Strategies to Mitigate Degradation in Fuel Cell Materials

Abstract High-temperature proton exchange membrane fuel cells (HT-PEMFCs) could replace fossil fuel-based technologies for applications which cannot involve bulky/heavy cooling systems, such as aeronautics. However, severe materials degradations upon operation prevent performance retention for acceptable lifetimes. While others have already reported degradations in HT-PEMFC, post mortem characterizations of used HT-PEMFC membrane electrode assemblies (MEAs) remain scarce. Herein, HT-PEMFC performance degradation is studied by applying a startup/shutdown protocol to a short-stack operated at 160C; one MEA is characterized using complementary physicochemical/electrochemical techniques to identify/understand the degradation mechanisms and their origin. This start/stop operation mode (co-flow gas reactants) leads to substantial degradation inhomogeneity. For the anode, migration, coalescence, and detachment of Pt nanoparticles are witnessed induced by high-surface-area carbon support functionalization and corrosion. The anode electrochemical surface area (ECSA) remains constant at the i... Read More

Source

Electro-catalyst plays a central role in many clean energy technology applications including water electrolysis for green hydrogen generation, emission free fuel cells for transportation, electrochemical CO 2 reduction and combine heat and power generation. Electro-catalysts degrade via multiple mechanisms, depending on the exact operating conditions in its life cycles. In this presentation, we demonstrate the dependance of the electro-catalyst degradation in polymer electrolyte fuel cell (PEFC) on the specific paths that the fuel cell takes to age. Specifically, differently ordered aging protocols with the same total number of accelerated stress tests (ASTs) cycles ( i.e., 31,000 total cycles including 30,000 cycles of square-wave load/unload ASTs and 1000 cycles of triangular-wave carbon corrosion ASTs) were used to degrade membrane electrode assemblies (MEAs). At the end-of-life, performances were distinct, indicating that depending on the specific aging route taken, the fuel cell catalyst layer degrades differently after same number of total AST cycles. The load/unload aging pr... Read More

Source

Fuel cells hold immense promise as efficient and sustainable power sources for transportation and stationary applications. However, their operation can be severely impacted by air pollutants, particularly sulfur dioxide (SO 2 ) and nitrogen oxides (NOx). These pollutants can adsorb onto the platinum catalyst, leading to a decrease in fuel cell performance and durability. In this study, we investigate the impact of SO 2 and NO 2 on PEM fuel cell performance and durability. The contamination tests were carried out at a constant current density of 0.5 A.cm 2 , and they consisted of four steps: a pre-poisoning step to evaluate initial performance (15-16 h), poisoning step (50 h), self-recovery in a pure air stream (20-21 h) and a driven CV-induced recovery. Electrochemical characterizations were carried out at the end of each step (Polarization curve, Electrochemical Impedance Spectroscopy, Cyclic Voltammetry and H 2 Crossover). Our initial investigation involved contaminating a single fuel cell with a low concentration of 0.1 ppm of sulfur dioxide (SO 2 ). Remarkably, this resulted in ... Read More

Source

In order to enhance the durability of fuel cell systems in fuel cell hybrid electric vehicles (FCHEVs), researchers have been dedicated to studying the degradation monitoring models of fuel cells under driving conditions. To predict the actual degradation factors and lifespan of fuel cell systems, a semi-empirical and semi-physical degradation model suitable for automotive was proposed and developed. This degradation model is based on reference degradation rates obtained from experiments under known conditions, which are then adjusted using coefficients based on the electrochemical model. By integrating the degradation model into the vehicle simulation model of FCHEVs, the impact of different fuel cell sizes and dynamic limitations on the efficiency and durability of FCHEVs was analyzed. The results indicate that increasing the fuel cell stack power improves durability while reducing hydrogen consumption, but this effect plateaus after a certain point. Increasing the dynamic limitations of the fuel cell leads to higher hydrogen consumption but also improves durability. When consideri... Read More

Source

Abstract The lifetime of hydroxyl radicals ( OH) in the fuel cell catalyst layer remains uncertain, which hampers the comprehension of radicalinduced degradation mechanisms and the development of longevity strategies for protonexchange membrane fuel cells (PEMFCs). In this study, we have precisely determined that the lifetime of OH radicals can extend up to several seconds in realistic fuel cell catalyst layers. This finding reveals that OH radicals are capable of carrying out longrange attacks spanning at least a few centimeters during PEMFCs operation. Such insights hold great potential for enhancing our understanding of radicalmediated fuel cell degradation processes and promoting the development of durable fuel cell devices.

