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Pt-based alloys, such as Pt3Ni, are among the best electrocatalysts for oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells. Doping of PtNi alloys with Zr was shown to enhance the durability of the operating ORR catalysts. Rationalizing these observations is hindered by the absence of atomic-level data for these tri-metallic materials, even when not exposed to the fuel cell operation conditions. This study aims at understanding structure–property relations in Zr-doped PtNi nanoparticles as a key to their ORR function. In particular, we calculated, using a method based on density functional theory, the most stable chemical orderings of pristine and Zr-doped Pt3Ni particles containing over 400 atoms. We thus clarify (i) preferential location and charge states of Zr atoms in the Pt3Ni NPs; (ii) effect of doping Zr atoms on the stability of the Pt skin of the Pt3Ni NPs; (iii) charge redistribution induced by Zr dopants; (iv) layer-by-layer atomic ordering in the Pt3Ni/Zr NPs with the increasing Zr content; and (v) effect of Zr atoms on the adsorption energies of O and OH species as indicators of the ORR activity. [ABSTRACT FROM AUTHOR]

Hydrogen (H2) combustion and solid oxide fuel cells (SOFCs) can potentially reduce aviation-produced greenhouse gas emissions compared to kerosene propulsion. This paper outlines a methodology for evaluating performance and emission tradeoffs when retrofitting conventional kerosene-powered aircraft with lower-emissionH2 combustion and SOFC hybrid alternatives. The proposed framework presents a constant-range approach for designing liquid hydrogen fuel tanks, considering insulation, sizing, center of gravity, and power constraints. A lifecycle assessment evaluates greenhouse gas emissions and contrail formation effects for carbon footprint mitigation, while a cost analysis examines retrofit implementation consequences. A Cessna Citation 560XLS+ case study shows a 5% mass decrease for H2 combustion and a 0.4% mass decrease for the SOFC hybrid, at the tradeoff of removing three passengers. The lifecycle analysis of green hydrogen in aviation reveals a significant reduction in CO2 emissions for H2 combustion and SOFC systems, except for natural-gas-produced H2 combustion, when compared to Jet-A fuel. However, this environmental benefit is contrasted by an increase in fuel cost per passenger-km for green H2 combustion and a rise for natural-gas-produced H2 SOFC compared to kerosene. The results suggest that retrofitting aircraft with alternative fuels could lower carbon emissions, noting the economic and passenger capacity tradeoffs.

Proton exchange membrane fuel cells (PEMFCs) hold immense promise for clean and efficient energy generation. However, controlling cold start at subfreezing temperatures remains a significant challenge that hinders their widespread commercialization, particularly in regions with harsh winters. Adaptive strategies dynamically adjust control parameters based on real-time operating conditions to optimize cold start performance, are regarded as powerful tools to overcome this hurdle. This paper reviews the state-of-the-art in PEMFCs cold start strategies, with a particular focus on adaptive approaches. This review delves into the complexities of cold start and explores various self-starting and assisted-starting methods that leverage adaptive approaches. An in-depth comparison of different adaptive strategies, including power optimization, temperature management, gas purging, control algorithm and oxygen starvation for cold start, are conducted comprehensively. The current research status is briefly outlined, highlighting potential areas for future inquiry. Toyota's breakthrough in rapid cold start achieved through adaptive strategies is analyzed. The critical gaps and limitations of these strategies are evaluated, future directions as well as suitable applications of different strategies are suggested. This work not only provides insights into the previous research progress, but also provides an outlook on future research directions of cold start techniques. • Adaptive strategies for cold start are reviewed and comprehensively compared. • Future directions and suitable applications of different strategies are suggested. • Toyota's breakthrough in rapid cold start achieved by adaptive strategy is analyzed. • Potential of cold start to meet energy efficiency, durability and cost is described. [ABSTRACT FROM AUTHOR]

