Design Of Proton Exchange Membrane Fuel Cell Research Articles

Evaluation criterion of cathode flow field in air-cooling proton exchange membrane fuel cells

In recent years, air-cooling proton exchange membrane fuel cells (PEMFCs) have become a priority choice for applications due to their lightweight and simple structure. In this work, the mechanism of cathode flow field characteristics on PEMFC performance is revealed, and the evaluation criterion of the cathode flow field is proposed. A 2 kW PEMFC stack of 100 cells is used, and the different uniformity and airflow rate of the cathode flow field are achieved by varying the position and number of cathode fans with a constant total parasitic fan power. The PEMFC power, cathode temperature distribution, and single-cell voltage consistency of different configurations are evaluated. The results show that the maximum difference in output power and maximum temperature of different PEMFC cathode flow field configurations reach 6.5% and 22.3%, respectively. Three key parameters are proposed to evaluate the PEMFC cathode flow field: total uniformity rate can evaluate the overall uniformity of the PEMFC cathode flow field, vertical uniformity rate can be used to predict and evaluate the single-cell voltage consistency of the PEMFC stack, and cathode airflow rate determines the continuous operating power of the PEMFC stack. The evaluation criterion can guide the design and optimization of air-cooling PEMFCs.

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.

Proton-exchange membrane fuel cell design for in-situ depth-sensitive X-ray absorption spectroscopy

We have built a proton exchange membrane hydrogen fuel cell optimized for angle-resolved X-ray absorption spectroscopy. This cell allows in-situ fluorescence measurements during electrochemical operation with minimal trade-offs in cell performance while reaching automotive current densities. The fluorescence signal can be collected from wide angles to extract depth information from the probed atomic species such as Pt, Co, and Ni, crucial to highly efficient FC. This cell is designed to assess the connection between the ionic drag/diffusion and the performance loss by following the real-time movement of the species through the membrane electrode assembly.

A 3D PtCo degradation model for long-term performance prediction of a scaled-up PEMFC under constant voltage operation

The non-uniform distribution of reactants, pressure, temperature and reaction rate in a scaled-up proton exchange membrane fuel cell (PEMFC) can lead to different catalyst degradation rate, impacting the long-term performance of PEMFCs. However, the local catalyst degradation behaviors in a PEMFC stack have not yet been fully understood due to the lack of experimental approaches and catalyst degradation model. In the present study, a numerical model is established for a 200 cm2 commercial-sized PEMFC stack with realistic anode and cathode flow fields. PtCo is employed as the cathode catalyst, and a 3D PtCo catalyst degradation model is developed to analyze the non-uniform evolution of the electrochemical active surface area (ECSA), current density, and Co2+ in the catalyst layers under the constant voltage conditions. The modeling results demonstrated that catalyst degradation is more severe downstream as well as under land of the cathode flow field, and the cathode catalyst layer (CCL) is the area most contaminated by the Co2+. The non-uniform catalyst degradation as well as Co2+ contamination increased the activation losses and local oxygen transport resistance. The catalyst degradation leads to a total power loss of 43.3 % after 80,000 h operation. The aging model provides a better understanding for large scale PEMFC stacks regarding its non-uniform PtCo degradation and can assist the future design of commercial PEMFCs with better lifetime.

Enhancing heat dissipation and mass transfer of oxygen gas flow channel in a proton exchange membrane fuel cell using multiobjective topology optimization

To enhance the heat dissipation and mass transfer from a proton exchange membrane fuel cell (PEMFC) stack, a multi-objective topology optimization model considering structural deformation, heat transfer, mass diffusion, and gas flow process is proposed herein. The average molar concentration of oxygen and average temperature in the cathode catalyst layer (CL) are considered as the optimization objectives, and the mechanical, mass transfer, and gas flow properties are treated as constraints. The results reveal that compared with a straight gas channel, the topology-optimized configuration leads to an improvement in oxygen molar concentration by 10.36% and reduction in average temperature by 2.26 K. A higher power-dissipation constraint leads to a more complex three-dimensional channel structure with more branches. A larger structural displacement constraint results in a wider and flatter flow channel topology. The average oxygen molar concentration of topologically optimized configurations increases ranging from 5.18 to 14.96%, and the average temperature in the CL decreases about 2.2 K, compared with that of straight gas channel configurations, when the velocity at inlet varies from 0.05 to 0.3 m/s. These findings can aid in the design of PEMFCs.