Source

Proton exchange membrane fuel cells (PEMFCs) have the potential to tackle major challenges associated with fossil fuel-sourced energy consumption. Nafion, a perfluorosulfonic acid (PFSA) membrane that has high proton conductivity and good chemical stability, is a standard proton exchange membrane (PEM) used in PEMFCs. However, PEM degradation is one of the significant issues in the long-term operation of PEMFCs. Membrane degradation can lead to a decrease in the performance and the lifespan of PEMFCs. The membrane can degrade through chemical, mechanical, and thermal pathways. This paper reviews the different causes of all three routes of PFSA degradation, underlying mechanisms, their effects, and mitigation strategies. A better understanding of different degradation pathways and mechanisms is valuable in producing robust fuel cell membranes. Hence, the progress in membrane fabrication for PEMFC application is also explored and summarized.

Source

Abstract A critical challenge to the commercialization of clean and high-efficiency solid oxide fuel cell (SOFC) technology is the insufficient stack lifespan caused by a variety of degradation mechanisms, which are associated with cell components and chemical feedstocks. Cell components related degradation refers to thermal/chemical/electrochemical deterioration of cell materials under operating conditions, whereas the latter regards impurities in feedstocks of oxidant (air) and reductant (fuel). This article provides a thermodynamic perspective on the understanding of the impurities-induced degradation mechanisms in SOFCs. The discussion focuses on using thermodynamic analysis to elucidate poisoning mechanisms in cathodes by impurity species such as Cr, CO 2 , H 2 O, and SO 2 and in the anode by species such as S (or H 2 S), SiO 2 , and P 2 (or PH 3 ). The author hopes the presented fundamental insights can provide a theoretical foundation for searching for better technical solutions to address the critical degradation challenges.

Source

Cell deterioration over time is one of the most perplexing obstacles to long-term fuel cell performance. In this study, we employed both in situ and ex situ analytical approaches to investigate the deterioration mechanisms of state-of-the-art AEMFCs.

Source

Due to its zero emissions, high efficiency and low noise, proton exchange membrane fuel cell (PEMFC) is full of potential for the application of vehicle power source. Nonetheless, its lifespan and durability remain multiple obstacles to be solved before widespread commercialization. Frequent exposure to non-rated operating conditions could considerably accelerate the degradation of the PEMFC in various forms, thus reducing its durability. This paper first analyses degradation mechanisms of PEMFCs under typical automotive operating conditions, including idling, startup-shutdown, dynamic loads, and cold start. The corresponding accelerated stress testing methods are also discussed. Then, as the impurities existed in the reaction gas source and generated from the degradation of the PEMFC itself may occur under all automotive conditions, the degradation mechanisms caused by impurity contamination are classified and reviewed in detail. After that, the techniques proposed by researchers to enhance the durability of PEMFCs are presented from four aspects: MEA materials, bipolar plates and f... Read More

Source

<title>Abstract</title> Polymer electrolyte membrane fuel cells (PEMFCs) have faced challenges in achieve their lifespan goals due to the degradation of the membrane electrode assembly (MEA) during long-term operation. To enhance the durability of PEMFCs, it is necessary to research materials that can improve the durability of the membrane and electrodes, as well as to study operating conditions that can reduce degradation. This paper investigated methods to mitigate the membrane degradation of electrochemically degraded MEAs by controlling humidity and temperature among the operating conditions. MEA was degraded electrochemically by conducting open circuit voltage (OCV) holding, and then the degradation rate according to temperature and humidity changes was observed through fluoride emission rate (FER) change. In a degraded MEA, it is shown that increasing cell humidity accelerates membrane degradation. According to linear sweep voltammetry (LSV) results, this was confirmed to be due to the increase in hydrogen permeability caused by the higher humidity. The decrease in temperature ... Read More

Source

<title>Abstract</title> The durability of polymer electrolyte fuel cells (PEFCs) in fuel cell electric vehicles (FCEVs) is important for the shift from passenger cars to heavy-duty vehicles. The components of a PEFC, namely the proton exchange membrane (PEM), catalyst layer (CL), and gas diffusion layer (GDL), contribute to the degradation of the fuel cell performance. These degradation studies were conducted independently and focused on PEMs and CLs. The degraded fuel cell stack in FCEVs is completely replaced. Therefore, it is necessary to counteract rapid material degradation in PEFCs. In this paper, we propose a method for simultaneously evaluating the degradation rates of these components by combining electrochemical characterization with operando synchrotron X-ray radiography. The open-circuit voltage, electrochemically active surface area, and water saturation were used as the degradation indicators for the PEMs, CLs, and GDLs, respectively. The results of two accelerated stress tests (loading and start-stop cycles) showed that the increase in water saturation owing to the los... Read More

