Dantherm Power (Denmark)

Quality control of membrane electrode assembly (MEA) components is critical for the durability and lifetime of fuel cells. Previous gas diffusion layer (GDL) research has shown that features such as microporous layer (MPL) cracks or substrate pores may contribute to buckling-driven cracks in the membrane1,2. Our group recently reported a methodology for controlled implementation of GDL holes to isolate and determine their express impact on membrane durability3, which revealed that through-plane catalyst-coated membrane (CCM) cracks are likely to develop at small GDL holes located in regions under high compression, due to maximum stress concentration.The objective of the present work is to evaluate the systematic interactions between the GDL structure and chemo-mechanical membrane durability in fuel cells, considering a broader range of GDL materials with variations in physical properties and surface structure and their compatibility with thin, mechanically reinforced membranes. An in-situ 4D visualization technique by X-ray computed tomography (XCT) was chosen for the study, and the GDL samples were visualized using an XCT-compliant small-scale fuel cell, as was previously shown4. The MEAs comprised of GORE-SELECT® mechanically reinforced membrane, Pt/C catalyst layers, and GDLs with selected variations in substrate architecture (hydroentangled, dry-laid (Freudenberg) and wet-laid (AvCarb®) non-woven carbon papers), MPL thickness, and artificial hole presence. Based on previous work3, a 0.2 mm2 artificial through-thickness GDL hole was implemented within the fuel cell active area and the XCT field of view on the cathode GDL. All MEAs, with and without GDL holes, were tested under a custom-developed chemo-mechanical accelerated stress test protocol with an inclination towards mechanical stressors. Periodic identical location in-situ imaging was performed to track the degradation phenomena. The XCT images indicated significant uniform membrane thinning and minor GDL impingement in the defect-free baseline wet-laid GDL MEA. However, when tested with GDL holes, severe membrane buckling resulted in a substantial crack network formation in the CCM beneath the channels. The outcomes for the dry-laid and wet-laid substrates were similar in terms of test lifetimes, although certain differences were observed in the localized failure mechanisms. The extent of non-uniform global membrane thinning and fiber impingement increased drastically for the case of thin MPL. It is worth noting that exacerbated membrane thinning may be attributed to the membrane not being chemically stabilized. Furthermore, the relatively high surface roughness of the thin MPL enhanced the crack network formation in the catalyst layer, significantly reducing the membrane lifetime. Therefore, this study demonstrates that MPL roughness diminishes the lifespan of the MEA by promoting the creation of impingement sites and buckling, which leads to catalyst layer cracks and membrane thinning, culminating in membrane failure. A smooth MPL structure that is capable of distributing applied stress is required in order to ensure high membrane durability. Keywords: fuel cell, membrane durability, X-ray computed tomography, gas diffusion layer defect, quality control Acknowledgement This research was supported by the Natural Sciences and Engineering Research Council of Canada, Mitacs, Canada Foundation for Innovation, British Columbia Knowledge Development Fund, Pacific Economic Diversification Canada, and Ballard Power Systems. This research was undertaken, in part, thanks to funding from the Canada Research Chairs program.