Investigating the Parameter-Driven Cathode Gas Diffusion of PEMFCs with a Piecewise Linearization Model

Improving mass transfer in gas diffusion layers is critical to achieving high-performance proton-exchange membrane fuel cells (PEMFCs). Leaks through the interface between the gas and the membrane electrode assembly frame have been widely investigated, and the controllability of the cathode gas diffusion has not been achieved in most studies. In this study, we develop a structural parameter to investigate the controllability of the gas diffusion mechanism in the cathode in order to improve upon the design and performance of PEMFCs. This parameter accounts for the cathode gas diffusion layer porosity and carbon loading inside the catalyst layer. It is comprehensively calculated to relax the two segments’ distribution along three directions of the coordinate axis. The experimental and simulation results show that the obtained values of the parameter vary and change during voltage stabilization. According to the results, regardless of the materials in the cathode gas diffusion layer, the same steady-state voltage is obtained when the parameter is fixed. The cell could be controllably operated for a wide range of diffusion layer thicknesses by selecting the optimal parameter.

Improved flow field design for air-cooled proton exchange membrane fuel cells

ABSTRACT As a portable power source, air-cooled proton exchange membrane fuel cells (PEMFCs) have the advantages of high energy density, low weight, and zero-emission. However, direct supply of ambient air by fan may cause high local temperature and membrane electrode dehydration, resulting in unstable performance and durability issues. In this study, the air flow field design of air-cooled PEMFCs is compared and optimized aiming to improve the mass and heat transfer characteristics. For this purpose, a three-dimensional, multi-disciplinary, non-isothermal numerical model is developed and validated through experimental tests of an in-house developed 800 W air-cooled PEMFC stack. It is revealed that the PEMFC performance, especially under high current load conditions, can be improved by increasing the channel depth. The obtained results indicate that the higher rib-channel width ratio is favorable to air-cooled PEMFC performance, but it may lead to considerable non-uniform distributions of temperature and current density. Moreover, the effectiveness of utilizing the zigzag flow channel for air-cooled PEMFCs is assessed. It is found that the best cell performance can be obtained when the tilt angle of zigzagged flow field equals to 2.5°.

Water management in a novel proton exchange membrane fuel cell stack with moisture coil cooling

Water flooding causes severe degradation of the performance and lifetime of proton exchange membrane fuel cell (PEMFC). In this study, a novel PEMFC stack with in-built moisture coil cooling was designed and the effects of moisture coil cooling on water management in the new PEMFC stack under various operating conditions were investigated. The result showed that the performance of the PEMFC stack was significantly improved due to the moisture condensation under high current density, high operating temperature, high relative humidity and high operating pressure. The output power was increases by 21.62% (525.71 W) at 1600·mA cm−2 while the increased parasitic power was no more than 35W. Moreover, degradation of the cathode catalyst layer after 100 h operation was also reduced by using moisture coil cooling. Compared with the situation without moisture condensation, the maximum decay rate of the cathode catalyst layer thickness after 100 h operation was reduced by 13.01%. Accordingly, the novel design is valuable and can be widely used in the future design of PEMFC.

Micromodification of the Catalyst Layer by CO to Increase Pt Utilization for Proton-Exchange Membrane Fuel Cells.