Source

Fuel cells are one of the prioritized energy conversion technologies with highly focused research and development. For the whole fuel cell commercial realization on the market, fuel cells must be very affordable. This realization calls for critical developments in addressing the technical hindrance such as the overall fuel cell cost, electrocatalysts stability, and durability. A step towards fuel cell commercialization means well-defined architectural electrocatalysts designs that fully enhance the oxygen reduction reaction and fuel oxidation reaction. The currently pursued electrocatalyst has drawbacks. These include poisoning from methanol and ethanol cross-over, sluggish anodic and cathodic kinetics, air, fuel management, stability, and durability management. This chapter aims to elucidate how the mentioned challenges affect the electrocatalytic activity of the electrocatalysts and expound on some approaches to mitigate the challenges, enhancing adaptability as fuel cells electrocatalysts.

Source

On their way to their commercialisation, Fuel Cell Heavy Duty Trucks stakeholders need to demonstrate their cost effectiveness against conventional Diesel Trucks. Beyond the economies of scale of all relevant components that are employed in a Fuel Cell Electric Heavy Duty Truck, the durability of the Fuel Cell System and notably that of the Fuel Cell Stack plays an important role in the determination of a competitive cost of ownership. A key factor for durability improvement is the understanding of the degradation mechanisms and their mitigation. Degradation, however, can be very application specific, that is, different degradation mechanisms may be prevalent in heavy duty truck applications compared to passenger cars or stationary use. This is well known to research and industry. The European research project IMMORTAL is exactly aiming at exploring these mechanisms and their mitigation specifically for heavy duty truck application and developing and MEA that meets heavy duty requirements. Within this context, FPT Industrial, a brand of the Iveco Group, assists in defining the specif... Read More

Source

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 (... Read More

Source

Professor Anil Virkar has been a pioneer in the development and characterization of high-performance anode-supported solid oxide fuel cells, and in understanding degradation processes in such cells operated in electrolysis mode. This talk reviews methods for improving anode-supported cells, particularly for yielding high performance at reduced operating temperature. The understanding of degradation mechanisms occurring during solid oxide electrolysis cell operation will be discussed.

Source

This study deals with Polymer Electrolyte Fuel Cells (PEFC), which are used in automobiles and household fuel cells. Currently, there are two main challenges for the practical application of PEFCs: durability and cost reduction. The target value for durability is required to be 40,000 hours or more. However, the current durability is about 10,000 hours. Therefore, there is an urgent need to investigate the causes of deterioration and to take countermeasures. One of the causes of degradation is chemical degradation of the polymer electrolyte membrane. When the byproduct hydrogen peroxide encounters impurities such as iron ions, hydroxyl radicals are generated, which attack and degrade the polymer electrolyte membrane. To prevent this degradation, a substance that inactivates hydroxy radicals (radical scavengers) has been featured. Radical scavengers have been added to the polymer electrolyte membranes to prevent this degradation and are now being used in practical applications. One of the most useful radical scavengers is Ce ion. However, it has been observed experimentally that Ce io... Read More

Source

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 (&lt; 100 W) 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... Read More

Source

Predicting degradation of polymer electrolyte membrane fuel cells (PEMFCs) is an important issue from the viewpoint of durability and cost. In fact, in technical roadmaps regarding fuel cell of each country, high targets of durability and performance are set for transport applications especially for heavy duty vehicles. One of important degradation process takes place in catalyst layer. PEMFC catalysts are typically platinum or platinum alloys and consist of nanoparticles to increase the electrochemically active surface area (ECSA). However, these particles are not stable in dynamic operating conditions of the transport applications. A typical degradation mechanism of the catalyst is the electrochemical Ostwald ripening mechanism, and it is known that the platinum particle size distribution shifts to larger particle diameter, resulting in lower ECSA and lower performance. Therefore, predicting platinum catalyst degradation is important to enhance durability of the products. Various numerical models for catalyst degradation of PEMFC have been proposed and used to explore degradation m... Read More

