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The dynamic performance of Proton Exchange Membrane Fuel Cell (PEMFC) is crucial for safe and efficient operation and remains a major barrier to commercialization. In this paper the dynamic response characteristics of PEMFC under serpentine flow field (SFF) and parallel flow field (PFF) are discussed. The effects of current loading, operating pressures, anode and cathode stoichiometric ratios, as well as operating temperatures on the dynamic response characteristics of PEMFC are systematically studied through experimental methods. Furthermore, the principle and mitigation strategies for voltage undershoot are investigated. It shows that lower current density, higher back pressure and higher temperature are benefit to alleviate voltage undershoot. Compared with the SFF, the Second-stage time delay of PFF is shortened by 9.2 s, the VU is decreased by 17.27 mV, and the energy loss is reduced by 0.71%. Moreover, Pearson correlation coefficient is proposed to evaluate the correlation between index and PEMFC performance. The dynamic response characteristics of PEMFC under serpentine flow field and parallel flow field are systematically studied through experimental methods. And the principle and mitigation strategies for voltage undershoot are investigated. It is aim to provide guiding significance for the application of flow field structure and current loading conditions. [Display omitted] • The dynamic response characteristics of PFF and SFF during loading are investigated in terms of parameters. • The mechanism of the flow field structure on the amplitude of the voltage downshoot is discussed. • An optimal control strategy for the loading and operating parameters with low energy loss is proposed. • PCC is proposed to evaluate the overall performance of PEMFC. [ABSTRACT FROM AUTHOR]

Graphite composite bipolar plate (BP) have limited conductivity, which makes them less than ideal for extensive application in proton exchange membrane fuel cell (PEMFC). In traditional graphite composite BP, the construction process of the conductive network is entirely random. To enhance conductivity, it is typically necessary to increase the content of conductive fillers or incorporate high aspect ratio carbon nanomaterials to optimize the density of the conductive network. In this work, we manufactured a highly conductive composite bipolar plate with synergistic conductive networks of graphite and metal foam (MF). With a synergistic conductive network, the ASR of CuG80-20ppi decreased to 7.7 mΩ cm2. Additionally, thermal conductivity increased to 24.76 W/(m·K), and in-plane conductivity reached 294.1 S/cm at 80 wt% mass fractions of conductive filler, using 20 ppi copper foam as the metallic conductive network. CuG80-20ppi exhibited a flexural strength of 52.2 MPa. G80 and CuG80-20ppi have the 80 wt% conductive filler and are molded into BP with parallel flow fields. CuG80-20ppi enhances the current density of PEMFC by 0.132 W/cm2 and reduces the ohmic impedance by 5.25%. Therefore, the findings of this study offer valuable insights for the enhancement of composite BP conductivity, while simultaneously ensuring the stability and continuity of the synergistic conductive network. A novel approach is presented to enhance the electrical conductivity of graphite composite bipolar plate (BP) for proton exchange membrane fuel cells (PEMFCs). By embedding metal foam as a supplementary conductive network within the graphite matrix, a synergistic conductive architecture is achieved. This innovation significantly reduces the area specific resistance (ASR) to 7.7 mΩ cm2 and boosts thermal conductivity to 24.76 W/(m·K). The resulting CuG80-20ppi BP, with 80 wt% conductive filler, exhibits improved mechanical strength and conductivity, contributing to a 0.132 W/cm2 increase in PEMFC current density and a 5.25% reduction in ohmic impedance. This work highlights the potential of metal foam integration to enhance BP conductivity and PEMFC performance. • A novel synergistic conductive network is introduced to develop bipolar plates. • This conductive network is constructed from graphite and metal foam. • It can achieve rapid and regular electronic transfer by metal and graphite. • Bipolar plate was optimized for brittleness by incorporating metal foam. • PEMFCs with this novel bipolar plate reduces Ohmic polarization by 5.25%. [ABSTRACT FROM AUTHOR]

ABSTRACT The problem of air feed system control with guaranteed prescribed performance and fixed time control is investigated for proton exchange membrane fuel cell (PEMFC). First of all, the original model of PEMFC air feed system is converted to fully actuated system using higher order fully actuated system (HOFAS) approach. A fixed time extended state observer (ESO) is employed to approximate the cathode pressure. The parameter uncertainty is compensated by an adaptive radial basis function neural network (RBFNN). Then a prescribed performance sliding mode controller is designed with fixed convergence time. The proposed control law could guarantee the prescribed transient response for oxygen excess ratio (OER) error under stack current changing and bounded uncertainty. Lyapunov approach is utilized to proof fixed‐time stability of proposed controller. Simulation results of the study tests illustrate that the presented controller is efficient under constant OER tracking control, constant OER tracking control with parameter perturbation, and variable OER tracking control, respectively. [ABSTRACT FROM AUTHOR]

Fuel cells (FCs) have attracted significant interest due to their versatile applications, but modeling their nonlinear behavior is challenging. This research proposes an Enhanced Artificial Hummingbird Algorithm (EAHA) to identify the seven unknown parameters of proton exchange membrane fuel cell (PEMFC) stacks using their experimental data. The goal is to accurately predict the current/voltage (I/V) curves by minimizing a cost function defined as the sum of squared differences between measured data points and model estimates. The EAHA combines several territorial foraging techniques with a linear regulation mechanism. Its performance is compared to the conventional Artificial Hummingbird Algorithm (AHA) using three common PEMFC modules. Additionally, a comparative analysis is performed against previously published methods and newly developed optimizers like Particle Swarm Optimizer (PSO), Grasshopper Optimization Algorithm (GOA), Atom Search Optimization (ASO), Grey Wolf Optimizer (GWO), and parental algorithm i.e., Artificial Hummingbird Algorithm (AHA). The findings showcase the proposed approach's efficacy relative to existing methods and state-of-the-art optimizers. The two models are taken for the checking of reliability and performance of the PEMFC. The results are also compared with the Non-Parametric tests and it is concluded that the proposed algorithm is far better than the rest of the compared algorithms in both the models. [ABSTRACT FROM AUTHOR]

Non‐precious metal‐based nitrogen‐doped carbon (M‐Nx/C) shows great potential as a substitute for precious metal Pt‐based catalysts. However, the conventional pyrolytic methods for forming M‐Nx/C active sites are prone to issues such as the lack of synergistic interactions among bimetallic atoms and the potential encasement of active sites, leading to compromised catalytic efficiency and hindered mass transfer. In this work, a highly active FeCo‐N‐C@U‐AC electrocatalyst is developed with a high density of active sites, adequate exposure of catalytic sites, and robust mass transfer capability using the chemical vapor‐phase deposition (CVD) technique. The resulting catalyst demonstrates impressive oxygen reduction reaction (ORR) catalytic performance and stability, with half‐wave potentials of 0.820 V (0.1 M HClO4) and 0.911 V (0.1 M KOH), respectively. It also exhibits significantly enhanced stability, retaining 93.25% and 98.38% of current after continuous 50 000 s of durability testing, surpassing the retention rates of Pt/C (80.31% in HClO4 and 84.96% in KOH electrolytes). Notably, when employed as a cathode catalyst in proton exchange membrane fuel cells (PEMFCs) and zinc‐air flow batteries (ZAFBs), the FeCo‐N‐C@U‐AC catalyst delivers peak power densities of 859 and 162 mW·cm−2, respectively, showcasing competitive performance comparable to benchmark Pt/C. [ABSTRACT FROM AUTHOR]