Improving the utilization of platinum in proton-exchange membrane (PEM) fuel cells is critical to reducing their cost. In the past decade, numerous Pt-based oxygen reduction reaction catalysts with high specific and mass activities have been developed. However, the high activities are mostly achieved in rotating disk electrode (RDE) measurement and have rarely been accomplished at the membrane electrode assembly (MEA) level. The failure of these direct translations from RDE to MEA has been well documented with several key reasons having been previously identified. One of them is the resistance caused by complex mass transport pathways in the MEA. Herein, we improve the proton and oxygen transportations in the MEA by building a thin and uniform distribution of ionomer on the catalyst surface. As a result, a PEM fuel cell design is capable of showing a current density improvement of 38% at the same voltage (0.6 V) under the H2/air operation.

Image recognition of cracks and the effect in the microporous layer of proton exchange membrane fuel cells on performance

Proton exchange membrane fuel cell (PEMFC) is considered as a potential power source for future automotive applications and microporous layer (MPL) is one of the core components. The cracks on the surface of microporous layer formed during the deposition process change the overall transport capacity and effect the output performance of fuel cells by regulating water management. In this work, the image recognition and feature extraction of microporous layer surface crack is proposed and elaborated in detail. The simple, fast and accurate method based on image recognition is realized by programming a regional connectivity algorithm and calculating the geometric features of the circumscribed geometry of the cracks. The application of artificial intelligence image processing technology at the micron level provides convenience for data analysis of crack distribution and improvement of microstructure. In this paper, scanning electron microscope (SEM) images of different carbon paper samples are taken, and the samples are tested under the same conditions to verify the feasibility and accuracy of the crack identification method, and to study the effect of cracks on the performance of fuel cells. The results prove that the image recognition algorithm can quickly and accurately identify the characteristics of cracks after Gaussian filtering and grayscale thresholding. Besides, it is found that cracks have impact on fuel cells and surface slender-shaped cracks with large area can improve the performance of fuel cells at high current densities. The method proposed in this paper can be used to improve the existing PEMFC design and quality check in process production by analyzing the local crack characteristics of the same sample and statistical data. In addition, the results of this paper are instructive for further water management research on microporous layer in fuel cells and can be used as a reference for practical applications.

Characterizing the two-phase flow effect in gas channel of proton exchange membrane fuel cell with dimensionless number

A simplified one-dimensional proton exchange membrane fuel cell (PEMFC) model is developed to characterize the two-phase flow effect with dimensionless numbers. A new Damköhler number is defined to decouple the gas and liquid flow in electrodes. The flow pattern in gas channels can be predicted by force balance analysis with Reynolds number and Weber number. The effect of two-phase flow patterns in bipolar plate gas channel on mass transfer at the gas channel-gas diffusion layer (CH-GDL) interface can be represented by Sherwood number. Then, the influence of relative humidity, cathode stoichiometric ratio, operating temperature and dimensionless width of water film/slug are studied. The results indicate that the two-phase flow occurring at high humidity and current density can be accurately predicted with dimensionless numbers. The output performance of fuel cell dropped by 10–100 mV due to the additional mass transfer resistance caused by liquid water in bipolar plate gas channels. Therefore, the present model can reflect the main two-phase transport effects with low computational cost and contribute to the efficiency and accuracy of PEMFC design and control.

Wave-shaped flow channel design and optimization of PEMFCs with a groove in the gas diffusion layer

The effects of the wave-shaped flow channel structure and a groove in the gas diffusion layer (GDL) on the net power density of proton-exchange membrane fuel cells (PEMFCs) are investigated. A three-dimensional, two-phase, steady-state, and isothermal numerical model of PEMFCs is established. The amplitude and the number of wavy cycles play an important role in improving the performance of fuel cells, and the optimization of the wave-shaped flow channel to obtain the optimal flow channel structure is performed using the genetic algorithm. Furthermore, regarding the optimal wave-shaped channel, the mass transfer effect can be improved by introducing a groove structure into the GDL for gas diffusion. Thus, two parameters, i.e., groove position and depth, are optimized, and the output power and power consumption are also considered. According to the results, the wave-shaped flow channel with a groove in the GDL exhibits high efficiency. The optimal flow channel has an amplitude of 0.643 mm, the number of wavy cycles of 9, and the groove position and depth of 9.5 and 0.05 mm, respectively, and the net power density can be increased by 2.64%.