Source

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]. Se... Read More

Source

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... Read More

Source

A central target of fuel cell technology development at present is maintenance of high performance and performance stability of the cell over significantly extended durations. Accordingly, modes of performance loss observed frequently for fuel cell electrodes, including electrodissolution, agglomeration, and catalyst surface passivation, are discussed here followed by descriptions of possible means of protection against each form of catalyst loss or deactivation, to secure extended cell operation at stable performance. In this discussion, the role of catalyst surface layers is of particular interest. Adverse and beneficial functions of such layers seem to come intertwined almost as a rule, and therefore, the idea of adding a surface overlayer to protect electrocatalysts against various modes of loss and deactivation is intriguing. Along these lines, several recent reports have described "catalyst capping" as a potential approach for the reduction of the rate of catalyst performance loss while maintaining the same activity as that of the noncapped catalyst at beginning of life ( BOL )... Read More

Source

Fuel cells are anticipated to play an important role in the future clean energy economy as versatile energy conversion devices across many applications and sectors, including transportation powertrains, stationary power systems, and specialty applications. While fuel cells for these diverse applications have some common foundations, the systems for each application have different requirements and priorities, which call for different system designs and technologies to meet them. The development of advanced, application-relevant materials and electrocatalysts is essential to overcoming the technical challenges that remain to bring fuel cells into widespread adoption and realization of their potential. This chapter discusses how application requirements and system-level considerations create constraints on fuel cell materials and electrocatalysts, with the goal of informing more strategic and impactful research and development efforts.

Source

Due to the non-renewable nature and pollution associated with fossil fuels, there is widespread research into alternative energy sources. As a novel energy device, a proton exchange membrane fuel cell (PEMFC) is considered a promising candidate for transportation due to its advantages, including zero carbon emissions, low noise, and high energy density. However, the commercialization of fuel cells faces a significant challenge related to aging and performance degradation during operation. In order to comprehensively address the issue of fuel cell aging and performance decline, this paper provides a detailed review of aging mechanisms and influencing factors from the perspectives of both the PEMFC system and the stack. On this basis, this paper offers targeted solutions to degradation issues stemming from various aging factors and presents research on aging prediction methods to proactively mitigate aging-related problems. Furthermore, to enhance prediction accuracy, this paper categorizes and analyzes the degradation index and accuracy evaluation criteria commonly employed in the exi... Read More

Source

Abstract Polymer electrolyte fuel cells (PEFCs), considered green devices, use hydrogen and oxygen as reactants in electrochemical processes to produce electricity, water, and heat as by-products. The use of this technology in the automotive industry and power generation has led to a detailed study of its operating principle to make it cost-effective. Polymer electrolyte fuel cells as innovative technology has promoted research to improve its performance. For this reason, a review of the accelerated degradation methods for the membrane, the catalyst layer, the gas diffusion layer, and finally, the bipolar plates are presented. In this work, it also been found that accelerated stress test has already been standardized for cell structure in general however and on the other side there is a little research on degradation methods for bipolar plates. Finally, a brief review of the mitigation strategies has been carried out, given that with the compilation of accelerated aging in the fuel cell structures, it has been observed that the research is focused on improving materials for the use i... Read More

Source

The paper considers the main aspects that cause mechanical and chemical degradation of a solid polymer fuel cell during its operation.For each of these reasons, the currently existing approaches to its solution are indicated.

Source

This paper focuses on the main chemical, electrochemical, and mechanical degradation mechanisms and poisoning effects that influence the life-time, the performance, and the functionality of PEM (polymer electrolyte membrane) fuel cell stack components reversibly and irreversibly. The underlying causes are explained, possible influencing factors are listed, and the effects of degradation on fuel cell operation and state of health are described. Based on this, further consequences as well as mitigation strategies are presented. The summary gives an overview of the affected causes of voltage decay, the influence of operating conditions, strategies, and events on each specific degradation mechanism, and additionally the influence of initial degradation on any further degradation.

Source

The operation of a fuel cell poses significant problems related to local current density and the failure rate of components. The issue results from high flow resistance and stresses that guarantee the tightness of the stack. Low flow resistance allows the stack to be used in Hybrid Energy Storage. This study shows that the selection of the best variant of the channel shape in a fuel cell should be based on more than just observing electrochemical performance. Increasing the current density flux can lead to faster component degradation. Older material degradation models based on the strain tensor will only accurately identify some risks. Thanks to the use of Perzyna's viscoplastic model, it was possible to protect the fuel cell from premature failure. Earlier studies did not indicate how the changes in the shape introduced, improving the electrochemical properties, impacted the component's service life during cyclic loads.

Source

The performance degradation mechanisms, mitigation strategies and durability protocols of polybenzimidazole-based polymer electrolyte membrane fuel cells are fully reviewed.