Freeze-thaw (F-T) cycling in Proton Exchange Membrane Fuel Cells (PEMFCs) poses significant challenges to the long-term durability of their components [1,2]. Previous studies primarily relied on 2D imaging techniques to assess degradation effects. Recent advancements in X-ray tomography now enable high-resolution virtual 3D imaging, providing detailed volumetric insights and significantly improved structural information. This approach also preserves the cell’s operational integrity, avoiding artifacts introduced by disassembly and reassembly processes. This study leverages these advancements to investigate F-T cycling-induced degradation mechanisms in a small-scale fuel cell (active area: 0.39 cm²) using advanced in-situ X-ray Computed Tomography (XCT) imaging and electrochemical diagnostics.A custom-designed fuel cell fixture facilitated precise temperature control and real-time visualization of structural changes within the catalyst-coated membrane (CCM) [3]. The experimental design strategically applied localized stresses by controlling the initial water distribution within the membrane and catalyst layers, intensifying the effects of F-T cycling for focused investigation. XCT imaging revealed structural degradation after only 20 cycles (Figure 1), including delamination at the membrane-catalyst interface, crack formation in the catalyst layers (CLs) and membrane. Electrochemical analyses corroborated these findings, showing performance losses characterized by increased ohmic and mass transport resistances in polarization curves. Cyclic voltammetry highlighted significant reductions in the electrochemically active surface area (ECSA) of the catalyst, while impedance spectroscopy revealed substantial increases in high-frequency and catalyst layer resistance. These findings underscore the vulnerability of PEMFC components to F-T cycling and highlight the critical importance of advanced material design and mitigation strategies enhance durability of PEMFC’s components in harsh climates. Keywords: Freeze-Thaw Cycling – Proton Exchange Membrane Fuel Cells (PEMFCs) – X-ray Computed Tomography (XCT) – Membrane Degradation – Fuel Cell Durability Acknowledgements: This research is funded by the Natural Sciences and Engineering Research Council of Canada, Ballard Power Systems, Simon Fraser University, the Canada Foundation for Innovation, the British Columbia Knowledge Development Fund, the Canada Research Chairs Program, Mitacs and Pacific Economic Development Canada.

Under the background of the construction of the national unified electricity market, in view of the problem of reverse transmission fee recovery caused by the sharp increase in the volume of contract transfer in the inter-provincial multi-channel centralized bidding transactions, this study focuses on the characteristics of the "physical channel binding" mechanism and proposes two cost recovery mechanisms for reverse transmission fee collection and exemption. By constructing a node marginal electricity price model and conducting a comparative analysis with typical examples, the differences in market clearing efficiency and transmission channel utilization characteristics between the two mechanisms are revealed. Research shows that the reverse transmission rate mechanism screens out high-spread transactions through price signals, but it weakens market liquidity. The reverse exemption mechanism can increase the reverse trading volume of the Qingyu DC by 28.6%, but it requires the establishment of a cross-regional transmission fee balance account to achieve cost diversion, and at the same time leads to a 5% decrease in the channel utilization rate. The research conclusion provides a quantitative basis for the design of transmission pricing mechanisms and the formulation of policies for cross-regional consumption of new energy under the new power system.

The rate of gas transport through the PEMFC gas diffusion layers (GDL) is a function of GDL morphology, such as thickness, porosity, fibre diameters, tortuosity, etc.. Numerical methods can capture the intricacies of the GDL pore structure. However, the results obtained are specific to the analyzed structure and cannot be generalized to other GDLs due to inherent structural variations among different GDL types. By using a simplified representation of the complex pore structure, analytical methods offer a systematic approach to isolating the impact of each GDL structural property on GDL diffusivity. This understanding can be leveraged to adjust GDL design levers for an optimal GDL design. One of the key GDL structural properties is tortuosity which has a crucial impact on the transport properties of porous media. The literature [1,2,3], however, is unclear on how to relate tortuosity to gas diffusivity, and confusion arises when the two parameters, tortuosity, and tortuosity factor (defined as tortuosity squared) are used interchangeably. Besides tortuosity, varying cross-section areas along the path of gas transport affect the diffusivity of porous media. This parameter is referred to as the constrictivity factor [4].In this study, an analytical method is employed to demonstrate the relationship between diffusivity and tortuosity, resolving ambiguity on this matter. Additionally, a model is proposed to determine the constrictivity factor of GDLs. With the constrictivity factor established, the relative diffusivity of the GDL can be estimated through a closed-form analytical solution. The developed model is validated with data collected using our symmetrical modified Loschmidt cell. The gas diffusivity of several GDL samples has been measured, including TGP-060 with different PTFE contents (5, 10, and 20 wt%) which had relative diffusivities of 0.31±0.02, 0.29±0.02 and 0.26±0.01. In addition, experimental data available in the literature on TGP-060, TGP-090 and TGP-120 are also used for the validation of the developed model. The results show that the model estimates diffusivity of the sample with a maximum relative difference of 15%.[1] Flückiger, Reto, Stefan A. Freunberger, Denis Kramer, Alexander Wokaun, Günther G. Scherer, and Felix N. Büchi. "Anisotropic, effective diffusivity of porous gas diffusion layer materials for PEFC." Electrochimica Acta 54, no. 2 (2008): 551-559.[2] Inoue, Gen, Takashi Yoshimoto, Yosuke Matsukuma, and Masaki Minemoto. "Development of simulated gas diffusion layer of polymer electrolyte fuel cells and evaluation of its structure." Journal of Power Sources 175, no. 1 (2008): 145-158.[3] Tjaden, Bernhard, Dan JL Brett, and Paul R. Shearing. "Tortuosity in electrochemical devices: a review of calculation approaches." International Materials Reviews 63, no. 2 (2018): 47-67.[4] Van Brakel, Jaap, and P. M. Heertjes. "Analysis of diffusion in macroporous media in terms of a porosity, a tortuosity and a constrictivity factor." International Journal of Heat and Mass Transfer 17, no. 9 (1974): 1093-1103. Figure 1

A PEM fuel cell’s durability and lifetime are affected by various degradation phenomena, among which chemical degradation of PEM material exerts the most damage. Chemical degradation of PEM occurs when reactive radicals such as hydroxyl (·OH) and hydroperoxyl (·OOH) are generated from the decomposition of hydrogen peroxide. The radicals chemically attack the main and side chains of the perfluorosulfonic acid-based PEM and change its internal chemical structure. This leads to excessive membrane thinning and pinhole formation that causes higher gas crossover and electrode shorting inside the PEM fuel cell1. The generation of harmful radicals accelerates in the presence of Fenton’s metal, such as iron (Fe)2. Evaluation of PEM fuel cell chemical degradation durability is performed using long-term pure chemical accelerated stress test (AST) under high temperature (T), low relative humidity (RH), and open circuit voltage (OCV) conditions3. Physical characterization of a membrane sample used in a fuel cell can help to visualize and assess damage incurred during an AST. These results, however, fail to encompass the formation rate of radicals and intermediate degradation products generated during the AST3. To overcome these issues, computational fluid dynamics models are developed that simulate the evolution of degraded products and predict the lifetime of PEM fuel cells4,5.The present work aims to develop an in-situ one-dimensional (1-D) transient chemical degradation model that describes reaction-transport phenomena within the membrane electrode assembly (MEA) in the presence of Fe and Ce cations. This work considers mechanically reinforced GORE-SELECT® 15 µm baseline (MemA) and chemically and mechanically reinforced 12 µm (MemB-Ce) membranes. The developed in-situ model simulates pure chemical AST operating conditions with variable Fe ion loading and follows the computational algorithms originally presented by Wong and Kjeang4. The model successfully predicted that side chain scission is followed by main chain unzipping, as reported in the literature6. The evaluation of the change in ionomer structure by chemical degradation was done by computing the temporal concentration profile of intermediate degraded ionomer species, hydrogen peroxide, and membrane thickness reduction. The 1-D model also encapsulates the concentration profile of Fe2+ and Fe3+ ions across the PEM and predicts their temporal distribution throughout the simulated AST duration under OCV conditions. It was observed that the MemA thickness decreased rapidly in the presence of Fe ions, as shown in Figure 1. The computational parameters and results were calibrated and validated using in-house AST results for MEAs with embedded Fe metallic particles, which were shown to completely dissolve during conditioning and hence treated as uniformly distributed Fe cations with an initial concentration of 900 ppm at the beginning-of-life7. The model identified a limiting Fe ion concentration limit of 100 ppm that accentuates the chemical attack. Experimentally, a low Fe concentration of 10 ppm was determined in the baseline MemA, which also reduced the membrane thickness within 1125 h of operation, as shown in Figure 1. It is known that cerium (Ce) ions can