Surface modification of metallic bipolar plates is a crucial subject for the performance elevation of proton exchange membrane fuel cells (PEMFCs). In this work, a series of CrN coatings and CrN/Nb coatings were prepared on SS316L by DC magnetron sputtering technology with different deposition power of 80 W, 100 W, 150 W and 200 W. The results show that with the decrease of deposition power, the surface of CrN/Nb coating changes from loose porous to uniform and dense, and the columnar crystal structure changes from burly to fine, which improves the corrosion resistance and electrical conductivity of the coating. The corrosion current density decreases from 3.5 μA cm−2 of CrN/Nb-200 W to 0.39 μA cm−2 of CrN/Nb-80 W. The XPS results show that the intensity of O–Cr peaks decreases while the intensity of N–Cr peaks increases with the decrease of power, which also confirms that the coatings prepared at low power have better corrosion resistance. Furthermore, the corrosion current density of CrN/Nb-80 W coated SS316L is 0.39 μA cm−2, and the interface contact resistance at 1.4 MPa is 9.2 mΩ cm2, which are much lower than those of CrN-80 W coated samples (1.58 μA cm−2 and 16.3 mΩ cm2). After the constant potential polarization test, the Fe and Cr ion concentrations in the solution of CrN/Nb coated specimens were significantly lower than those of CrN coated specimens, which indicates that the CrN/Nb coating has better corrosion resistance. The applying of Nb transition layer endows the coating and substrate better adhesion (increased 48%), which can hinder the penetrating cracks to the substrate in the coating and improve the corrosion resistance. • CrN and CrN/Nb coatings were deposited on the SS316L alloy under different powers. • The surface morphology becomes uniform and compact with decreasing the deposit power. • Coatings prepared at lower power possess better corrosion resistance and lower ICR. • The addition of Nb transition layer improves the performance of CrN coating. • Nb addition can hinder the columnar crystals growth of CrN. [ABSTRACT FROM AUTHOR]

To enhance the drainage performance of fuel cells under high load conditions, this study proposed a helical baffle flow field (FF). This FF is based on a semi-circular cross-section design and generated along a helical trajectory, with four structural parameters (pitch, radius, gap, and shear angle). To optimize the drainage performance of the novel FF, a multi-objective optimization framework is established with four structural parameters as the design variables and pressure drop in the gas flow channel and water coverage ratio on the gas diffusion layer surface as the optimization objectives. The optimization process is divided into three steps: First, initial sample data is collected through experimental design, and the simulation model considered the coupled effects of multi-channels, dynamic contact angle effects of liquid droplets in high-speed motion, and linked the inlet gas and water velocities with the operating current density to enhance the simulation accuracy. Second, artificial neural network surrogate models are trained based on the obtained simulation data to establish a high-precision mapping relationship between the performance indicators and the design variables and ensure good generalization ability. Finally, based on the surrogate models, the multi-objective optimization is carried out using genetic algorithms to generate the Pareto front, and the optimal FF structure parameter combination is obtained. The research results show that the optimized FF structure improves the comprehensive drainage performance by 7.8%. Among them, the diameter of the baffle has the greatest impact on the drainage performance, while the shear angle has the least impact. This study provides a new perspective for optimizing the drainage performance of fuel cells under high load conditions. • Water management strategies in dual channel structures with GDL are explored. • Physical and surrogate models combination increases the efficiency of optimization. • The baffle structures with helical track accelerate the liquid removal. • Investigated the mechanism of the under-rib mass transfer effects on droplet motion. [ABSTRACT FROM AUTHOR]

This study presents the design, construction, and evaluation of a hybrid renewable energy system integrating a wind turbine, proton exchange membrane electrolyzer, and proton exchange membrane fuel cell. The system efficiently converts excess wind power into hydrogen during off-peak hours and utilizes stored hydrogen for electricity generation during peak demand. Laboratory experiments optimized the proton exchange membrane electrolyzer and proton exchange membrane fuel cell, achieving maximum hydrogen production of 55 mL/min at 5 V and a peak fuel cell power output of 1.877 W at 50 °C. Simulation results demonstrated the hybrid renewable energy system's ability to deliver reliable power at an energy cost of $0.6342/kWh under optimal conditions. Two scenarios were analyzed: (1) wind turbine and fuel cell operating concurrently and (2) wind turbine supplying the electrolyzer and fuel cell meeting the load independently. Scenario 1 proved more cost-effective, with the wind turbine generating 660 kW and the fuel cell 200 kW. This research highlights the potential of hybrid renewable energy systems to address energy demand challenges, reduce costs, and improve sustainability, providing practical solutions for off-grid applications. [Display omitted] • Wind/Hydrogen/Fuel Cell system effectively meets energy needs in Koohin region. • PEMELZ performed best with 0.5 M Sulfuric acid as the electrolyte. • FC achieved peak performance with preheated inlet air at 50 °C. • Maximum HYP was 5.4 L/h in the optimized system. • Energy cost was 0.6342 $/kWh when WT and FC worked simultaneously. [ABSTRACT FROM AUTHOR]

