treatment

Membrane technology has gained attention in wastewater treatment due to its great potential for producing high-grade water products for reuse. The membrane also effectively removes persistent pollutants in water effluent. However, their application is constrained by low productivity due to fouling formation. Incorporating functionalized nanoparticles into polymeric membranes has attracted much attention due to the improved membrane performance and additional features. Metal-organic frameworks (MOFs) incorporated into polymeric membranes have been widely applied in reverse osmosis (RO), forward osmosis (FO), nanofiltration (NF), and microfiltration (MF) for water and wastewater treatment. This short review presented recent findings, fabrication methods, and a systematic understanding of transport mechanisms under various operating conditions. This study also focused on several important parameters, such as improving physicochemical properties, membrane features, and performance enhancement in wastewater treatment. The reported studies show that MOFs incorporated membranes have reached >95% organic pollutants and 100% suspended solids. The membrane durability was also enhanced up to 140%, and the flux recovery can be maintained at 98% after several cycles. Even some MOFs, such as ZIF-8 and UiO-66, exhibited excellent performance in harsh conditions (pH < 4). The prospects and challenges of MOFs-incorporated membranes in industrial applications were also provided in this study.

Impact of GDL Hole on Chemo-Mechanical Membrane Degradation Investigated by 4D in-Situ Visualization

Membrane electrode assembly (MEA) is the core unit of a fuel cell system, which is composed of proton exchange membrane (PEM), sandwiched on both sides by catalyst layers (CLs) and gas diffusion layers (GDLs). The membrane is subjected to various chemical and mechanical stresses during fuel cell operation, and these stresses will cause membrane degradation over time. Also, the interaction between membrane and other fuel cell components such as CLs and GDLs contributes uncertainty to the membrane degradation process. Previous morphological studies [1] on CLs and GDLs discovered common non-uniform features in these materials such as clusters, sags, cracks, and holes. In addition, such features could also appear during the MEAs assembly [1] process. Previous membrane degradation study discovered buckling driven membrane failure [2], which is strongly related to CL or GDL sags, cracks, and holes. Additionally, impinging driven membrane failure was also reported [2], which is caused by clusters and peaks on CL or GDL surfaces. Models were also developed to understand the mechanism of mechanical membrane degradation related to buckling. For instance, Ramani et al. [2] created a model to simulate membrane buckling into GDL surface pores, and identified stress concentration at the buckling center as the root cause of crack formation. Comparing MEAs made with high and low surface roughness GDLs, it was confirmed that GDL with low surface roughness has significant mitigatory impact on mechanical membrane durability. However, to the authors’ best knowledge, the level of impact of such non-uniform features under combined chemo-mechanical degradation, which is the most common form of membrane degradation during regular fuel cell operation, has not yet been reported.In this work, the objective is to understand the specific impacts of GDL holes as they relate or contribute to the combined chemo-mechanical membrane degradation mechanism and associated membrane durability in polymer electrolyte fuel cells. The study was carried out using a four dimensional (three spatial dimensions plus one temporal dimension) in-situ methodology achieved through X-ray computed tomography (XCT) visualization [3], and the MEAs were made of GORE-SELECT® membrane, Pt based CLs, and AvCarb® GDLs with smooth and crack free microporous layer (MPL). Through-thickness circular GDL holes were introduced with multiple controlled sizes at multiple strategic locations, on anode or cathode GDL. The MEAs were custom designed small scale MEAs with 0.39 cm2 active area for in-situ XCT visualization, and the cells were subjected to a custom accelerated stress test (AST) protocol imparting combined chemo-mechanical stresses in an alternating pattern [3]. The graphite endplates had narrower flow field compared to previously used ones [3], which can reduce membrane degradation rate and better deliver compressive stress to the MEA. A baseline MEA without GDL hole was first tested, with only minor membrane thinning observed. For the GDL hole MEAs, it was discovered that smaller holes were more impactful on membrane durability than larger holes. Among the three selected hole sizes (2.0, 0.5, and 0.2 mm2), through-plane membrane cracks were only observed under the smallest holes, both at the hole center and edge, which are the two stress concentration locations. On the CL surface, cracks were observed at the GDL hole center as a crack network, and along the hole edge, as indicated in the figure. Although the GDL holes are expected to mainly alter mechanical membrane degradation, it was discovered that MEAs with through-plane membrane cracks also had higher membrane thinning rate compared to the baseline. However, the non-uniformity MEAs without through-plane membrane cracks had similar membrane thinning rate as the baseline test. Therefore, the through-plane membrane cracks likely elevated chemical stressors as well; hypothetically, through increased gas crossover. The AST results suggest that GDL holes can be harmful to membrane chemo-mechanical degradation and the level of severity depends on their size and location. Keywords: fuel cell; membrane durability; gas diffusion layer defect; mechanical degradation; chemical degradation; X-ray computed tomography Acknowledgements: This research was supported by the Natural Sciences and Engineering Research Council of Canada, Canada Foundation for Innovation, British Columbia Knowledge Development Fund, Western Economic Diversification Canada, Ballard Power Systems, and W.L. Gore & Associates. This research was undertaken, in part, thanks to funding from the Canada Research Chairs program.