scavenge harmful radicals and increase the lifetime of PEM fuel cells8. The model, therefore, simulates the effectiveness of Ce ions in the MemB-Ce membrane and the temporal distribution of Ce3+/Ce4+ ions and shows a lower rate of membrane thickness reduction, as shown in Figure 1. The modelling framework was, therefore, able to predict PEM fuel cell lifetime in conjunction with the transport behaviour of both harmful and beneficial cations as well as their interactions during the chemical degradation process at OCV conditions. Keywords: PEM fuel cell, fuel cell durability, chemical degradation model, in-situ modelling, iron, cerium 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. It was also undertaken in part thanks to funding from the Canada Research Chairs program. References J. Healy et al., Fuel Cells, 5, 302–308 (2005).S. Kundu, L. C. Simon, and M. W. Fowler, Polym. Degrad. Stab., 93, 214–224 (2008).Y. Singh, F. P. Orfino, M. Dutta, and E. Kjeang, J. Electrochem. Soc., 164, F1331–F1341 (2017).K. H. Wong and E. Kjeang, J. Electrochem. Soc., 161, F823–F832 (2014).R. B. Ferreira, D. S. Falcão, and A. M. F. R. Pinto, Int. J. Hydrogen Energy, 46, 1106–1120 (2021).L. Ghassemzadeh, K. D. Kreuer, J. Maier, and K. Müller, J. Phys. Chem. C, 114, 14635–14645 (2010).N. Kumar et al., ECS Meet. Abstr., MA2023-02, 1919–1919 (2023).S. M. Stewart, D. Spernjak, R. Borup, A. Datye, and F. Garzon, ECS Electrochem. Lett., 3, F19–F22 (2014). Figure 1

Abstract Metal binder jetting (MBJ) of AISI 904L super austenitic stainless steel makes it possible to produce complex components with a higher corrosion resistance compared to austenitic stainless steels such as AISI 304L and AISI 316L. The initial sintering trials resulted in a porous part with low corrosion resistance. As AISI 904L is a steel with austenitic phase throughout the entire sintering window, densification during sintering was inhibited which resulted in the reduced corrosion resistance due to open porosities. The trials were made with AISI 904L powder suited for MBJ but shaped through metal powder extrusion due to lack of printer availability. This paper will show how to enhance densification and utilize pickling in order to improve the corrosion resistance closer to the expected level comparable to cast and rolled material but with the shaping possibilities of MBJ.

Perfluorosulfonic acid (PFSA) polymer electrolytes are widely used in proton exchange membrane (PEM) fuel cell fabrication for the membrane separator and the electrode binder. The PEM serves to electrically insulate the cathode catalyst layer (CCL) from anode catalyst layer (ACL), provide proton conduction between both CCL and ACL, as well as prevent gas crossover. PFSA ionomers are also used in the CCL and ACL to mechanically bind the catalyst particles into thin-films, provide proton conduction between the PEM and catalyst surface, and produce a high proton reactant concentration at the oxygen reduction reaction catalyst. Despite their versatility to be used as a membrane and catalyst binder, the typical PFSA ionomers pose challenges due to the high oxygen transport resistance that is introduced by the thin ionomer films over the catalyst. In recent years, novel high oxygen permeability ionomers (HOPIs) have been developed as the successor to the traditional Nafion™ PFSA ionomers. Despite their remarkable results as a catalyst binder due to their increased oxygen transport rates, less is known regarding their degradation and functional lifetime. Although accelerated stress tests (ASTs) for platinum (Pt)/Pt-alloy catalysts, carbon supports, and membranes are well-established and commonly applied, there is no standard and easily implemented AST for electrode ionomers. One challenge is that membrane ASTs usually quantify the fluoride emission rate (FER) to assess chemical degradation, which is difficult to apply for electrode PFSA ionomer when also using a PFSA membrane because the FER is overwhelmed by membrane signal. In addition, changes in OCV and H2 crossover are not directly indicative of electrode ionomer degradation. Furthermore, concomitant degradation of the catalyst and support can interfere with interpreting electrode ionomer degradation. Here we present an effective and easily applied electrode ionomer chemical AST protocol that can be used to evaluate degradation in the functionality of the electrode ionomer. The approach borrows the chemical AST conditions of the chemical membrane AST’s open circuit voltage (OCV) hold and avoids excessive potential cycling to minimize catalyst and support degradation that will elicit changes in electrode properties separate from ionomer degradation. During the AST, we measure the cathode’s proton conduction resistance, oxygen permeability, and electrochemically surface area (ECSA) to evaluate the degradation of the ionomer’s functionality. Thus, this protocol can be used to assess if more complex and time consuming analyses of ionomer durability are needed as new chemistries emerge. Here we present results of this AST to both conventional PFSA ionomers and HOPIs.