This paper focuses on the determinants of establishing dominant hydrogen fuel cell technology designs in the maritime industry in Western Europe. By systematically studying the battle between the Solid Oxide Fuel Cell and the Proton Exchange Membrane Fuel Cell, utilizing the best-worst method it arrives at importance for factors for design dominance. It appears that 'fuel cell costs' is the most important factor: it received a global average weight of 0.18. This is the first time that factors for design dominance are studied in the maritime industry and the paper offers novel empirical material from a distinct sector. It also provides a first indication that the Solid Oxide Fuel Cell will have the highest chance to become the dominant design although the Proton Exchange Membrane Fuel cell is a close follower. The paper discusses contributions, implications, and future research recommendations for the literature on dominant designs. • This paper studies factors for hydrogen fuel cell technology design dominance. • Two technologies are compared in a systematic way using the best worst method. • Fuel Cell Costs was seen as most important receiving a global average weight of 0.18. • Solid Oxide Fuel Cell has the highest chance to dominate closely followed by PEMFC. [ABSTRACT FROM AUTHOR]

In this study, we focus on modeling the dynamic system of a fuel cell hybrid vehicle, particularly the stack, to enhance hydrogen utilization efficiency through an adapted energy management control strategy. The fuel cell system is modeled for each balance of plant (BOP) component. In the modeling of the stack, it was designed to enable the calculation of water behavior inside gas diffusion layer. After modeling this vehicle system, we tested three different driving strategies across five driving cycles: HWFET, FTP-75, UDDS, NEDC, and WLTP. The strategies explored were constant power, baseline, and target State of Charge (SOC) change. Our findings reveal that the target SOC change strategy resulted in the lowest hydrogen consumption, with minimal variation in battery SOC at the beginning and end of the drive. Specifically, this strategy led to a hydrogen consumption reduction of approximately 24% in low-load conditions (FTP-75, UDDS, NEDC) and 10% in high-load conditions (HWFET, WLTP). • Dynamic model of fuel cell system is applied for accurate simulation of fuel cell vehicle system. • New target SOC change method proposed and compared with other EMS methods. • Target SOC method minimizes hydrogen use across simulations in five drive cycles. [ABSTRACT FROM AUTHOR]

In order to increase the overall efficiency of the Polymer Electrolyte Membrane (PEM) fuel cell system the recirculation of excess hydrogen from the fuel cell outlet to the inlet can be conducted by a passive hydrogen ejector instead of an electric hydrogen pump. The disadvantage of a hydrogen ejector with a fixed layout is that it does not cover the necessary range of the fuel cell operating conditions from low to high power. Therefore, in this study a new approach for thoroughly analyzing the influence of variable geometric parameters on the recirculation performance of the passive hydrogen ejector is investigated by Computational Fluid Dynamics (CFD) simulations. Based on a sensitivity analysis the nozzle radius has been identified as geometric parameters which has the largest effect on the mass flow and mass flow ratio. A moving needle concept has been selected as most suitable to vary the nozzle cross section. Compared to a passive recirculation unit with a fixed ejector geometry for a fuel cell operation limited to 100 kW the needle concept allows an operation from 17 kW to 100 kW of fuel cell power. An additional optimization with a two-step needle can further reduce the sensitivity of the fuel cell pressure drop from 50 mbar to 70 mbar on the necessary mass flow at low fuel cell power. System simulations of the hydrogen ejector confirm that the variable recirculation unit can be operated also under dynamic operation of the fuel cell system by maintaining the necessary mass flow and mass flow ratio. • A concept for a variable passive hydrogen recirculation unit is developed. • Influence of ejector geometries on recirculation characteristics is evaluated. • Variable recirculation unit maintains required stoichiometry ratios. [ABSTRACT FROM AUTHOR]

This study investigated the development of chopped carbon fiber (CCF)‐reinforced epoxy (EP)/graphite (G) composite bipolar plates (BPs) using a one‐step compression molding process. The primary objective was to fabricate CCF‐reinforced EP/G BPs to enhance their electrical conductivity performance by evaluating the electrical conductivity and compactness of the plate among expanded graphite (EG), carbon black (CB) Vulcan, a combination of EG and CB Vulcan, and CB Ensaco. The results indicated that the EG exhibited the highest electrical conductivity of 9.3 S cm−1 and compactness due to the low surface area. Consequently, CCF‐reinforced EP/G/EG was selected for further optimization using response surface methodology (RSM) to analyze the parameters of EG composition, CCF composition, and temperature for optimizing electrical conductivity and porosity. The optimum conductivity and porosity of the CCF‐reinforced EP/G/EG reached 22.7 S cm−1 and 9.84% with EG composition, CCF composition, and temperature of 7.56 wt.%, 6.63 wt.%, and 186°C, respectively. After optimization, EP/G/EG was connected to a circuit to light up a bulb. It showed a substantial improvement in illumination compared with the samples before optimization. Therefore, the use of CCF‐reinforced EP/G/EG with one‐step compression molding has proven highly successful for converting energy in renewable energy applications, showcasing exceptional performance. [ABSTRACT FROM AUTHOR]