Preparation and Characterisation of Microporous Layers Derived from Graphene Foam

Proton exchange membrane fuel cells (PEMFC) are a viable means to meet global energy demand, reduce dependence on fossil fuels, and mitigate carbon dioxide emissions. Despite recent progress in their development, water saturation remains a challenge to current PEMFC design and efficiency. The addition of a microporous layer improves fuel cell performance largely from the reduction of water accumulation and the enhancement of mass transfer capacity at high current densities. However, optimisation of the microporous layer is necessary to improve its capability to manage liquid water and facilitate mass transfer. In this study, the viability of microporous layers produced from synthesised graphene foams was assessed.Graphene foam was synthesised from the pyrolysis of sodium ethoxide, the resulting carbon was then subject to pyrolysis in different atmospheres in order to enhance the conductivity. The graphene foams underwent characterisation by electron microscopy and x-ray fluorescence which showed high carbon purity open foams with micron scale pores and graphene-thin walls. Microporous layers were then produced from these graphene foams, commercial graphene and from carbon black; they were then characterised ex-situ and through polarisation curves.Ex-situ characterisation of the microporous layers was used to determine the micro-structure and physical properties, as well as its ability to repel liquid water and to conduct electron and mass transfer. Electron microscopy and mercury intrusion porosimetry enabled the analysis of morphology and microstructure, and the transport properties of the layer were determined through permeability, electrical conductivity and contact angle measurements. Polarisation curves were performed at low and high relative humidities in order to understand the capability of these microporous layers in a range of operating conditions. Figure 1

A metaheuristic-based methodology for efficient system identification of the Proton Exchange Membrane Fuel Cell stacks

In this study, a new procedure for optimum and effective system identification of Proton Exchange Membrane Fuel Cell (PEMFC) stacks is introduced. The present study proposes a method to obtain the optimum amount of the uncertain parameters of the PEMFC design to deliver the uppermost confirmation with the real output voltage value. To do so, the integral of the absolute error (IAE) between the real and model outputted voltage values is considered an objective function. To minimize this function, a modified design of the emperor penguin optimizer has been suggested. The method has been then investigated by performing two real case study models and its achievements are put in comparison with several latest techniques to show the method's productivity. The achievements show that the suggested technique has a higher ability for parameter estimation of the PEMFC models.

Rationalizing Structural Hierarchy in the Design of Fuel Cell Electrode and Electrolyte Materials Derived from Metal-Organic Frameworks

Metal-organic frameworks (MOFs) are arguably a class of highly tuneable polymer-based materials with wide applicability. The arrangement of chemical components and the bonds they form through specific chemical bond associations are critical determining factors in their functionality. In particular, crystalline porous materials continue to inspire their development and advancement towards sustainable and renewable materials for clean energy conversion and storage. An important area of development is the application of MOFs in proton-exchange membrane fuel cells (PEMFCs) and are attractive for efficient low-temperature energy conversion. The practical implementation of fuel cells, however, is faced by performance challenges. To address some of the technical issues, a more critical consideration of key problems is now driving a conceptualised approach to advance the application of PEMFCs. Central to this idea is the emerging field MOF-based systems, which are currently being adopted and proving to be a more efficient and durable means of creating electrodes and electrolytes for proton-exchange membrane fuel cells. This review proposes to discuss some of the key advancements in the modification of PEMs and electrodes, which primarily use functionally important MOFs. Further, we propose to correlate MOF-based PEMFC design and the deeper correlation with performance by comparing proton conductivities and catalytic activities for selected works.