Source

Fuel gas utilization and water management are particularly challenging integrated engineering problems in hydrogenoxygen proton exchange membrane fuel cell (H 2 /O 2 PEMFC) systems. Herein, a standardized process is adopted to evaluate the performance and investigate the degradation mechanisms of a PEMFC with dual exhaust gas recirculation. The purpose of incorporating recirculation subsystems in the fuel cell is to achieve a high fuel gas utilization rate and realize effective water management inside the stack, which consists of 3Dprinted ejectors and a customized recirculation pump. Evaluation of the electrochemical performance degradation and morphological characterization of the fuel cells under different operating strategies are performed after 50 h durability experiments. At a current density of 400 mA cm 2 , the performance degradation rates of the stack decrease from 16.50% to 7.49% and 0.71% in the ejector and recirculation pump operation strategies, respectively. The results show that using exhaust gas recirculation devices (ejector/pump) in the fuel cell stack can help ... Read More

Source

Durability is one of the biggest challenges for automotive applications powered by proton-exchange membrane (PEM) fuel cells. Under automotive driving cycles, the fuel cells may experience frequent startupshutdown, freezethaw, dynamic loading, and idling conditions, which can shorten the lifetime of fuel cell vehicles. Therefore it is of significant importance to understand the fundamental aging phenomena under typical driving conditions in different fuel cell components. In this chapter, the aging phenomena in major PEM fuel cell components, such as membranes, catalyst layers, gas diffusion layers, and bipolar plates, are systematically examined, and the causes of the component degradation are analyzed. The aging phenomena and the corresponding causes are investigated by various experimental methods, which can be categorized into two types: steady-state durability test and accelerated stress test (AST). The steady-state durability test can directly determine the lifetime of fuel cells when they are used to generate constant power in a hybrid fuel cellbattery vehicle. However, ste... Read More

Source

Despite impressive developments in the technology of proton-exchange membrane fuel cells (PEMFCs), large-scale commercialization still faces issues of low stability and durability that continue to be adversely affected by impurities in the PEMFC system. This article provides a thorough discussion of the impurity and contamination issues that have plagued PEMFC performance. After a brief introduction to the operational principles of the PEMFC, the common sources of impurities in PEMFC systems are discussed, including fuel-side impurities (COx, H2S, and NH3), air-side impurities (NOx, SOx, and COx), and impurities coming from the system components themselves. The effect of contamination and the mechanisms of these impurities on fuel cell operation and performance are presented, followed by a detailed discussion of current strategies for mitigating contamination. Finally, suggestions are provided for future work in PEMFC contamination research.

Source

The durability and degradation issues of Polymer Electrolyte Membrane Fuel Cells (PEMFCs) utilized in high-humidity environments and small stack sizes are investigated in this study. To address the lack of uniformity in operation and the resulting degradation, a method for improving the uniformity of current density distribution and reducing degradation in PEMFCs is proposed. This is achieved by periodically controlling the flow direction using a reverse-flow configuration. The proposed method resulted in a delay of degradation by approximately 7% based on the end of degradation experiment. Furthermore, the uniformity of current density distribution and voltage differences between cells in the stack were improved. The proposed method exhibits potential for enhancing the durability and performance of PEMFCs in high-humidity environments and small stack sizes, thereby mitigating carbon or Pt degradation, particularly in applications such as micro mobilities.

Source

As energy demand increases, global warming progresses, and energy resources are scarce in the future, expectations for fuel cells, which generate electricity through a chemical reaction between hydrogen and oxygen, are rising. There are various types of fuel cells, which are classified according to the electrolyte. This study deals with polymer electrolyte fuel cells (PEFCs), which are used in automobiles and household fuel cells. Currently, there are two main challenges for the practical application of PEFCs: durability and cost reduction. The target value for durability is required to be 40,000 h or more. However, the current durability is about 10,000 h, so an investigation into the causes of deterioration and countermeasures are urgently needed. One of the causes of degradation is the chemical deterioration of polymeric membranes. When the by-product hydrogen peroxide comes into contact with impurities such as iron ions, hydroxyl radicals (OH) are generated, which attack and decompose the polymer membrane. In order to suppress this degradation, research have been conducted to ad... Read More