Fuel cell heavy-duty trucks (FCHDTs) are pivotal for achieving carbon emission reductions in the transportation sector, with energy flow distribution and transient characteristics critical to their overall efficiency. This study presents comprehensive energy flow tests on an FCHDT under various operating conditions, providing a detailed analysis of energy distribution and subcomponent behavior. Results demonstrate significant variations in hydrogen consumption, battery charging/discharging and mechanical energy recovery patterns across different driving cycles. During transient conditions, hydrogen consumption frequently fluctuates with changes in vehicle speed and power demand, while battery state of charge (SOC) is affected by multiple factors and shows no direct correlation with hydrogen consumption. Proton Exchange Membrane Fuel Cell (PEMFC) efficiency declines with increasing power output due to reduced electrochemical reaction efficiency from intensified mass and heat transfer limitations, and brake energy recovery is found to be crucial for capturing and converting kinetic energy into electrical energy, particularly on complex terrains or under heavy loads. These findings provide valuable insights and guidance for the development of high-performance FCHDTs. [Display omitted] • Energy flow tests of FCHDT were conducted across different driving cycles. • Energy flow distribution and transient characteristics were thoroughly analyzed. • FCS efficiency declines with higher output power due to lower electrochemical efficiency. • Brake energy recovery plays a dominant role in vehicle operation under heavy loads. [ABSTRACT FROM AUTHOR]

Aqueous-phase reforming of methanol (APRM) is essential for the application of polymer electrolyte membrane fuel cells (PEMFCs) that utilize hydrogen as fuel. The development of highly active catalysts with low CO selectivity is crucial to addressing this challenge. This paper presents a novel high-activity APRM catalyst, Pt/Fe 5 C 2 @C, composed of Fe 5 C 2 nanoparticles encapsulated in graphite carbon layers (Fe 5 C 2 @C) along with loaded Pt. Both XPS and TEM confirm the presence of strong metal-support interaction (SMSI) between Pt and Fe 5 C 2 @C. This SMSI not only enhances the dispersion of Pt on the Fe 5 C 2 @C surface but also changed the electron density of the loaded Pt, thereby maximizing the active sites. Consequently, the Pt–Fe 5 C 2 interface in Pt/Fe 5 C 2 @C effectively activates methanol molecules, promoting the water-gas shift reaction on the catalyst surface, resulting in excellent hydrogen production activity and extremely low CO selectivity. Specifically, the hydrogen production rate of the 11%Pt/Fe 5 C 2 @C catalyst reached 139.9 mmol g−1 h−1, which is significantly higher than that of other common Mo-based oxides and Mo-based carbide catalysts, with a CO selectivity as low as 0.01%, achieving almost CO-free hydrogen production. This finding offers a promising pathway for CO-free hydrogen production via the APRM reaction. • Carbon-coated Fe 5 C 2 (Fe 5 C 2 @C) was successfully prepared. • Strong metal-support interaction was observed between Pt and Fe 5 C 2 in Pt/Fe 5 C 2 @C. • Pt/Fe 5 C 2 @C exhibited extremely low CO selectivity in the APRM reaction. • Pt/Fe 5 C 2 @C demonstrated a high hydrogen production rate in the APRM reaction. [ABSTRACT FROM AUTHOR]

The proton exchange membrane integrity can be compromised during hot-press fabrication of membrane electrode assemblies (MEAs) causing premature cell failures during operation. In this work, infrared (IR) thermography was used as a diagnostic tool to spatially visualize hydrogen (H 2) crossover and identify process-induced-membrane irregularities (PIMs). These irregularities were identified as seed locations for MEA failures. Fine tuning of hot-press conditions was used to mitigate premature cell failures informed by accelerated stress testing (AST). The impact of PIMs on the initial performance, high-frequency resistances, open-circuit voltage, and H 2 crossover are reported. Nafion XL and 212 membranes, hot-pressed with a force of 16 kg/cm2 and temperature of 120 °C, were found to be consistently irregularity-free. Irregularity-free MEAs using Nafion 211, 212, and XL membranes demonstrated AST lifetime improvements of 58, 64 and 400%, respectively, compared to those fabricated with non-optimized conditions. This work highlights the importance of fabrication parameters on premature cell failures. • Process-induced membrane irregularities are seed locations for MEA failure. • Mitigated early onset failures through optimization of hot-press conditions. • Trade-offs between performance and durability are dependent on hot-press conditions. • IR thermography enabled correlation of failures to hot-press conditions. • Isolated material properties that influence durability from fabrication parameters. [ABSTRACT FROM AUTHOR]