One of the most critical components of a proton exchange membrane (PEM) fuel cell is the gas diffusion layer (GDL). Conventional preparation methods are complex, energy-consuming, and lack design flexibility. Additive manufacturing (AM) is widely used in various fields, with the fused deposition modeling (FDM) technique being the most widely used. With AM, GDLs can be designed and printed with precise control over their structure, porosity, and thickness. Previous research by the authors has shown high electrical resistance of the FDM-printed GDL. Thus, in this study, surface modification of printed GDL was performed to enhance its performance. The FDM-printed GDL with conductive graphite coating demonstrated a desirable breaking factor (2.11 kN/m) and air permeability (326 cm3/cm2/s). Its thickness, mass, and porosity were also determined to be appropriate and customizable. The performance of the manufactured GDL was examined in an open cathode air-breathing PEM fuel cell, indicating good feasibility at room temperature (20 °C). The results show that the application of the FDM technique in GDL manufacturing has great potential to revolutionize the fuel cell industry and drive progress toward a more sustainable future. [ABSTRACT FROM AUTHOR]

Proton exchange membrane (PEM) fuel cell air supply system is primarily responsible for delivering air to the fuel cell at a specific stoichiometric ratio for chemical reaction. The stoichiometric ratio will be impacted by the sudden change in load and system failure. Under the aforementioned circumstances, precise and timely air supply regulation is required to avoid irreparable PEM damage. In order to enhance the robustness and performance of the fuel cell, a cascaded finite time sliding mode fault‐tolerant control method is proposed for the air supply system of PEMFC. The control objective is to adjust the oxygen excess ratio at the cathode flow field, which can avoid the occurrence of oxygen starvation in the PEM fuel cell when the load current changes rapidly or when fault occurs. A cascaded controller structure is introduced, where, in the inner loop, an adaptive sliding mode controller is designed to reconstruct fault signal and track the optimal output trajectory and, in the outer loop, a finite‐time observer is employed to obtain the expected output trajectory. The proposed control scheme is capable of fault‐tolerant tracking of the optimal oxygen excess ratio within finite time. The effectiveness of proposed fault‐tolerant control algorithm is verified through hardware‐in‐the‐loop (HIL) studies. [ABSTRACT FROM AUTHOR]

In a fuel cell, flow channels are crucial components responsible for various essential functions that enable the system to operate effectively. The design of a directly coupled flow channel in a Proton Exchange Membrane Fuel Cell (PEMFC) system, assuming deterministic parameters, has been extensively studied. However, this deterministic approach neglects the inherent uncertainties in system performance during real-life operation, resulting in potentially unreliable and suboptimal performance. To address this issue, we propose a reliability-based design optimization (RBDO) of the PEMFC's channel structure, considering uncertainties in operating parameters. This paper presents a numerical model of the PEMFC in COMSOL, deterministic designs, reliability-based designs and a global sensitivity analysis on the PEMFC cell's potential output and average water activity on the membrane. Although the RBDO approach shows a reduction in cell efficiency compared to the deterministic design, it significantly improves reliability, with increases from 60.92% to 95.10% for cell potential and from 79.31% to 96.85% for water activity. [ABSTRACT FROM AUTHOR]

Bipolar plates (BPPs) and membrane electrode assemblies (MEAs) are the key components for proton exchange membrane fuel cells (PEMFCs), they are alternately arranged to construct a compact stack with high power generation. This stacking method may introduce several issues, such as the difficulties in maintenance, imprecise assembly and sealing. This paper presents a novel integrated packaged single fuel cell that employs titanium metal bipolar plates to construct a short stack with superior sealing performance and working reliability. To predict the performance of integrated packaged single cell, numerical model was developed to analyze the mass transfer of O 2 , H 2 and H 2 O within the cell, revealing a uniform distribution of reactants and current. A short stack was manufactured with 10 layers of single cells, it retains excellent sealing properties and consistent output across a range of pressure conditions, with a leakage rate deviation lower than 0.03 mL/(min·cell) and membrane current density variation less than 5%. Finally, the electrochemical performance of the integrated packaged short stack was tested, its maximum power is 886.67 mW/cm2. It can achieve a rated output power of 169.14 W and an energy density of 1684.97 mW/cm3. Thus, our developed short stack has high energy utilization efficiency for power generation, and is anticipated to provide a durable power source for drones, robots and new energy vehicles. • An integrated packaged single fuel cell short stack based on titanium metal polar plates was proposed. • Numerical model of single cell was established, simulation on gas molar concentration and current density distribution was conducted. • A 10-layer integrated short stack was fabricated, assembly stress and polarization tests verified its good sealing performance. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cell (PEMFC) with dead-ended anode (DEA) suffers from nitrogen diffusion and water accumulation, leading to unstable performance. The core of this paper is to enhance the stability of DEA operation. By coupling the flow field structure with the DEA mode, the factors affecting the stability are explored, the performance degradation mechanism after DEA operation is revealed, and the purging strategy is formulated by combining the energy management with the voltage stability as a prerequisite. The experimental results show that the serpentine flow field is advantageous for maintaining the most stable DEA operation with a minimum voltage recession of 17.01 mV and a voltage undershoot of 11.63 mV. The local current density distribution exhibited a pattern of highest values at anode inlet and lowest at anode outlet, which could be improved by increasing operating pressure and reducing load current density. In this experiment, PCB was innovatively combined to investigate the degradation of each region of PEMFC after 60h of DEA operation. It is found that the most severe performance degradation occurs in anode outlet with a degradation rate exceeding 50%, while the center area has a degradation rate of no more than 20%. • The flow field structures are evaluated for the most stable DEA operation. • Experimentally investigated the stability of DEA operation based on PCB segmented cell technology. • The optimized purging strategy is formulated to maintain the stability operation with high output energy. [ABSTRACT FROM AUTHOR]

In this study, we tackle the complex and unresolved challenge of optimizing the performance of membrane electrode assemblies (MEAs) in varying relative humidity environments, which is crucial for practical fuel cell technologies. To address this challenge, we developed an innovative approach by fabricating an asymmetric membrane that integrates an ultrathin layer of hydrophilic carbon nanotubes (HCNTs) on the cathode side of the proton exchange membrane (PEM). The primary objective was to enhance the dimensional stability of the membrane by reducing water flooding-induced swelling on the cathode side. Additionally, the inclusion of the carbon nanotube layer improved the interfacial affinity with the cathode electrode. As a result, the MEA constructed using the asymmetric PEM coated with 0.065 mg cm−2 HCNTs demonstrated impressive current densities of 800 mA cm−2 and 1300 mA cm−2 at 0.7 V and 0.6 V, respectively, while achieving a maximum power density of 818 mW cm−2 under 100% relative humidity (RH). Remarkably, even when the RH was reduced to 0%, the MEA maintained a current density of 1100 mA cm−2 at 0.6 V and a maximum power density of 788 mW cm−2. Furthermore, the inclusion of the HCNTs layer significantly enhanced the stability of the MEA under low RH conditions, representing a crucial advancement in extending the lifespan of fuel cells in harsh environments. The novel structure of the MEA presented in this work offers a practical and effective strategy for enhancing the performance and stability of proton exchange membrane fuel cells (PEMFCs) insensitive to changing relative humidities. • A three-dimensional interface structure is achieved by coating HCNTs onto PEM for enhanced electrochemical performance. • The MEA performance improves in low or zero humidity with an HCNTs layer on the PEM's cathode side. • The HCNTs layer enhances water management by promoting water back diffusion from the cathode to the anode. [ABSTRACT FROM AUTHOR]