Simulation of Proton Exchange Membrane Durability Under Fuel Cell Vehicle Operation – a Fundamental Study

Proton exchange membrane fuel cells (PEMFCs) have been proven to be a promising candidate to replace combustion engines due to their zero-carbon emission and high power densities. Despite the recent success in PEMFC commercialization, a number of challenges such as high cost and difficulty in lifetime estimation still hinder their further development. PEMFC durability tests require a long time to complete; therefore, durability predicting models are increasingly important as a supporting tool for further development and implementation.Fuel cell membranes undergo a variety of dynamic conditions during regular operation such as varying temperature, humidity, current density, and cell potential. The cyclic variations of humidity and temperature (hygrothermal variations) during dynamic operation lead to swelling and contraction of the membrane. The fluctuating stress caused by the continuous expansion and contraction of the membrane when confined within the cell leads to mechanical membrane degradation. The recurring swelling and contraction of the membrane which stem from water content changes in the membrane cause fatigue and creep and ultimately the formation of pinholes, cracks, and tears [1-2].Chemical membrane degradation occurs when radicals such as hydroxyl and hydroperoxyl are formed and attack the membrane and is escalated by high operating cell potentials. Chemical degradation results in decay in the ionomer chemical structure, membrane thinning, increased gas crossover, and potential electrode shorting [3]. The outcomes of such degradation are aggravated in the presence of mechanical degradation [4]. Hence, the study of combined chemo-mechanical membrane degradation is crucial for overall fuel cell membrane durability [5].The objective of the present work is to establish a predictive membrane lifetime simulation tool designed to represent chemo-mechanical membrane degradation under various operating conditions for automotive fuel cell applications. To this end, a statistical model is developed based on the membrane fibrillar morphology presented by El Hannach et al. [6-7]. A network of fibre bundles is generated to represent the membrane structure where any bundle is assumed as the primary building block of the membrane [8-10]. Each bundle contains an aggregate of backbone chains with typical mechanical and chemical properties. Mechanical and chemical degradation rates are separately studied and coupled in the model. The thermally activated breaking rate of each fibre is calculated to evaluate the mechanical degradation rate at any given time. In order to calibrate the mechanical degradation rate in the model, the mechanical degradation of a reinforced membrane under cross-pressure accelerated mechanical stress tests ( p-AMST) [11] is investigated to obtain the membrane fatigue lifetime for a variety of cross pressures and temperatures. Then, the genetic algorithm is successfully applied to optimize the experimental parameters considering the least squares method. Furthermore, accelerated membrane durability tests (AMDT) carried out by Macauley et al. [12] are considered to calibrate the chemical degradation rate parameter in the model. Finally, the fully calibrated model is used to estimate the membrane lifetime under realistic fuel cell vehicle operating conditions (e.g. drive cycles).Fuel cell components experience different degradation mechanisms. In this regard, this modelling framework on the membrane lifetime can be used in conjunction with other methodologies on the cathode catalyst lifetime such as [13-14] to scrutinize the key factors and their impacts on fuel cell durability under similar operating conditions. Acknowledgements This research was supported by the Natural Sciences and Engineering Research Council of Canada, Canada Research Chairs, and Simon Fraser University Community Trust Endowment Fund.