Purging is widely used in controlling water content during cold starts. High-frequency resistance (HFR) is one of the main methods used to characterize the water state in membrane electrode assemblies (MEA). However, it is difficult to accurately determine the water content inside the fuel cell at shutdown using the HFR alone. Thus, in this study, a method for characterizing the water state of MEA based on the distribution of relaxation times polarization resistance was established. Based on the experiment, the water content variation in each component during shutdown purge was analyzed. Finally, the influence of operating parameters during shutdown purge on the water content was analyzed, showing that purge efficiency in Stage 1 increased with the purge flow rate. While in Stage 2, it was influenced by the coupled effects of temperature and flow rate. Moreover, low relative humidity significantly improved the purge efficiency in Stages 1 and 2. • A method was devised to identify water state in MEA during shutdown purge with load. • Changes in water content of components during shutdown purge were tracked with EIS. • Water state of components during purging process forms three distinct stages. • Flow rates, temperatures, loading currents, and RH affect water state changes. [ABSTRACT FROM AUTHOR]

Polymer electrolyte membrane (PEM) fuel cells employing a Pt catalyst layer composed of stacked Pt nanoparticles deposited by pulsed laser deposition (PLD) has the advantage of high Pt utilization and large surface-to-volume ratio so as to render a high mass-specific power density. However, the current density and cell durability are limited by the restricted gas permeability in the catalyst layer and electrochemical Ostwald ripening respectively. Here we demonstrate that by adding a nanoporous CeO 2 overlayer produced with PLD together with drop-casted Nafion dried under optimized temperature and relative humidity, the current density and durability of the cell can be enhanced substantially relative to that without CeO 2 layer and using a commercial PEM, presumably through controlling Nafion distribution in the pores of the Pt layer. This method is expected to be also applicable to all PEMFCs based on nanostructured thin-film catalyst with catalyst support. • Porous CeO 2 layer consisting of stacked CeO 2 nanoparticles is deposited by PLD. • CeO 2 layer moderates infiltration of Nafion into catalyst layer and scavenges ROS. • Drying Nafion at optimal temperature and humidity improves microstructure. • Combination of CeO 2 layer and drop-casted Nafion raises cell current and durability. [ABSTRACT FROM AUTHOR]

The durability issue is the primary factor affecting the life and cost of Polymer Electrolyte Membrane Fuel Cell (PEMFC). This paper presents a novel State of health (SOH) prognosis method for PEMFC in different conditions using Principal Component Analysis (PCA) and Gaussian Process Regression (GPR). Firstly, the robust locally weighted smoothing method is used to preprocess the recorded PEMFC operation data for filtering measurement errors. Then, PCA is applied to extract the principal components of the time series of original multi-dimensional input variables for PEMFC, eliminating the correlation between the original variables and reducing the dimensionality of input variables. Finally, the degradation prognosis and Remaining Useful Life (RUL) prognosis are made by GPR. Two degradation experiments for PEMFC verify the proposed method in different conditions. The test result shows that PCA can effectively reduce the dimensionality of PEMFC operating conditions. Compared with traditional methods, PCA-GPR has higher SOH prognosis accuracy. PCA-GPR provides a 462-h RUL prognosis on a life duration of 1150 h, which is sufficient for maintaining the PEMFC. • PEMFC operating variables are reconstructed by the principal component analysis. • PEMFC degradation prognosis model is established by Gaussian process regression. • The proposed method provides a higher degradation prognosis accuracy for PEMFC. • Proposed method makes a long remaining useful life prognosis for PEMFC. [ABSTRACT FROM AUTHOR]

In recent years, proton exchange membrane fuel cells (PEMFC) have progressed towards commercialization. However, non-uniform current distribution, which affects efficiency and lifespan, remains a significant issue. Traditional current distribution tests fail to pinpoint the cause of this non-uniformity. In this work, localised electrochemical impedance spectroscopy (EIS), based on printed circuit board (PCB), was employed to uncover the reasons. Results indicate that oxygen reduction reaction resistance can't reflect current distribution solely due to the influence of double-layer capacitor, and the oxygen diffusion resistance can achieve this goal. With the decrease of membrane thickness, the distribution of current density becomes more uniform due to the more uniform oxygen reduction reaction resistance. The PEMFC with a thinner membrane achieves lower membrane resistance more easily, making higher drainage capacity crucial for it. Therefore, PEMFCs with thinner membranes require lower humidity to maintain performance and uniformity. • In-situ investigation of in-plane variations in PEMFC using localised EIS. • Utilized localised EIS to determine the distribution of PEMFC parameters. • Analysed current distribution mechanisms in PEMFC with localised EIS. • Studied the impact of membrane thickness on EIS parameter distribution. [ABSTRACT FROM AUTHOR]