The coupling effects of clamping pressure and catalyst distribution are comprehensively considered to improve proton exchange membrane fuel cell (PEMFC) performance. Numerical models were constructed to study the performance changes and the corresponding internal states of PEMFC under different clamping pressures. Since the increased clamping pressure reduces the uniformity of current density, non-uniform designs with decreased catalyst loading under channel and increased catalyst loading under rib are proposed for performance improvement. A weighted objective function considering current density magnitude and uniformity was constructed, and the performances of different catalyst loading distributions were analyzed. Compared to the uniform distribution, the optimized distribution with a variation of −15% and 15% under channel and rib had the maximum objective function value of 17.24%. The deformation analysis of the gas diffusion layer and optimization of catalyst loading distribution based on deformation analysis provided a reference for the assembly of PEMFC and the production of MEA. [ABSTRACT FROM AUTHOR]

Understanding the ice nucleation mechanism in the catalyst layers (CLs) of proton exchange membrane (PEM) fuel cells and inhibiting icing by designing the CLs can optimize the cold start strategies, which can enhance the performance of PEM fuel cells. Herein, mitigating the structural matching and templating effects by adjusting the surface morphology and wettability can inhibit icing on the platinum (Pt) catalyst surface effectively. The Pt(211) surface can inhibit icing because the atomic spacing of (211) crystalline surface is much larger than the characteristic distance of ice crystal, thereby mitigating the structural matching effects. A water overlayer on the Pt surface induced by the strong attraction of Pt can act as a template for ice layers and plays an important role in the icing process. Buckling of water overlayer due to the larger atomic spacing of (211) crystalline surface mitigates the templating effect and inhibits icing. Moreover, the water overlayer on the hydrophobic Pt(211) surface with fewer water molecules also mitigates the templating effect, which makes ice nucleation more difficult than homogeneous nucleation. These findings reveal the ice nucleation mechanisms on the Pt catalyst surface from the molecular level and are valuable for catalyst designs to inhibit icing in CL. [ABSTRACT FROM AUTHOR]

The design of the reactant gas flow field structure in bipolar plates significantly influences the performance of proton exchange membrane fuel cells (PEMFCs). In this study, we introduced four innovative U-shaped flow field designs, namely: In-Out Multi-U, Out-In Multi-U, Distro In-Out Multi-U, and Distro Out-In Multi-U. To investigate the impact of these various flow fields on PEMFC performance, we conducted computational fluid dynamics (CFD) numerical simulations, validated through model experiments. Our results indicate that the Distro Out-In Multi-U flow field offers notable advantages compared to the conventional parallel flow field (CPFF) and conventional serpentine flow field (CSFF). These benefits include reduced inlet and outlet pressures, lower liquid water content, more uniform liquid water distribution, and a more even current density distribution. Furthermore, the Distro Out-In Multi-U design demonstrates improved efficiency, consuming less H2 (91.9%) than the CSFF while achieving a higher net power density output (10.1%). As a result, for the same power output, the Distro Out-In Multi-U utilizes only 83.5% of the H2 consumed by the CSFF. In summary, the U-shaped structured flow field exhibits superior output performance, enhanced energy efficiency, and improved resistance to flooding. These findings suggest that the U-shaped flow field design holds significant potential as a reactive flow field for PEMFCs. [ABSTRACT FROM AUTHOR]

Despite its high energy density and zero-carbon emissions, the path to large commercialization for Proton Exchange Membrane Fuel Cell (PEMFC) systems faces challenges related to cost reduction, efficiency enhancement, and durability improvement. One key strategy to address these hurdles is the development of reliable control algorithms that ensure operation at the Maximum Efficiency Point (MEP) of PEMFC systems. This optimization is essential for achieving high efficiency, a crucial factor for PEMFC technology commercial viability. This work explores the experimental design, implementation, and evaluation of Maximum Efficiency Point Tracking (MEPT) control algorithms for a PEMFC system. The investigated methods span across five distinct categories: conventional, data-driven, metaheuristics, online model identification, and filter-based approaches. To assess these methods, a real-time small-scale PEMFC system test bench was built. The setup consists of 200 W open-cathode PEMFC, industrial step-up DC–DC converter, programmable load and a cost-effective measurement and monitoring unit. Merits and demerits of each method are then discussed based on different performance metrics such as tracking speed, hydrogen consumption and power stress. Comparative analysis of the results reveals that, while all the algorithms achieved a maximum electrical efficiency of about 48%, data-driven methods exhibited a superior trade-off between performance metrics. This ultimately leads to improved PEMFC durability. • Enhancing PEMFC system efficiency through the implementation of MEPT control. • A detailed design of a small-scale experimental demonstration PEMFC test bench. • Comparative analysis of MEPT techniques based on multi-index performance metrics. • Data-driven methods provide the best trade-off for improving PEMFC durability. [ABSTRACT FROM AUTHOR]

Cold start impedes widespread diffusion of fuel cell vehicles (FCVs) in regions with temperatures below zero. Alternating hydrogen pump (AHP) method, distinguished by its unlimited ohmic heating capability without generating water, has been shown to be a quick and efficient method of cold starts in both single cell and short stacks. In this paper, we continue to examine possible degradation with this novel method. For this purpose, we carefully designed three experiments with different levels of stress, aimed to separate the contribution to any degradation from major factors. It was found there was no significant difference among the three cases. AHP method incurred minimal degradation after 3600 times of equivalent −30 °C cold starts. This study concludes that AHP method is not only quick and efficient, but also highly durable, hence AHP is a promising alternative cold start strategy with great potential to facilitate the diffusion of FCVs. • Durability of PEMFC cold start adopting AHP method is investigated. • A cell with variable clamping pressure is exploited. • An accelerated stress test protocol using AHP method is adopted. • Three comparable experiments are designed to decouple degradation. • AHP method is intrinsically an ultralow-degradation cold start strategy. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cell (PEMFC) stacks may encounter performance degradation or even damage during long-term operations, while the influence of defective cells on the stack performance still remains inadequately understood. In this study, the effect of defective cells on the stack temperature distribution was experimentally investigated. Two defective cells of different defect degrees were prepared by controlling hydrogen starvation time and quantitively characterized by the polarization curves, electrochemical impedance spectroscopy (EIS), and galvanostatic charge method (GCM) tests. Results show that the presence of defective cells reduces the stack performance and the temperature distribution uniformity. The increment of stack temperature and decrement of stack temperature uniformity is more prominent (with 0.9 °C and 0.31 °C at 0.8 A cm−2, respectively) when the defective cell is located at central stack. The peak sub-cell regional temperature rise can even reach 2.9 °C. For defective cells with a relatively low degree of defect, the reverse current density is high, thus leading to an increased heat generation with the average sub-cell regional temperature increment of 0.5 °C and causing adjacent normal cells to operate at higher temperature. For defective cells with an excessive degree of defect, polarization reverse occurs at low current densities, resulting in significant voltage losses and reduced performance of the stack. The present results are insightful for developing thermal management strategies for the long-term operation of PEMFC stacks. • Effect of defective cells on stack temperature distribution was experimentally studied. • Defective cells were quantitively analyzed by polarization curves, EIS, and GCM. • Stack with defective cells had higher temperature and lower temperature uniformity. • Defective cells located at central stack should be paid particular attention. [ABSTRACT FROM AUTHOR]