Impact of Reinforced Polymer Electrolyte Membrane Scratch on Fuel Cell Durability Using 4D X-Ray Computed Tomography Technique

PEMFCs, or Polymer Electrolyte Membrane Fuel Cells, can be used in both stationary power and transportation applications and are promising for use in heavy duty electric vehicles due to their high energy density, ability to be refueled quickly, and extended range, which are key challenges for battery-powered vehicles [1]. Despite these advantages, there are still obstacles preventing the widespread commercialization of PEMFCs, one of which is production cost [2]. To reduce manufacturing costs, it is imperative to ensure that quality control rejects and scraps are minimized. Moreover, enhancing component integration defect detection would ensure the durability of the fuel cell and enhance its operational lifetime. However, robust quality control requires a thorough understanding of potential non-uniformities and their effects on fuel cell performance and operational degradation.Non-uniformities of the membrane electrolyte assembly (MEA) can result in durability issues by damaging the membrane and making it more vulnerable to mechanical and chemical stress during the operation [3]. Several studies have been done on cation contamination and membrane pinholes and their effect on fuel cell performance and durability [4,5] but little attention has been paid to other types of non-uniformities such as membrane scratches and foreign particles, which may also conceivably affect durability [6]. By implementing 4D in-situ X-ray computed tomography (XCT) [7,8], the current work aims to track the evolution of scratches that appear on a reinforced membrane surface during fabrication and its specific objective is to determine the impacts of membrane scratches on membrane durability in fuel cells.The study was conducted by using small-scale fuel cells with GORE-SELECT® membranes that were intentionally scratched with a razor blade, subjecting them to combined chemomechanical membrane accelerated stress test (AST), and monitoring the membrane degradation and evolution of the scratches using 4D-XCT throughout the AST. During the fabrication step, the depth of scratches was regulated by a weak bond between the reinforcement layer and the perfluorosulfonic acid (PFSA) layer, i.e., the scratches did not tear through the reinforcement. Furthermore, the scratches did not adversely impact the initial cell performance. However, during AST operation the evolution of the scratched region was affected by several factors, including the friction between the layers of the membrane electrode assembly, the width of the scratch (Figure 1), the presence of membrane debris, and the extent of membrane strain. Additionally, it was observed that changes in the quality of catalyst layer transfer onto the scratched region can alter the degradation pattern and potentially create a self-mitigating mechanism. These findings may be used to develop more optimized quality control measures for membrane scratches in fuel cell production. Acknowledgements This research was supported by the Natural Sciences and Engineering Research Council of Canada, Canada Foundation for Innovation, British Columbia Knowledge Development Fund, Western Economic Diversification Canada, Ballard Power Systems, and W.L. Gore & Associates. This research was undertaken, in part, thanks to funding from the Canada Research Chairs program. Keywords: fuel cell; membrane durability; X-ray computed tomography; membrane scratch; manufacturing References [1] Cullen DA, Neyerlin KC, Ahluwalia RK, Mukundan R, More KL, Borup RL, et al. New roads and challenges for fuel cells in heavy-duty transportation. Nat Energy 2021;6:462–74. https://doi.org/10.1038/s41560-021-00775-z.[2] Whiston MM, Azevedo IL, Litster S, Whitefoot KS, Samaras C, Whitacre JF. Expert assessments of the cost and expected future performance of proton exchange membrane fuel cells for vehicles. Proc Natl Acad Sci U S A 2019;116:4899–904.[3] De Bruijn FA, Dam VAT, Janssen GJM. Review: Durability and degradation issues of PEM fuel cell components. Fuel Cells 2008;8:3–22.[4] Tavassoli A, Lim C, Kolodziej J, Lauritzen M, Knights S, Wang GG, et al. Effect of catalyst layer defects on local membrane degradation in polymer electrolyte fuel cells. J Power Sources 2016;322:17–25.[5] Lü W, Liu Z, Wang C, Mao Z, Zhang M. The effects of pinholes on proton exchange membrane fuel cell performance. Int J Energy Res 2011;35:24–30.[6] Kundu S, Fowler MW, Simon LC, Grot S. Morphological features (defects) in fuel cell membrane electrode assemblies. J Power Sources 2006;157:650–6.[7] Ramani D, Singh Y, White RT, Wegener M, Orfino FP, Dutta M, et al. 4D in situ visualization of mechanical degradation evolution in reinforced fuel cell membranes. Int J Hydrogen Energy 2020;45:10089–103.[8] White RT, Eberhardt SH, Singh Y, Haddow T, Dutta M, Orfino FP, et al. Four-dimensional joint visualization of electrode degradation and liquid water distribution inside operating polymer electrolyte fuel cells. Sci Rep 2019;9:1–12. Figure 1