Electrochemical energy conversion technologies include proton exchange membrane fuel cells (PEMFCs) where proton interchange is an alternative to diesel distributed generation, and PEMFCs are considered as a promising backup power source and a tool to regulate power consumption. Some of the major benefits of these PEMFCs especially in power system applications include low emission of carbon, fast load following capability, no noise and high start-up reliability. It is challenging to find the best PEMFC parameters because the model is complex and the problem is nonlinear; not all optimization algorithms can solve this problem. This paper presents a new approach that applies QUasi-Affine TRansformation Evolution algorithm with a new adaptation of Evolution Matrix and Selection operation (QUATRE-EMS) to determine optimal values of uncertain parameters in PEMFC stack references. The objective function of the optimization problem is defined as the sum of squared errors of the actual and predicted voltage data. The effectiveness of the proposed QUATRE-EMS algorithm is also checked through statistical analysis and the QUATRE-EMS variant is compared with other variants of DE optimization algorithms which are recently proposed in the state-of-the-art literature such as LSHADE, MadDE, CS-DE, LPalmDE, EDEV, jSO, SHADE, ISDE, and JADE. Results show that the QUATRE-EMS algorithm reduces SSE significantly, with an average SSE of 0.078492, which is 15% less than the best performing existing algorithms. QUATRE-EMS also achieved the lowest average values of absolute error, relative error and mean bias error among different PEMFC stack references, with accuracy improved by up to 20%. It was also computationally more efficient, cutting runtime in half compared to other methods. The results of these findings confirm the effectiveness and practicability of the QUATRE-EMS algorithm for improving the accuracy of BCS500W, NedStackPS6, SR12, H12, HORIZON, and Standard 250W PEMFC stack references. [ABSTRACT FROM AUTHOR]

In the catalytic layer of proton exchange membrane fuel cells, water molecules in ionomers tend to be accumulated at the ionomer/Pt interface, preventing oxygen from reaching the Pt surface to participate in chemical reactions. It is necessary to take measures to improve the water molecules distribution and proton transport performance in the ionomer on the Pt surface. In this work, the effect of "acid–base pair" functionalized graphene oxide (AB‐GO) as the additive on the distribution of water molecules and transport property in the ionomer is evaluated. The results demonstrate that with the addition of AB‐GO, the distribution uniformity of water molecules and hydronium ions in the ionomer on the Pt surface is improved. The connectivity of water cluster is also increased. When the doping ratio of BAF‐GO and TF‐GO is 1:3, the connectivity coefficient of water cluster is about 1.37 times that of Nafion ionomer without the doping. [ABSTRACT FROM AUTHOR]

During an aging test of a high temperature proton exchange membrane fuel cell (HT-PEMFC) without exhaust pressure control loop, the anode and cathode pressures are dependent on variations in gas flow and atmospheric pressure. The voltage degradation rate is then impacted by atmospheric pressure variations. To extract the aging rate independently of the pressure, a possible solution is to estimate the voltage variation at a given pressure change. In this work, this voltage/pressure sensitivity was estimated in post-processing, by fitting regression planes (on measured voltage data) in the three dimensions: voltage, pressure, and time. It was applied on an aging test of 2753 h at 160 °C, at ambient pressure and at different constant currents (0.2, 0.4, and 0.6 A/cm2) which was carried out on an Advent Technologies Inc. PBI MEA of 45 cm2 active surface. The impact of varying atmospheric pressure on the calculation of degradation rates is then discussed and compared with another method developed in a previous work. It was found that a variation of 6 mV (2.4 % of initial voltage) at 1 A/cm2 during an aging test can be attributed to pressure variation alone, and not to cell degradation. Furthermore, it was observed that the voltage/pressure sensitivity is different depending on the period analyzed, at identical operating conditions (which would indicate that the dependence on pressure varies during aging). Indeed, at 0.2 A/cm2, the voltage response to a variation in pressure was quantified at approximately 50 μV/mbar and 80 μV/mbar at the start and end of life respectively. This method could therefore be used as an on-line diagnostic tool to monitor the fuel cell state of health. [Display omitted] • Aging test of a high temperature proton exchange membrane fuel cell for 2753 h. • Model of the impact of pressure and time on cell voltage. • Obtaining coefficients of the voltage variation against pressure and time. • Degradation rate can significantly be impacted by pressure variations only. • Method for post processing aging tests to correct the voltages against pressure. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs) operate with various parametric values, among which temperature, pressure, and flow rate are the most prominent. The effects of these parameters on the current density of PEMFCs and their interactions with each other are important. This study performed a comprehensive parametric evaluation. For this purpose, PEMFC stack simulation was conducted, and the effects of parameters on current density were determined. Various machine learning (ML) methods were applied to the obtained results, and regression analysis was performed. Current density was considered the output, and operating temperature, fuel flow rate, air flow rate, and fuel supply pressure were regarded as inputs. In total, 24 ML methods were applied, and 6 of them yielded excellent results. The six ML methods were the fine tree model, multilinear regression, cubic support vector machine, the bagged tree model, bilayered neural network, and rational quadratic Gaussian process regression (GPR). The regression coefficient (R2), mean absolute error, mean square error, and root mean square error of each model were derived. Results indicated that rational quadratic GPR and bilayered neural network were the most effective among all the methods. The R2 values of the rational quadratic GPR and bilayered neural network models were equal to 1, indicating a perfect match between the predicted and observed values. [ABSTRACT FROM AUTHOR]