Fuel cell systems often utilize a hydrogen recirculation system to redirect and transport surplus hydrogen back to the anode, which enhances fuel consumption and boosts the efficiency of the fuel cell. Hydrogen recirculation pumps and ejectors are the most investigated systems. Ejectors are gaining recognition as an essential device in fuel cell systems. However, their application in hydrogen recirculation systems is often limited by a narrow operational range. Therefore, it is advantageous to compile the present condition of the study on various ejector shapes as well as configurations that can accommodate a broader operational range, along with the numerical simulations employed in these studies. This paper begins by examining the structure and operation of ejectors. It then compares and analyzes the latest advancements in research on ejector-based hydrogen recirculation systems with extended operating ranges and reviews the details of numerical simulations of ejectors, which are crucial for the development of innovative and efficient ejectors. This study provides key insights and recommendations for integrating hydrogen ejectors into the hydrogen cycle system of fuel cell engines. [ABSTRACT FROM AUTHOR]

Pt-based intermetallic compound (IMC) nanoparticles have been considered the most promising catalysts for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFC). Herein, we propose a strategy for producing ordered Pt3(CoNi) ternary IMC nanoparticles supported on N-doped carbon materials. Particularly, the Co and Ni are originally embedded into ZIF-derived carbon, which diffuse into Pt nanocrystals to form Pt3(CoNi) nanoparticles. Moreover, a thin layer of carbon develops outside of Pt3(CoNi) nanoparticles during the cooling process, which contributes to stabilizing the Pt3(CoNi) on carbon supports. The optimal Pt3(CoNi) nanoparticle catalyst has achieved significantly enhanced activity and stability, exhibiting a half-wave potential of 0.885 V vs reversible hydrogen electrode (RHE) and losing only 16 mV after 10,000 potential cycles between 0.6 and 1.0 V. Unlike the direct-use commercial carbon (VXC-72) for depositing Pt, we utilized ZIF-derived carbon containing dispersed Co and Ni nanocluster or nanoparticles to prepare ordered Pt3(CoNi) intermetallic catalysts. [ABSTRACT FROM AUTHOR]

A polymer electrolyte membrane is a core component of proton exchange membrane fuel cell. Since the ionic conductivity of polymer electrolyte membrane depends on water content, it is necessary to understand the water transport mechanism in the polymer electrolyte membrane. When the electric current demand is varied rapidly, the transient water transport results in the shortage or flooding in the polymer electrolyte membrane. The transient behavior of water transport in the polymer electrolyte membrane is nonlinear due to the water sorption/desorption mechanism. In this study, the nonlinear water transport mechanism of polymer electrolyte membrane is established to understand the transient behavior of water transport over the rapid change of electric current. Since the nonlinear dynamics delay the response of water transport under rapid change of electric current, system-level simulation is conducted to evaluate the system response by delayed water transport. Results show that the rapid change of electric current dramatically affects the water transport dynamics. As a result, this study confirms that water transport in the electrode is delayed depending on the polymer electrolyte membrane (PEM) thickness and that flooding occurs in the cathode depending on the relative humidity at the anode inlet. [ABSTRACT FROM AUTHOR]

This study focuses on the analysis of the different polarization losses in proton exchange membrane fuel cells (PEMFCs) during idling by using the distribution of relaxation times (DRT) method quantitatively. By varying operating parameters, cathodic mass transfer and oxygen reduction reactions were identified as the primary contributors to cathode mass transfer process (P1 peaks) and charge transfer process (P2 peaks) respectively. The resistance values for each polarization were obtained by fitting areas of the DRT peaks and compared with I–V steady-state values to validate the accuracy of the method. The effect of idling conditions on PEMFC attenuation at different current densities was analyzed. The result shows that during idle aging, cathode catalytic layer activation resistance growth accounts for 55% at 0.4 A cm−2, cathode mass transfer resistance for 31.2%, and Ohmic resistance for 13.7%.The electrochemically active area decreased by 16.7% from 27.32 to 22.77 m2 g−1. DRT can quickly and accurately identify the main reason for PEMFC deterioration. [ABSTRACT FROM AUTHOR]

This work presents simple post-treatment methods to selectively and partially remove the Pd core of Pd–Pt core–shell (Pt@Pd/C) catalysts. The proton exchange membrane fuel cell with the post-treated Pt@Pd/C cathode (Pt loading: 0.10 mg·cm−2) delivers an impressive peak power density of 1.2 W·cm−2. The partial removal of Pd core endows an ultrahigh oxygen reduction reaction (ORR) mass activity of 0.32 A·mgPGM−1 when normalized to the platinum group metal (PGM) mass, or equivalently 0.55 A·mgPt−1 at 0.9 V measured in a fuel cell. The post-treatment thickens the Pt shells and mitigates the Pd dissolution during potential cycling. As a result, the post-treated core–shell catalyst demonstrates superior durability in ORR mass activity and polarization power density retention than untreated core–shell catalyst and benchmark Pt/C. In-situ inductively coupled plasma-mass spectrometry (ICP-MS) results highlight that the amount of dissolved Pd in post-treated core–shell catalyst is 17-times lower than that of the untreated one. Our findings highlight the importance of structural tuning of catalysts in enhancing their mass activity and durability. [ABSTRACT FROM AUTHOR]

This research used bibliometric method to analyze the development characteristics of PEMFC during the past 10 years from 2014 to 2023. The results show that the number of articles related to PEMFC in both the CNKI database and the WOS database has a steady growth trend. The top 20 units in terms of the number of articles in the CNKI database were universities and scientific research institutions, and the Wuhan University of Technology came first. In the WOS database, the number of papers published, the number and ranking of highly cited papers, and the in-depth analysis index and ranking of cited references from China were all first. China has the largest cumulative number of papers published (5926 papers in total, accounting for 41.6% of the total number of papers published in this field in the past 10 years), occupying the core position in the international cooperation network, and the quality of papers published by European and American countries was relatively high; keyword cluster analysis has shown that the proton exchange membrane, catalyst, gas diffusion layer, membrane electrode, and cost of PEMFC were the current research focus. Therefore, the development trend of PEMFC key materials was analyzed in detail in this study. [ABSTRACT FROM AUTHOR]