Source

Chemical degradation and mechanical degradation are the major challenges for heavy-duty vehicle fuel cell commercialization. Perfluorinated sulfonic acid is the benchmark material that has high proton conductivity and robust mechanical properties. However, chemical degradation can occur through radical formation during the fuel cell operation. Chemical degradation can also have a synergetic effect with mechanical degradation. Recent studies have used cerium and manganese additives to suppress the radical formation or chemical degradation caused by radicals. The limitation of the metal and metal oxide additives was the migration and agglomeration of the additives. Both migration and clustering can lead to changes in membrane morphology, resulting in a loss in proton conductivity. Our group has previously reported that immobilization of heteropoly acid to a fluoroelastomer can be used to both enhance proton conductivity and chemical degradation. The durability test has shown that the chemical durability was significantly enhanced, but the mechanical durability remained the challenge. I... Read More

Source

Fuel cells are promising clean power sources which use hydrogen and oxygen to generate electricity. However, the limited durability that is decided by various degradation phenomena remains one of the main barriers hindering their commercialization. Fuel cell deterioration modeling contributes to model and reproducing fuel cell deterioration behaviors, thus serving as a key step to decreasing fuel cell system deterioration. Fuel cell deterioration behavior is characterized by two main features, namely, load-dependent and stack-to-stack deterioration heterogeneity. A Gamma process with random effect-based deterioration model is used to account for the above deterioration features of fuel cells. Different types of random effects are introduced to the studied Gamma process on its scale parameter, taken as a random variable following a gamma law. Fuel cell degradation trajectories are studied by the developed deterioration models using the Monte Carlo simulation method. The lifetime distributions of the proposed models are analyzed for investigating their deterioration behavior.

Source

In the recent years, the use of fuel cells for the propulsion of passenger vehicles and heavy-duty vehicles has gained renewed interest as alternative to internal combustion engine-powered vehicles. Particularly for the latter, the long-term durability of proton-exchange-membrane fuel cells (PEMFCs) is still a concern, which in part is governed by the catalyst layer durability during system operating conditions. 1 During the operation of a PEM fuel cell system, certain transient conditions can occur that can lead to rapid degradation of the catalyst layers. On one hand, the widely studied start-up/shut-down (SUSD) phenomenon leads to significant degradation of the cathode catalyst layer due to the exposure of the cathode electrode to high potentials (&gt;&gt;1.0 V vs the reversible hydrogen electrode potential (V RHE )) that results from a H 2 /air-front passing through the anode flow field. 2 On the other hand, an intermittent under-supply of hydrogen to one or several cells of a PEMFC stack can lead to a so-called cell-reversal (CR) event, resulting in the oxidation of the carbon s... Read More

Source

Prognosis and Health Management is a powerful approach in the quest to improve fuel cell durability. Prognosis is applied to quantify and predict the fuel cell state of health. By assessing the state of health, fuel cell operating conditions can be adapted to reduce its degradation rate. The objective of this paper is to present a fuel cell prognosis method. An empirical model separating membrane and catalyst degradation is adopted. The model coefficients are estimated using a particle filter. The prediction results are encouraging as the fuel cell voltage can be accurately estimated and predicted. The prognosis method presented in this paper is trained and validated using proton exchange membrane fuel cell stack data, going through a dynamic load profile. This novel experimental data has been generated at Sintef Laboratory, on an automotive fuel cell short stack provided by Symbio.

Source

Abstract Fuel cell electric vehicles (FCEVs), which use polymer electrolyte membrane fuel cells (PEMFCs), provide a prospect to add to a future of harmfulemissionfree mobility. However, an indepth understanding of degradation mechanisms and contributions to performance losses is needed to commercialize FCEVs further. Most previous PEMFC degradation research has focused on global indicators of the cell condition. Still, failure occurs typically due to inhomogeneities in production or operation, leading to localized regions of high degradation rates. Despite simulations indicating that local degradation effects are significantly more pronounced at larger scales, experimental studies only exist for smallsized laboratory fuel cells so far. Here, we present the results of a comprehensive study of spatial distributions of essential PEMFC parameters using electrochemical impedance spectroscopy across the cell surface of automotivesize fuel cells with an active area of 285 cm 2 . In particular, the results reveal increasing mass transport problems with increasing distance from the air i... Read More

Source

The levelized cost of reversible fuel cells is used to identify benefits associated with oxygen use. For the same application, only three parameters influence the cost: roundtrip efficiency, total installation and operation/maintenance costs. The higher efficiency reversible solid oxide fuel cell is preferred. Volume considerations suggest oxygen use in heavy-duty proton exchange membrane fuel cells (PEMFCs). Oxygen differentially affects PEMFC degradation modes and limited data hamper the estimation of operation/maintenance costs. Comparative cost analyses and durability data are needed to ensure that the anticipated massive amount of oxygen produced by electrolysis, which is frequently vented, is not a lost opportunity.