The continuous elevation of wind power consumption pressure has proposed higher requirements for the technical means, which comprehensively support the wind power consumption. The power generation level of a wind power plant is measured through the utilization hours at present, but the factors influencing the utilization hours are scarcely analyzed and quantified. In order to accurately figure out the reasons for the different utilization hours of wind power plants located in the same area, the total power prediction, power plant data, standalone data, resources, etc. were summarized, and the contribution degrees of five dimensions—resources, equipment availability, AGC command balance degree, AGC command following performance, and power generation capacity—to the utilization hours were analyzed and quantified through the data fusion and feature extraction, in an effort to find the main factors influencing the utilization hours in different power plants. The customized measures were proposed according to the conclusions in order to increase the utilization hours for the power plants. The derived computing method was applied to the wind power plant data acquired by a company in a province, followed by the difference analysis of the utilization hours. It was found that in Mulan sectional area, the reason for partially low utilization hours in Jifeng and Xunfeng Wind Power Plants was resource factor, that for Daheishan and Songshan Wind Power Plants lied in equipment availability, and that for Jufeng Wind Power Plant was possibly equipment following performance or equipment power generation capacity. In addition, the AGC command balance degrees in all target power plants were at low levels.

The commercialization of fuel cell products for a variety of applications including forklifts, buses, cars and heavy duty trucks is well underway. Particularly in the heavy duty fuel cell market, recent studies suggest that in Europe, fuel cell electric buses (FCEB) total cost of ownership (TCO) will breakeven with battery electric buses (BEB) by 2023, and with internal combustion engine buses (ICEB) by 20241. For applications such as long-distance and heavy-duty transportation, the hydrogen route appears the decarbonisation option of choice, and can become cost competitive with internal combustion engines by 20302.Over the past 30 years, Ballard has developed a wide array of technology “building blocks” for Fuel Cell stacks components. The application requirements (duty cycle, speed, vehicle weight, lifetime and environmental exposure) will determine the key stack features and result in customization of components where economically viable. In contrast with fuel cell stacks developed for passenger cars, Fuel Cells for heavy duty vehicles are particularly challenged by high durability requirements3, with MEA attributes such as catalyst loading and peak efficiency point significantly affecting stack and fuel costs.Building on proven and demonstrated stack durability in the field of more than 35,000 hours in heavy duty vehicles4 Ballard’s MEA development activities draw from extensive field experience to support step changes in durability with each subsequent product iteration. The use of an accelerated testing and modeling approach developed and validated over numerous product iterations enables continuous cost decreases and gains in power density, operational robustness and reliability, with a calculated risk tolerance for new technology introduction.Those MEA durability prediction models along with a good understanding of failure mechanisms are a cornerstone to developing the next generation of Fuel Cells for heavy duty vehicles. Of particular importance is the use of the voltage degradation model to evaluate the time to reach the degradation target for heavy duty applications (USDOE Ultimate target of 10% degradation at 30,000 hours5). Simulation results as a function of the electrode composition show the relationship between cathode catalyst loading and lifetime, and assist in making electrode design and composition choices for a successfully durable product. A sharp