Improving Parameter Estimation of Fuel Cell Using Honey Badger Optimization Algorithm

In this study, we proposed an alternative method to determine the parameter of the proton exchange membrane fuel cell (PEMFC) since there are multiple variable quantities with diverse nonlinear characteristics included in the PEMFC design, which is specified correctly to ensure effective modeling. The distinctive model of FCs is critical in determining the effectiveness of the cells’ inquiry. The design of FC has a significant influence on the simulation research of such methods, which have been used in a variety of applications. The developed method depends on using the honey badger algorithm (HBA) as a new identification approach for identifying the parameters of the PEMFC. In the presented method, the minimal value of the sum square error (SSE) is applied to determine the optimal fitness function. A set of experimental series has been conducted utilizing three datasets entitled 250-W stack, BCS 500-W, and NedStack PS6 to justify the usage of the HBA to determine the PEMFC’s parameters. The results of the competitive algorithms are assessed using SSE and standard deviation metrics after numerous independent runs. The findings revealed that the presented approach produced promising results and outperformed the other comparison approaches.

Artificial intelligence-based multi-objective optimisation for proton exchange membrane fuel cell: A literature review

Proton exchange membrane fuel cells (PEMFCs) are promising devices for converting chemical energy into electrical energy due to their versatile properties, such as high power density, quick start-up, lower operating temperature, portability, etc. For PEMFC technology to outperform the incumbent technologies, artificial intelligence (AI) based multi-objective optimisation (AI-MOO) has been employed to facilitate the design and applications of PEMFC since AI-MOO is flexible enough to consider various factors simultaneously in the customized multiple objective functions and under new or updated case situations. This review provides a comprehensive literature survey on AI-MOO employed in the PEMFC field. Firstly, AI-MOO were introduced in detail, including the definition, categories and framework. Then the objectives, intelligent algorithms and trade-off methods commonly used in PEMFC were tabularised and evaluated. The application of AI-MOO in PEMFC was summarised systematically based on the application areas, including the PEMFC components, kinetics and thermodynamics, control and monitoring systems, the overall performance, and the hybrid systems. The related studies were tabularised and discussed, especially algorithms, variables, objectives and optimisation results. Finally, this review addressed the current challenges in the research area and proposed research implications for future investigations.

Predicted Impacts of Catalyst Layer Ionomer Microstructure and Distribution on PEMFC Performance