Source

In the commercialization of the hydrogen fuel cell for the transportation sector, one of the main factors affecting the lifespan of the fuel cell is voltage reversal, especially when the anode of the fuel cell is subject to fuel starvation momentarily during the operation. In this article, mitigation methods for voltage reversal are summarized in three parts, namely, the catalyst approaches, the MEA design approaches, the stack and system strategies approaches, which include the application of a highly active oxygen evolution reaction (OER) catalyst or durable catalyst support in the anode, employing a protective layer for the catalyst layer or optimizing the formula of the catalyst layer or employing a durable GDL, or optimization of stack design or system operation strategies.

Source

Today the world is full of time-dependent phenomena in all fields: physics, chemistry, mechanics and many others. Time acts on the performance of any system whatever its nature is. When a system operates over time, aging becomes a real concern. Regarding fuel cells, several degradation phenomena can occur in a short or long term. Short-term phenomena are generally referred to as reversible degradations, these degradations are of the order of the microsecond and can go up to hours and sometimes to days, such as problems related to water management. The long term degradations are usually called irreversible degradations; it can be defined as aging. This phenomenon is of the order of a day and can increase up to months. In order to mitigate the impact of aging on the fuel cell system performance, good corrective actions must be taken. To do so, the performance prediction during the aging of the fuel cell system must be conducted. In this paper a verified and tested prognosis approach applicable to fuel cells is presented. The novelty in the approach used is linked to its modular structu... Read More

Source

In order to study the changing regularity of proton exchange membrane fuel cell (PEMFC) performance in the aging process under load cycling condition and improve the durability of fuel cell, the orthogonal experiment method was introduced. In this paper, three-factor and three-level orthogonal experiments were set up to study the influence of upper potential limit (UPL), lower potential limit (LPL) and period of the load cycle on the degradation rate of fuel cell. The test results show that under variable load cycling conditions, the fuel cell performance decays first fast and then slowly. The degradation rate after hundreds of hours of load cycling experiment is usually less than 50% of that of the fresh fuel cell. The dominant factor which effect the degradation mostly significantly changes during the whole aging process. According to the influence degree of three factors on performance degradation rate, the degradation process can be divided into three stages: the UPL dominating stage, the LPL dominating stage and the slow decay stage. In order to mitigate the performance degradat... Read More

Source

Various research are currently done about fuel cells. They can concern the application context, the fuel cell technology by itself or the socio-economic bolts. This paper deals with fuel cells stack testing and especially the accelerated stress testing. Long and expensive ageing tests are performed to study the behavior of the fuel cell with the aim of making it as robust as possible versus permanent degradation over time. Accelerated stress tests should provide results faster as classical ageing tests, thus inducing cost reduction. This paper reviews fuel cell component degradation, including degradation mechanisms, and the accelerated stress tests dedicated to all the constituting components (catalyst layer, membrane, gas diffusion layer and bipolar plates). Obviously, the harmonized accelerated stress tests given by the Department of Energy (DoE) are presented but all other recent accelerated test protocols proposed in the literature are also reviewed. In addition, several tables are given to detail operating conditions, specimen, characterization planning and a degradation rate t... Read More

Source

Abstract Fuel cells for mobile applications obtain their oxygen from the ambient air in road traffic. This air has contaminations of various impurities that can have negative effects on the lifetime of fuel cell systems in vehicles. The identified most relevant contaminants are toluene, nitrogen dioxide, ammonia, and sulfur dioxide. A modified test bench enables different dosages of the abovementioned pollutant gas concentrations on the cathode side. We examined influences both in static cycles for quasisteady states and in dynamic cycles for rapid load changes to examine reversible and irreversible degradation effects. We showed that the harmful cathode gases examined could lead to a shortening of the service life of fuel cells. Whereas this is well known for higher concentrations of pollutants, this contribution provides data in the subppm range including the effects of gas mixtures for which literature data is still limited. Additionally, a physical fuel cell model is developed to analyze the effects of various contaminants. The overall intention is to determine acceptable ... Read More