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The flow field design plays a crucial role in the performance of proton exchange membrane fuel cells (PEMFCs). An efficient flow field design enhances electrochemical reactions in catalyst layers and facilitates the water removal process at the cathode. This study evaluates two PEMFC designs, rectangular and semicircle baffle flow fields, using computational fluid dynamics modeling. The models incorporate mass, heat and energy transport, electrode kinetics, and potential fields in PEMFCs. The research analyzes the hydrogen and oxygen mass flow rates and water distributions in PEMFCs at operating voltages of 0.3–1 V to determine the effect of the flow field design on performance. According to the results it is clear that flow field design has an important influence on PEMFC power density and performance. The calculated power density at 0.3 V and at 80°C for semicircle and rectangular baffle flow field PEMFCs respectively are 0.37 and 0.23 W cm−2, which indicates that PEMFC with semicircle baffle flow field has better performance in this study. [ABSTRACT FROM AUTHOR]

Optimizing the flow channel structures can improve the efficiency of proton exchange membrane fuel cells and promote the efficient utilization of clean energy. This study investigates the impacts of rectangular-baffle and tapered flow channels on electrical performance, temperature distribution and mass transfer of proton exchange membrane fuel cells, based on a 3D, multi-physical model. The equivalent average depth is adopted as the reference benchmark to mitigate the influence of channel depth. Results indicate that adopting variable-depth channels enhances convective mass transfer on the porous layer surface under higher voltage. The convective mass transfer of oxygen is dominant in the activation polarization region, while diffusion is dominant in the concentration polarization region. Variable-depth channels enhance heat and mass transfer in comparison to the straight channel. The tapered channel can improve the mass transfer flux in oxygen starvation region, and the drainage ability of the rectangular baffle channel is inferior to the tapered channel. The rectangular baffle channel demonstrates better convective heat transfer performance and temperature uniformity. A rectangular-baffle channel can increase net power by 4.31%, while a tapered channel can achieve a maximum increase of 9.27% when the pumping power is considered. Therefore, incorporating a tapered channel is an optimal strategy to boost cell efficiency. [ABSTRACT FROM AUTHOR]

This study employed Micro X-ray computed tomography (Micro-CT) to reconstruct the gas diffusion layer (GDL) in proton exchange membrane fuel cells (PEMFCs) and used lattice Boltzmann method (LBM) simulations to investigate the dynamic behavior of liquid water in the multiscale space of the GDL and gas channel (GC). The results showed that the transport of liquid water from GDL to GC through the interface of GDL-land and GDL-GC were divided into four stages: large pore filling, through-plane breakthrough, in-plane diffusion, and rapid transport into GC. The wettability of GC wall and GDL affects the transport and distribution of liquid water. When the contact angle on the GC wall was less than 90°, it promoted liquid water transport to the top GC wall, resulting in faster internal flow formation. Conversely, contact angles exceeding 90° caused liquid water to break through the GDL-GC interface from pores away from the GC wall. When the contact angle of the GDL was in the range of 110°–150°, both excessively large and excessively small contact angles hindered water transport and management. Maintaining the contact angle of the GDL around 130° enhanced the breakthrough path and transport speed of liquid water into the GC, and it also reduces localized liquid water accumulation. [Display omitted] • The real structure of GDL was reconstructed by Micro-CT scanning. • The dynamic behavior of liquid water in GDL-GC and their interface is studied by LBM. • The wettability of GC and GDL affects the transport and distribution of liquid water. [ABSTRACT FROM AUTHOR]

Hydrogen energy has been under close scrutiny by countries around the world. At present, the main technologies for utilizing hydrogen energy in transport power systems are hydrogen internal combustion engine (HICE) and proton exchange membrane fuel cell (PEMFC). Since both of them generate a large amount of waste heat, and waste heat recovery technology is one of the most promising means of utilizing waste heat to improve efficiency, this paper makes a comprehensive comparison of the two technologies in composite waste heat recovery (WHR) system in terms of modeled maximum efficiency, full operating condition efficiency and future predicted maximum efficiency. Based on the thermal efficiency analysis, the advantages, disadvantages, and development prospects of the two technologies in composite the WHR system are reevaluated. The results demonstrate that the efficiency of the HICE and PEMFC can be improved by 6.83% and 2.81%, with the use of WHR system, respectively. Under the full range of operating conditions, the HICE-WHR composite system has obvious efficiency advantage in middle-high load working condition, but PEMFC-WHR composite system has obvious efficiency advantage in low load working condition. Both of them will be very competitive and potential technology routes of hydrogen energy utilization for land transportation. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cell (PEMFC) parameter extraction is an important issue in modeling and control of renewable energies. The PEMFC problem's main objective is to estimate the optimal value of unknown parameters of the electrochemical model. The main objective function of the optimization problem is the sum of the square errors between the measured voltages and output voltages of the proposed electrochemical optimized model at various loading conditions. Natural rabbit survival strategies such as detour foraging and random hiding are influenced by Artificial rabbit optimization (ARO). Meanwhile, rabbit energy shrink is mimicked to control the smooth switching from detour foraging to random hiding. In this work, the ARO algorithm is proposed to find the parameters of PEMFC. The ARO performance is verified using experimental results obtained from conducting laboratory tests on the fuel cell test system (SCRIBNER 850e, LLC). The simulation results are assessed with four competitive algorithms: Grey Wolf Optimization Algorithm, Particle Swarm Optimizer, Salp Swarm Algorithm, and Sine Cosine Algorithm. The comparison aims to prove the superior performance of the proposed ARO compared with the other well-known competitive algorithms. [ABSTRACT FROM AUTHOR]

The structural tailoring of Pt‐based catalysts into 1D nanowires for oxygen reduction reactions (ORR) has been a focus of research. Mo(CO)6 is commonly used as a morphological modifier to form nanowires, but it is found that it inevitably leads to Mo doping. This doping introduces unique electrochemical signals not seen in other Pt‐based catalysts, which can directly reflect the stability of the catalyst. Through experiments, it is demonstrated that Mo doping is detrimental to ORR performance, and theoretical calculations have shown that Mo sites that are inherently inactive also poison the ORR activity of the surrounding Pt. Therefore, a novel gas‐assisted technique is proposed to replace Mo(CO)6 with CO, which forms ultrafine nanowires with an order of magnitude increase in length, ruling out the effect of Mo. The catalyst performs at 1.24 A mgPt−1, 7.45 times greater than Pt/C, demonstrating significant ORR mass activity, and a substantial improvement in stability. The proton exchange membrane fuel cell using this catalyst provides a higher power density (0.7 W cm−2). This study presents a new method for the preparation of ultra‐long nanowires, which opens up new avenues for future practical applications of low‐Pt catalysts in PEMFC. [ABSTRACT FROM AUTHOR]