Electric vehicles powered by proton exchange membrane fuel cells (PEMFCs) are a promising means to reduce environmentally harmful emissions. PEMFCs offer low weight, high range (miles traveled before refueling), and quick refueling times; however, persistent technical challenges limit commercialization of fuel cell electric vehicles (FCEVs). In addition to system-level challenges such as an immature refueling infrastructure and H2 production, it remains challenging to manufacture low-cost PEMFCs that meet durability and performance requirements. Addressing the performance issues of low-cost PEMFCs has proven difficult due to a gap in understanding physiochemical resistances within the heterogeneous catalyst layer (CL).Electrochemical reactions occurring in the CL—and therefore PEMFC performance—depend in complex ways upon the CL microstructure. Reactants and products are transported to and from Pt catalysts through nano-thin films of Nafion ionomer, which coat carbon-dispersed Pt catalysts. Through the use of neutron reflectometry (NR) [1,2] and conductivity measurements [3], previous studies show that the structure and material transport properties of Nafion are linked and depend on multiple factors including film thickness, substrate interactions, temperature, and relative humidity. Previously [4], we developed pseudo-2D Newman-type computational models that incorporate novel structure-property relationships derived from these studies. The results concluded that increasing the ionomer film thickness surrounding Pt-covered carbon particles in the CL may lead to a higher PEMFC performance due to an increased conductivity caused by increased ionomer volume fraction and increased Nafion water absorption.In this presentation, we extend our previous model to further advance understanding of how ionomer structure and distribution influence PEMFC performance. The current modeling efforts include two-phase water transport to understand the role of flooding in performance limits under low-Pt loading. Additionally, structure-property relationships from our previous work are updated to include more relevant structures taken from NR experiments performed with Nafion on technologically relevant substrates (Pt and carbon). Presented results will demonstrate the predicted impacts of non-uniform ionomer distribution within the cathode CL, including novel design concepts such as ionomer-rich regions to enhance ion transport for increased catalyst utilization further from the membrane. These predicted impacts provide insight for future PEMFC design modifications to accelerate FCEV commercialization.[1] J. A. Dura, V. S. Murthi, M. Hartman, S. K. Satija, and C. F. Majkrzak, “Multilamellar Interface Structures in Nafion,” Macromolecules, vol. 42, no. 13, pp. 4769–4774, 2009.[2] S. C. DeCaluwe, A. M. Baker, P. Bhargava, J. E. Fischer, and J. A. Dura, “Structure-property relationships at Nafion thin-film interfaces: Thickness effects on hydration and anisotropic ion transport,” Nano Energy, vol. 46, pp. 91–100, 2018.[3] D. K. Paul, R. McCreery, and K. Karan, “Proton Transport Property in Supported Nafion Nanothin Films by Electrochemical Impedance Spectroscopy,” Journal of The Electrochemical Society, vol. 161, no. 14, 2014.[4] C. R. Randall and S. C. DeCaluwe, “Physically Based Modeling of PEMFC Cathode Catalyst Layers: Effective Microstructure and Ionomer Structure-Property Relationship Impacts,” Journal of Electrochemical Energy Conversion and Storage, vol. 17, no. 4, 2020.

Non-Fourier Heat Conduction and Thermal-Stress Analysis of a Spherical Ice Particle Subjected to Thermal Shock in PEM Fuel Cell at Quick Cold Start-Up

Quick start at low temperature is one of the key bottleneck technologies that restrict the large-scale commercialization of proton exchange membrane (PEM) fuel cell vehicles. Ice and devices in battery systems based on thermal deicing are inevitably subjected to thermal shock. In order to study this problem, a non-Fourier heat conduction model is established to study the temperature response of a spherical ice particle subjected to thermal shock with different boundary conditions on the surface. Furthermore, distribution of thermal stress in the particle is obtained using the calculated temperature field, and the effect of thermal relaxation time and boundary conditions on the temperature response as well as the thermal stress field are also analyzed. The results, which are significantly different from that obtained using Fourier law of heat conduction, show that the mechanical stresses and the serious expansion of the ice particle may lead to the severe deformation of the devices connected to the ice during the cold start-up, imposing a great challenge in controlling structural reliability of PEM fuel cells. The numerical results are expected to provide a scientific theoretical basis for PEM fuel cell design and low-temperature start-up control.

Stress response and contact behavior of PEMFC during the assembly and working condition

Mechanical behavior of proton exchange membrane fuel cell (PEMFC) is closely related to its service life. Stress response and contact behavior of PEMFC during the assembly and working condition were investigated. Effects of clamping force, steel bands number and width on the mechanical behavior of PEMFC were discussed. Thermal-mechanical coupling was considered during the PEMFC working for thermal effect caused by chemical reaction. The results show that stress distribution of multi-cells is more uniform after assembly. Stress and contact pressure distributions of single-cell and multi-cells are similar after assembly. During the assembly process, the average contact pressure between the MEA and other parts increases with the increasing of clamping force, steel band width and number. With the steel bandwidth increases, the contact pressure distribution of MEA is more uniform. And the chemical reaction inside the fuel cell is more favorable. Stress concentration is prone to appear on the corners of GDL on the MEA, corners of sealing gasket, and edges of bipolar plate ribs, which may cause seal failure after long-term work. Under working condition, thermal expansion can enhance the sealing performance, but affect stress of bipolar plate and MEA. Those results can be used for design, manufacturing, maintenance and evaluation of PEMFC.