Source

Abstract Voltage degradation is the main parameter that determines the effective usable life of a fuel cell, here the influence of Pt/C% and relative humidity (RH%) on the voltage decay rate of a fuel cell is experimentally evaluated and reported. This study implements a stress test with frequent interrupts of purging for determining the durability of the fuel cells. In the course of the 1456 h stress test for each membrane electrode assembly (MEA), the polarization curve and electrochemical impedance spectroscopy (EIS) were measured. The experimental results make it evident that the lowest voltage degradation was 6 V/h for MEA with 40% Pt/C tested under 70% RH while the highest was 183 V/h recorded for MEA with 20% Pt/C tested under 90% RH. From EIS results, the ohmic resistance increased for all the tested MEAs, which is also reflected in the performance degradation. Field emission scanning electron microscopy images also indicate the delamination of MEA layers which in turn increases the electron transfer resistance. So, the decisive factors for the fuel cell performance degrada... Read More

Source

Proton exchange membrane fuel cell (PEMFC) is considered as a very promising power conversion device for automobiles. Despite many significant technological and fundamental advances having been made in the past decades, obstacles limiting the commercialization of automotive PEMFCs remain in the aspect of lifespan, which is mainly affected by several aspects such as various operating conditions. Especially, the start-stop process is an inevitable and frequent operating condition for automotive PEMFCs, which makes it of great significance to mitigate the PEMFC performance degradation under an operating condition. Based on the analysis of the PEMFC degradation mechanism during the start-stop process, three main entry points for the current start-stop decay mitigation strategies are summarized: disrupting the conditions for carbon carrier corrosion, reducing the existence time of hydrogen-air boundary inside the anode, and limiting the potential of the cathode catalyst layer. This paper presents a comprehensive review of control strategies to mitigate PEMFC start-stop performance degrada... Read More

Source

The frequent off design operation of fuel cell is the main reason for the reduction of system life. From the physical point of view, the transient of current load under variable operating conditions will cause frequent changes in reaction gas pressure, pressure, temperature and humidity. This leads to irreversible damage to the material itself. From the chemical aspect, it will cause voltage change, lead to irreversible damage of the material itself, and lead to poor battery durability. The study on the attenuation mechanism of PEMFC membrane electrode under different working conditions lays a foundation for the subsequent research of attenuation machine, and is of great significance to promote the commercialization of fuel cell.

Source

Due to the high gravimetric energy density of hydrogen, the focus of implementation of polymer electrolyte fuel cells (PEFCs) has shifted from light duty passenger vehicles to heavy duty vehicles such as buses, trucks, locomotives and marine vessels 1 .A mechanistic understanding of degradation is therefore necessary to improve durability and efficiency.During start-up and shutdown (SUSD) of PEFC systems, the catalyst (Pt nanoparticles embedded on carbon support) undergoes local potentials 1 -1.5 V caused by a combination of fuel (H 2 ) starvation, mixed fuel region and cell reversal 2 .This leads to a series of degradation phenomenon including reduction in cathode catalyst layer (cCL) thickness and porosity, loss in electrochemical surface area (ECSA), ionomer degradation and loss in electrical contact, therefore resulting in severe performance loss 2 .The convoluted relationship between these individual degradation mechanisms, their chronology and their effects on electrochemical performance are yet unresolved.

Source

Hydrogen fuel cell technology is now being researched extensively globally to provide a stable renewable energy source in the future. New research is aiding in improving performance, endurance, cost-efficiency, and the elimination of fuel cell limitations. Throughout the development process, the many aspects impacting the features, efficiency, durability, and cost of a fuel cell must be examined in a specific method. This review study looked at the impact of several variables on hydrogen fuel cell durability (HFC). In every sphere of fuel cell application, long-term operation is a must to make this electrochemical cell work. The major durability-enhancing aspects of a fuel cell include temperature, catalytic decay, contaminants, thermal energy and water maintenance, and fuel cell component design.

Source

To achieve high efficiency of 65% LHV in the solid oxide fuel cells (SOFCs), the fuel utilization should increase to the level of over 80%, which is 10-15% higher fuel utilization (Uf) than the standard condition, and severe degradation can occur at the component materials. When the current density is controlled in the stack level, there might be the distribution of fuel utilization in the cells due to the distribution of fuel gas, water vapor pressures, and temperatures. So far, many studies were examined on the clarification of degradation mechanism under fuel cell operation. In this report, recent achievements of the Japanese national projects (NEDO projects) are presented, especially on the rapid evaluation methods for degradation (2018-2019) and most recent Development of advanced evaluation and analysis technologies for the durability of Solid Oxide Fuel Cells stacks (2020-). Especially, the anode durability was discussed with different kinds of cell-stack geometry at high fuel utilization. The degradation mechanism and fuel utilizations are compared at the planer and flat tu... Read More

Source