Low-temperature purge significantly impacts the performance of Proton Exchange Membrane Fuel Cell (PEMFC) under cold start condition. To explore the influence of gas blowing on PEMFC at low temperature, first of all, a three-dimensional and multiphase-physical model for a single cell is established. Secondly, the performance impacts of two factors, the water content in proton exchange membrane and the ambient temperature, on PEMFC are analyzed. Then, the influences of gas flow rate, blowing time and gas temperature on water content in membrane are conducted. The results indicate that a higher initial water content in the membrane at a lower start-up temperature shortens the duration of the cold start process. Consequently, it leads to increase cold starting failures. As the gas flow rate increases, the water content in the membrane decreases as the change rate decreases. The water content can be reduced by extending the purging time, but beyond a certain threshold no significant change is observed. Furthermore, the purge gas temperature shows minimal impact on the rate of change of water content. However, as it increases, the water content decreases. In order to balance both the purging effect and energy consumption, the purging flow rate of 1x10-5 kg.s-1 and the purging time of 56 seconds are recommended. [ABSTRACT FROM AUTHOR]

The low surface area carbon black (Regal 330) underwent heat treatment in a nitrogen environment at varying temperatures (1000, 1200, 1400, and 1500 °C). Both original and heat-treated Regal carbon blacks served as support material for the platinum (Pt) catalyst in the polymer electrolyte membrane (PEM) fuel cell. Comprehensive physical and chemical characterizations of carbon blacks and Pt catalysts were performed using BET, FTIR, Raman spectroscopy, XRD, SEM, TEM, XPS (C 1s), ICP-MS, zeta potential, contact angle, and 3D topography analyses. The catalysts were characterized electrochemically using a three-electrode system and a PEM fuel cell testing station. For the oxygen reduction reaction (ORR), the Pt/R-14 showed a limiting diffusion current density of 2.827 mA cm−2 (@1600 rpm). The PEM fuel cell testing station yields the best results with the same catalyst. At 0.6 V and 0.1 V retention potentials, Pt/R-14's current and power density values (@0.6 V) were 537.0 mA cm−2 and 321.1 mW cm−2 and 642.6 mA cm−2 and 384.3 mW cm−2, respectively. The results of heat-treated Regal carbon blacks were superior to those of the original case. This study uniquely applies Regal carbon black and its heat-treated forms to a PEM fuel cell as catalyst support material. [ABSTRACT FROM AUTHOR]

Summary: Due to the low output voltage and soft output characteristics of proton exchange membrane fuel cell (PEMFC), DC/DC converter with high voltage gain has become a key part for safe and stable operation. In this paper, a novel high step‐up DC/DC converter with switched‐inductor (SI), switched‐capacitor (SC), and a capacitor‐clamped double‐switch structure is proposed, which can obtain high voltage gain with lower duty cycle and low voltage stress on switches and diodes. Switches run in an interleaving mode to reduce the inductor current ripple. The detailed analysis of the converter, device parameter design, comparation with other converters, and double closed‐loop controller design are presented, respectively. Finally, a 100‐W, 15‐V/100‐V experimental prototype is built to demonstrate the effectiveness of the proposed converter and controller. [ABSTRACT FROM AUTHOR]

Fuel cells contribute to decentralized and individually controllable energy supply. The low-temperature polymer electrolyte membrane fuel cell is ideal for both stationary and mobile use due to its low operating temperatures and superiority in discontinuous operation. Thermoplastics can be used as materials for bipolar halfplates, which have the advantage of low-cost manufacturing processes, as the components do not require cost-intensive post-processing due to their excellent corrosion resistance and electrical contacting. But the environmental conditions in operation pose a great challenge to the materials to be used: permanent humidity and sulphuric acid environment at 85°C, high required electrical conductivity and hydrogen impermeability. In order to demonstrate the potential of bio-based materials, adhesives for both sealing and conductive bonding of all joints within a fully bonded fuel cell are being developed and tested in an ongoing project. The epoxy resin systems developed can be both, one and two-component, and have different proportions of sustainable carbon. In addition, the fuel cell components, also consist of sustainable raw materials, so that bonding surfaces also pose a challenge. Results on the lap shear strength of the developed adhesives as well as on the durability of the adhesives under fuel cell environment are presented. Initial functional tests on bipolar plates bonded with proportionally bio-based raw materials show a functionality comparable to that of petroleum-based raw materials for epoxy adhesives. [ABSTRACT FROM AUTHOR]