increase in voltage loss is observed when local oxygen transport resistance becomes limiting once the cathode reaches low surface area. Maximizing beginning-of-life catalyst electrochemical surface area (ECSA) utilization in the electrode structure, as well as optimizing surface area retention, can have significant benefits for lifetime. A combination of design choices or processing parameters during catalyst layer fabrication can be effective ways to optimize the electrode6.The same voltage degradation model is used to demonstrate the relationship between lifetime and the peak operating current density of the product, which limits the stack design power density within the allocated voltage degradation constraints of heavy-duty vehicles.The simulation results demonstrate that the ideal Fuel Cell stack for heavy duty applications is the result of complex trade-offs between cost, stack design attributes (e.g. catalyst loading), active area sizing (peak efficiency point) and durability, with the ultimate goal to achieve an attractive TCO for wide acceptance of the technology. References Deloitte and Ballard. (2020). Fueling the Future of Mobility: Hydrogen and fuel cell solutions for transportation. Volume 1 [White paper]. Deloitte China. https://www2.deloitte.com/content/dam/Deloitte/cn/Documents/finance/deloitte-cn-fueling-the-future-of-mobility-en-200101.pdf McKinsey & Company and Hydrogen Council. (2020). Path to hydrogen competitiveness: A cost perspective. https://www.hydrogen.energy.gov/pdfs/19006_hydrogen_class8_long_haul_truck_targets.pdfMacauley, N., Lauritzen, M., Knights, S. and Kjeang, E., J. Electrochem. Soc., 165(10), F780 (2018).https://www.ballard.com/about-ballard/newsroom/news-releases/2020/01/27/ballard-powers-fuel-cell-electric-vehicles-for-unprecedented-30-million-kilometers-enough-to-circle-the-globe-750-timesUSDOE Hydrogen Class 8 Long Haul Truck Targets https://www.hydrogen.energy.gov/pdfs/19006_hydrogen_class8_long_haul_truck_targets.pdf M. Dutta, A. Young, V. Colbow, J. Bellerive, S. Knights, Examining Catalyst Layer Design Strategies for Improved Fuel Cell Performance and Durability, ECS PRiME 2020

Background: Prior studies have reported racial disparities in survival from out-of-hospital cardiac arrest (OHCA). However, these studies did not evaluate how emergency medical services (EMS) provider assessment of race impacts OHCA interventions and survival. Our objective was to evaluate racial disparities in OHCA airway management and patient outcomes in the multicenter Pragmatic Airway Resuscitation Trial (PART). Methods: We conducted a secondary analysis of adult OHCA patients enrolled in PART. Trial subjects were randomized to initial advanced airway management with laryngeal tube or endotracheal intubation. The primary independent variable was patient race (categorized by EMS as white, black, and other). We used general estimating equations (GEE) to examine the association of race (white or black) with airway attempt success, 72-hour survival, and survival to hospital discharge, adjusting for sex, age, witness status, bystander CPR, initial rhythm, arrest location, and randomization cluster. Results: Of 3002 patients, race was 1537 white, 860 black, and 605 other. Median times (min [interquartile range]) from dispatch to arrival (5.4 [2.8] vs. 5.0 [2.3]), arrival to CPR (2.2 [2.7] vs. 2.0 [2.7]), and arrival to airway attempt (12.2 [7.6] vs. 11.0 [7.4]) were longer for black compared to white patients, respectively. Black patients had lower unadjusted odds of shockable rhythms (OR 0.59; 95% CI 0.47, 0.74), bystander CPR (0.47; 0.39, 0.56), and survival to discharge (0.68; 0.50, 0.92) than white patients. After adjustment for confounders, black race was not associated with airway success (OR 1.13; 95% CI 0.9, 1.41), 72-hr survival (1.06; 0.81, 1.30), or survival to discharge (0.82; 0.57, 1.19). Conclusions: Although black patients had lower odds of shockable rhythms and bystander CPR, airway success and survival odds were similar to white patients. Further studies are needed to better understand disparities in survival from OHCA.