Air inlet flow control is critical for performance of Proton Exchange Membrane Fuel Cells (PEMFC). An essential gauge for air input flow is the oxygen excess ratio (OER). However, accurate controlling for OER is a huge challenge because of the erroneous modeling, imprecise parameter values, and disturbances. An Active Disturbance Rejection Control (ADRC) approach is suggested in this research as a means of resolving the issue of fuel cells' internal and exterior interference. Firstly, the total disturbance is obtained using an extended state observer. Secondly, the total disturbance is compensated before the control action to determine the control quantity for air supply, which is further controlled by modifying the air compressor's voltage. The performance comparison between the suggested approach and PID and fuzzy PID control shows that the proposed technique can achieve a higher reliability for managing the mechanical faults of the air compressor. In addition, the root mean square error (RMSE) of control time and overshoot is smaller. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs) have been considered by many countries and enterprises because of their cleanness and efficiency. However, due to their high cost and low platinum utilization rate, the commercialization process of PEMFC is severely limited. The cathode catalyst layer (CCL) plays an important role in manipulating the performance and lifespan of PEMFCs, which makes them one of the most significant research focuses in this community. In the CCL, the intrinsic activity and stability of the catalysts determine the performance and lifetime of the catalyst layer. In this paper, the composition and working principle of the PEMFC and cathode catalyst layer are briefly introduced, focusing on Pt-based catalysts for oxygen reduction reactions (ORRs). The research progress of Pt-based catalysts in the past five years is particularly reviewed, mainly concentrating on the development status of emerging Pt-based catalysts which are popular in the current research field, including novel concepts like phase regulation (intermetallic alloys and high-entropy alloys), interface engineering (coupled low-Pt/Pt-free catalysts), and single-atom catalysts. Finally, the future research and development directions of Pt-based ORR catalysts are summarized and prospected. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles (UAVs) have become an integral part of modern life, serving both civilian and military applications across various sectors. However, existing power supply systems, such as batteries, often fail to provide stable, long-duration flights, limiting their applications. Previous studies have primarily focused on battery-based power, which offers limited flight endurance due to lower energy densities and higher system mass. Proton exchange membrane (PEM) fuel cells present a promising alternative, providing high power and efficiency without noise, vibrations, or greenhouse gas emissions. Due to hydrogen's high specific energy, which is substantially higher than that of combustion engines and battery-based alternatives, UAV operational time can be significantly extended. This paper investigates the potential of PEM fuel cells as an alternative power source for electric propulsion in UAVs. This study introduces an adaptive, fully functioning PEM fuel cell model, developed using a reduced-order modeling approach and optimized for UAV applications. This research demonstrates that PEM fuel cells can effectively double the flight endurance of UAVs compared to traditional battery systems, achieving energy densities of around 1700 Wh/kg versus 150–250 Wh/kg for batteries. Despite a slight increase in system mass, fuel cells enable significantly longer UAV operations. The scope of this study encompasses the comparison of battery-based and fuel cell-based propulsion systems in terms of power, mass, and flight endurance. This paper identifies the limitations and optimal applications for fuel cells, providing strong evidence for their use in UAVs where extended flight time and efficiency are critical. [ABSTRACT FROM AUTHOR]

The multi-cell coupling method is an effective way to solve the dynamic response problem of fuel cell power systems. However, it needs to control the stable output voltage to extend the service life of the power supply system. This article uses a PID controller to model and analyze proton exchange membrane fuel cells (PEMFCs). A lithium-sulfur battery (Li–S battery) model was established, and the discharge process of the lithium-sulfur battery was accurately simulated using the method of minimizing prediction error. These models are coupled through DC/DC boost converters to achieve a collaborative power supply system. The results indicate that the output voltage of the fuel cell is effectively stabilized at 24 V. The output voltage of the lithium-sulfur battery pack is designed to be 44–50 V. Each individual battery voltage is balanced to achieve a stable output voltage of 48 V. The system is powered by a proton exchange membrane fuel cell stack as the main power source and a lithium-sulfur battery pack as the auxiliary power source. At room temperature of 23 °C, the output voltage of the system can be stabilized within a controllable range of 48 V. Based on the operational characteristics and power demand analysis of the target ship, the basis for constructing a dual power source energy management strategy is elaborated. On this basis, fuzzy control was designed with ship demand power and lithium battery SOC as inputs and lithium battery output power as system output. An improved state flow controller was constructed by adding a ship demand power limiting unit to the logic threshold strategy that originally only had lithium battery SOC as the threshold. [ABSTRACT FROM AUTHOR]

Modifying the characteristics of the flow channel is essential to retard or prevent icing and improve the low-temperature operational performance of proton exchange membrane fuel cells (PEMFCs). This paper presents a two-dimensional transient mathematical model that investigates the influences of surface temperature, wettability, and volume size on the droplet icing process. The findings suggest that raising the surface temperature of the flow channel results in a longer droplet freezing time. Raising the surface temperature from 248.15 to 268.15 K can delay droplet freezing time by up to 62%. Increasing the surface contact angle from 78 to 150° can delay droplet freezing time by 45%. An increase in droplet volume can also prolong the time required for droplet freezing. Increasing the droplet volume size from 1 to 4 μL can delay the droplet freezing time by 35%. Moreover, the optimal parameters for maximizing the duration of droplet freezing are identified using response surface methodology. The corresponding conditions are found to be a surface temperature of 267.96 K, a surface contact angle of 134.08°, and a droplet volume of 3.29 μL. This work offers valuable guidance for enhancing the low-temperature performance of PEMFCs through flow channel design optimization. [ABSTRACT FROM AUTHOR]

As the fourth generation of stable power generation technology, proton exchange membrane fuel cell (PEMFC) has garnered extensive attention from both academia and industry in recent years. However, one of the primary impediments to the widespread commercialization lies in the service life. The aging of PEMFC systems under variable load conditions stands out as a prominent factor influencing their longevity. Consequently, delving into the aging mechanism and trend of PEMFC under variable load conditions assumes paramount significance in the quest for service life extension. This paper underscores a comprehensive exploration of the degradation mechanisms within various components of the membrane electrode assembly (MEA). Furthermore, it delves into the exploration of metrics capable of elucidating the health status of both the MEA and the overall PEMFC system. Meanwhile, this article pioneers an in-depth investigation into aging prediction methods predicated on diverse aging indicators, dissecting the efficacy and innovativeness of these strategies longitudinally. Ultimately, this article sets forth future research perspectives aimed at expediting the commercialization of power unit featuring integrated PEMFC systems. This review promises to furnish a deeper comprehension of the degradation mechanisms inherent to PEMFC, thereby enhancing their lifespan and reliability. [ABSTRACT FROM AUTHOR]

Traditional internal combustion engines (ICEs) have garnered considerable attention due to their high emissions and low efficiency issues. In this study, a novel ICE–fuel cell hybrid power system based on a single‐methanol fuel is proposed to address these concerns. The system utilizes methanol as fuel, directly supplying it to the methanol engine, and generates hydrogen for the fuel cell through methanol reforming technology. The structural design of the system fully exploits engine exhaust, first using waste heat for methanol reforming to produce hydrogen and then utilizing exhaust inertial potential energy to drive a dual turbocharging structure for air compression entering the fuel cell, thereby achieving self‐thermal balance. Thermodynamic analysis and cost evaluation indicate that the thermal efficiency of this system is improved by 8.34% compared to traditional diesel engine setups. Compared to engine‐fuel cell hybrid systems that do not utilize waste heat, the thermal efficiency is increased by 5.81%. In terms of economics, the cost of the methanol engine system is ≈.1466$ kW h−1$\left(\text{kW h}\right)^{- 1}$, which is 44.05% lower than the 0.262 $ kW h−1$\left(\text{ kW h}\right)^{- 1}$ fuel cost of traditional diesel engine systems. This study presents an innovative solution that significantly enhances thermal efficiency and offers economic advantages, providing a viable approach to address the low efficiency and high emissions issues of traditional ICEs. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs) have drawn much attention lately for their parameter extraction. It is important to carefully determine the optimal values of the uncertain parameters in the PEMFC model to guarantee accuracy and dependability. However, because of their nonlinearity and multi-variability, PEMFC modeling and optimization present a significant difficulty. Therefore, an improved atomic orbital search algorithm based on Lévy flight and chaotic maps, called CLAOS, was proposed in this study for the PEMFC parameter estimation problem, where the sum of square error was minimized. In order to test the effect of the Levy flight and chaotic maps on the performance of the Atomic Orbital Search (AOS) algorithm, ten different AOS variations were created and applied to solve the CEC2020 and CEC2022 benchmark problem suites. Their results were analyzed using Friedman and Wilcoxon tests, and the best variant was called the CLAOS algorithm. To validate the effectiveness of the proposed CLAOS, extensive simulations and performance evaluations were conducted on the PEMFCs model, where a 250W PEMFC stack was considered. Two search ranges for the unknown parameters and two operational conditions were considered. The performance of the proposed algorithm was compared with the six meta-heuristic search algorithms. Accordingly, the proposed algorithm achieved 4.722489 and 0.152027 for Case-1 and Case-2, respectively, which were the best objective function values among its rivals. Moreover, the results of the CLAOS algorithm were compared with the results reported in the literature for both cases. Accordingly, the CLAOS achieved the minimum error value compared to its rivals for both cases. To evaluate the performance of the algorithms statistically, the Friedman and Wilcoxon tests were applied to the results of the algorithms. The Friedman test results show that the proposed CLAOS algorithm ranked first with 1.1667 and 1.0000 score values for Case-1 and Case-2, respectively. All simulation and analysis results demonstrated that the proposed algorithm outperformed its rivals in solving the PEMFC parameter estimation problem.

Abstract The design of the reactant gas flow field structure in bipolar plates significantly influences the performance of proton exchange membrane fuel cells (PEMFCs). In this study, we introduced four innovative U-shaped flow field designs, namely: In-Out Multi-U, Out-In Multi-U, Distro In-Out Multi-U, and Distro Out-In Multi-U. To investigate the impact of these various flow fields on PEMFC performance, we conducted computational fluid dynamics (CFD) numerical simulations, validated through model experiments. Our results indicate that the Distro Out-In Multi-U flow field offers notable advantages compared to the conventional parallel flow field (CPFF) and conventional serpentine flow field (CSFF). These benefits include reduced inlet and outlet pressures, lower liquid water content, more uniform liquid water distribution, and a more even current density distribution. Furthermore, the Distro Out-In Multi-U design demonstrates improved efficiency, consuming less H2 (91.9%) than the CSFF while achieving a higher net power density output (10.1%). As a result, for the same power output, the Distro Out-In Multi-U utilizes only 83.5% of the H2 consumed by the CSFF. In summary, the U-shaped structured flow field exhibits superior output performance, enhanced energy efficiency, and improved resistance to flooding. These findings suggest that the U-shaped flow field design holds significant potential as a reactive flow field for PEMFCs.

Abstract Proton exchange membrane fuel cell (PEMFC) parameter extraction is an important issue in modeling and control of renewable energies. The PEMFC problem’s main objective is to estimate the optimal value of unknown parameters of the electrochemical model. The main objective function of the optimization problem is the sum of the square errors between the measured voltages and output voltages of the proposed electrochemical optimized model at various loading conditions. Natural rabbit survival strategies such as detour foraging and random hiding are influenced by Artificial rabbit optimization (ARO). Meanwhile, rabbit energy shrink is mimicked to control the smooth switching from detour foraging to random hiding. In this work, the ARO algorithm is proposed to find the parameters of PEMFC. The ARO performance is verified using experimental results obtained from conducting laboratory tests on the fuel cell test system (SCRIBNER 850e, LLC). The simulation results are assessed with four competitive algorithms: Grey Wolf Optimization Algorithm, Particle Swarm Optimizer, Salp Swarm Algorithm, and Sine Cosine Algorithm. The comparison aims to prove the superior performance of the proposed ARO compared with the other well-known competitive algorithms.

[Display omitted] • Basic principles and frontier progress of proton exchange membrane fuel cell catalysts are briefly introduced. • Low Pt content catalyst characteristics are analyzed. • Ordered intermetallic Pt-M alloy synthesis concept is described and interpreted. • Difficulty and improvement directions about ordered PtCo 3 are discussed. This review is devoted to the potential advantages of ordered alloy catalysts in proton exchange membrane fuel cells (PEMFCs), specifically focusing on the development of the low Pt content, high activity, and durability ordered PtCo 3 catalyst. Due to the sluggish oxygen reduction reaction (ORR) kinetics and poor durability, the overall performance of the fuel cell is affected, and its application and promotion are limited. To address this issue, researchers have explored various synthetic strategies, such as element doping, morphology adjusting, structure controlling, ordering and support/metal interaction enhancement. This article extensively discussed the Pt related ORR catalysts and follows an in-depth analysis of ordered PtCo 3. The introduction briefly discusses the direction of development of fuel cell catalysts and frontier progress, including theoretical mechanism, practical preparation, and Pt-containing electrode structures, etc. The subsequent chapter focuses on the Pt-Co catalyst, the evolution process of Pt alloy to Pt-Co alloy and the improvement scheme are introduced. The next chapter describes the properties of PtCo 3. Although the ordered PtCo 3 catalyst has a wide range of applicability due to low cost and high activity catalyst. However, besides the common agglomeration and sintering problems of Pt-Co alloy, its commercial application still faces unique problems of oversized crystal size, phase segregation, ordering transformation and transition metal dissolution. Therefore, in Chapter 4, this overview provides some possible improvement methods for three specific functions: crystal refinement, enhancing the effect of support and active substances, and anti-dissolution. [ABSTRACT FROM AUTHOR]

Hydrogen-powered fuel cells will play a vital role in the next generation of energy systems. In this regard, Proton Exchange Membrane Fuel Cells (PEMFC) represent a promising technical solution for all applications where direct electrification is not technically feasible or economically viable, such as the propulsion of heavy vehicles. However, robust production of high-quality fuel cell systems in scalable series production can only be achieved by an early assurance of the product quality considering the numerous variations on geometry element, part, and assembly level. This article presents the challenges and outlines the vision of a geometry assurance process capable of simulating the probabilistic assembly behavior of PEMFC stacks by multi-physics variation simulation, e.g., considering aspects of Finite Element Analysis and Computational Fluid Dynamics, under a realistic representation of the part manufacturing and assembly processes and their operation under variations. The findings reveal future research directions fostering the series production of robust, high-quality PEMFC stacks. [ABSTRACT FROM AUTHOR]

In response to the ongoing optimization of energy systems and the promotion of clean energy, this paper introduces a new high-efficiency cogeneration system based on proton exchange membrane fuel cells (PEMFC). Named the Transcritical Combined Cooling Heating and Power with Subcooling Coupled ORC (CPTSO) system, it undergoes energy, exergy, economic, and environmental (4E) assessments to evaluate its performance in both summer and winter modes. This paper also analyzes the effects of key factors on the new system's performance. The results indicate that the new system performs more effectively overall and achieves faster cost recovery during winter operations. With varying degrees of subcooling (ΔT subcooling), the system's average energy efficiency, fuel energy saving ratio (FESR), exergy efficiency, and pollutant reduction in winter are 60.97 %, 4.51 %, 17.16 %, and 33.35 % higher, respectively, than in summer. Changes in the main evaporation temperature (T e) result in winter improvements of 74.37 % in energy efficiency, 16.86 % in FESR, 17.6 % in exergy efficiency, and 45.5 % in pollutant reduction compared to summer. Similarly, adjustments to the outlet temperature of the gas cooler (T g) lead to winter increases of 56.75 % in energy efficiency, 0.49 % in FESR, 17.1 % in exergy efficiency, and 29.3 % in pollutant reduction over summer values. [ABSTRACT FROM AUTHOR]

Abstract Extending the operation of proton exchange membrane fuel cells (PEMFCs) at high temperature (i.e., 120 °C) and/or low relative humidity (

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 analyzes 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: membrane electrode assembly materials, bipolar plates and flow fields design, stack assembly, and cell control strategies. The challenges in the field and the prospects for the future are summarized and analyzed at the end. The aim of this work is to provide guidelines for improving the durability of PEMFCs in vehicle applications.

Analyzing degradation heterogeneity of proton exchange membrane fuel cell (PEMFC) while maintaining high practicality is consistently challenging, primarily due to the destructive and costly nature of existing techniques relying on material characterization. In this work, a designed magnetic array integrating 16 sensors within 25 cm2 space is used for direct scanning and imaging of PEMFC performance heterogeneity during its degradation. Results are validated through degradation mechanism analysis and material characterization, confirming its potential in guiding the development of durable materials. [ABSTRACT FROM AUTHOR]

The durability is a key factor of fuel cell in large-scale application of automobiles. It is great important to real the lifetime and health status of fuel cells, especially in vehicle driving conditions. Based on the experimental data, this paper used the model-based method and data-driven method to predict the life of fuel cells, respectively. The model-based method established the equivalent circuit model according to the mapping law of electrochemical impedance spectroscopy (EIS) and the parameters of the equivalent circuit model were identified by newly considering the phenomenon of voltage recovery, revealing the strong linear correlation between impedance and voltage. The data-driven method selected a combinatorial optimization PSO-LSSVM algorithm and compared it with the prediction results of MATLAB's time series toolbox. The results show the mean square error (MSE), End of Life (EOL) of the model-based method, the time series toolbox and PSO-LSSVM algorithm are 0.019, 8.2 × 10−3 and 4.42 × 10−5, the 260h, 438h and 427h, respectively. Comparing with the real EOL of 421h, the error of PSO-LSSVM algorithm is only 6 h, which means the remaining useful life can be predicted with high accurately. Thus this study provides a reference for fault identification and life prediction of fuel cell health management. • The equivalent circuit model is established to realize the segmented voltage prediction and analysis of fuel cells. • The MSE of combinatorial optimized algorithms PSO-LSSVM to predict voltage is only 4.42 × 10−5. • The method in paper provides a reference for fault identification and life prediction of PEMFC's health management. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) simulations have become a standard tool for logical interpretation of proton exchange membrane (PEM) performance. However, it has several parameters that affect the accuracy and reliability of results. Considering the most prevalent, we explore uncertainty analysis of chain configurations, thermostats, ensembles, and force fields for simulations of sulfonated poly ether ether ketone PEM. In order to choose proper chains and monomers number, total solubility parameter and density are evaluated. The mean square displacement of proton and temperature variances are determined, revealing the Berendsen thermostat as appropriate temperature controllers (11 Å2 and 9.478 K2, respectively). After choosing proper ensembles combination, COMPASSⅡ, COMPASSⅢ, and DREIDING force fields are compared, using glass transition temperature (Tg) and proton conductivity. Tg values of DRIEDING model (461 K) are in good agreement with experimental results (458 K), while conductivities of COMPASSⅢ model show better consistency (16.6 mS.cm-1 vs. 18.0 mS.cm-1). Therefore, parameters selection depends on the target simulation analysis. • Optimize the chains and monomers configuration of SPEEK polymer within PEMFC. • Proper thermostat/barostat methods selection via energy and temperature changes. • Determination of the suitable ensemble combination regarding to transport features. • Choosing forcefield types by evaluating mechanical and structural characteristics. • Employing novel approaches to assess T g and thermodynamic properties fluctuations. [ABSTRACT FROM AUTHOR]

Regenerative pumps are considered a promising option for hydrogen recirculation in proton exchange membrane fuel cell (PEMFC) systems. The geometry of the impeller exerts a direct influence on the pressurization process within the regenerative pumps. However, the influence has not been explored systematically in any available publications. This study investigates the effects of geometric parameters on pump performance and provides design guidelines for hydrogen regenerative pumps. A three-dimensional (3D) numerical model is developed and validated. The effects of critical geometric parameters, including the number of blades, impeller radius, and impeller radius ratio, on the performance of the regenerative pumps are then analyzed. Based on the analysis, this work recommends 35 blades and an impeller radius ratio of 0.65. To establish a correlation between operational performance and micro-flow mechanisms, the fluid velocity distribution at the interface of the rotating and stationary domains is quantitatively analyzed. Results indicate that a reduction in the flow rate results in increased axial velocity and decreased tangential velocity. The increased axial velocity enhances mass transfer, thus increasing the pressure and diminishing the efficiency, whereas the decreased tangential velocity intensifies the impact of the fluid on the blades, leading to increased shock losses and reduced efficiency. • The effects of the number of blades, impeller radius, and impeller radius ratio on the performance of hydrogen regenerative pumps are revealed. • The optimal values of the number of blades and impeller radius ratio are proposed. • The fluid flow velocities at the interface of rotating and stationary domains are quantitatively analyzed. • The flow mechanism of regenerative machines is elucidated through numerical methods. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs) offer high energy conversion rate and low pollution, while low durability of PEMFCs hinder the further development. Accurately predicting degradation trends and remaining useful life (RUL) are crucial to timely detecting problem and improving PEMFCs durability. In this paper, an enhanced transfer learning (Add-TL) based on adder network (AdderNet) and deep domain confusion is proposed for the prediction of PEMFCs. To reinforce the ability of extracting key features from extensive data, AdderNet with attention mechanism is applied. Furthermore, the fused deep domain confusion employs existing data to achieve higher prediction accuracy. The experimental results demonstrate that Add-TL outperforms other classical methods in predicting degradation trend, the optimal adjusted R-square (R2) values for the two datasets are 0.99879 and 0.99906, respectively. When Add-TL is applied to RUL prediction, the accuracy scores for two datasets reach 0.995, which further validating the applicability of Add-TL in PEMFCs prediction. • AdderNet applied for the first time to predict degradation trends and RUL of PEMFCs. • The method proposed in this paper integrates deep learning and transfer learning. • The incorporation of transfer learning the connections between data, aiming to improve the accuracy of RUL prediction. • Add-TL predicted static and dynamic conditions, providing a comprehensive validation. • Add-TL achieves best performance when training on datasets with varying lengths. [ABSTRACT FROM AUTHOR]