The flow distribution issue is of significance to the fuel cell stack performance and durability, which herein is studied from a theoretical and practical level. The manifold flow fundamentals are clarified and the pressure‐reconstruction‐based principle to regulate flow distribution is revealed. The prerequisite and corequisite lie in the ratio of pressure drop between headers and the entire manifold, and the pressure recovery in the inlet header. Accordingly, a step‐by‐step manifold design methodology is proposed and further quantified by detailed and organized simulations. A desirable effect on flow uniformity is validated in large‐scale stacks consisting of 300 and 400 cells, and the values of flow uniformity index represented by coefficient of variation (CV) are 3.32% and 2.95%, respectively. Moreover, a novel wedge‐shaped layout of the intake header is proposed for further optimization. The corresponding CV values have notably declined to 1.36% and 1.29%, nearly 60% lower than the conventional rectangular counterparts. [ABSTRACT FROM AUTHOR]

In the operation of the proton exchange membrane fuel cell (PEMFC) with dead-ended anode (DEA), the cathode relative humidity affects the accumulation state of water and nitrogen on the anode side, which in turn seriously affects the cell's working performance. In order to investigate the mechanism of the cathode relative humidity on the PEMFC performance, numerical simulation and segmented in-situ measurement methods were used in this study. The results of the study showed that the lower cathode relative humidity causes insufficient water content in the PEMFC. This can further lead to localized dehydration of the membrane, which causes degradation of the DEA-PEMFC performance. Moreover, the higher cathode relative humidity increases the water content on the cathode side of the PEMFC. This not only increases the membrane permeability to nitrogen but also accelerates the water concentration back-diffusion process. The water and nitrogen that penetrate into the anode side can occupy the gas transport channel and hinder hydrogen transport, resulting in the insufficient localized gas supply in the DEA-PEMFC. This finally results in lower transient voltages and significantly shorter stabilized operation times. Therefore, reasonable control of cathode relative humidity is required to ensure long-term efficient and stable operation of the DEA-PEMFC. [ABSTRACT FROM AUTHOR]

Dead-ended proton exchange membrane fuel cells (PEMFCs) using pure hydrogen and oxygen can improve fuel efficiency and cell performance, making them widely applicable in enclosed spaces. However, dead-ended PEMFCs are prone to flooding, which reduces cell performance and service life. To address this issue, an oxygen recirculation system utilizing oscillating flow generated by pressure differences is designed in this study. This system not only achieves close to 100% fuel utilization but also optimizes water management and enhances current density uniformity. The optimal oxygen cycling conditions were selected based on current density uniformity and cell performance enhancement. The results show that a larger pressure difference amplitude improves water removal from the cell; however, excessively large pressure differences can lead to unstable cell operation. The oscillating flow generated by pressure differences significantly improved current density uniformity, particularly at higher output load currents. Current density uniformity improved by 16.29% at a current of 75 A. The experiment demonstrates that the best current density uniformity is achieved when managing water using a pressure difference at 4-minute intervals, as longer or shorter oscillation intervals are unsuitable for dead-ended performance. [ABSTRACT FROM AUTHOR]

Hydrogen fuel cells are vital for green energy to replace traditional energy. However, their lifetime is an important factor limiting their development. In this study, commercial materials were used to prepare proton exchange membrane fuel cells (PEMFCs), and pure oxygen was used as the cathode gas to accelerate their lifetime evaluation. The components of the membrane electrode assembly were characterized, and significant thinning was observed in the local proton exchange membrane (PEM). Therefore, the uniformity of the internal conditions of the fuel cell is the key to ensure a long lifetime. The hydrophilicity of the gas diffusion layers increased as the carbon disorder increased via the adsorption of hydrophilic chain segments produced by PEM degradation. The growth of platinum particles in the catalyst layer reduced the electrochemical active area of the catalyst, but the reduction rate slowed and then stabilized. This study of the lifetime of PEMFCs and changing properties of commercial materials clarifies the existing problems of fuel cells and contributes to the development of long-life fuel cells. [ABSTRACT FROM AUTHOR]

The increasing concern about global warming and the depletion of fossil fuel reserves has led to a growing interest in alternative energy sources, particularly fuel cells (FCs). These green energy sources convert chemical energy into electrical energy, offering advantages such as quick initiation, high power density, and efficient operation at low temperatures. However, the performance of FCs is influenced by changes in operating temperature, and optimal efficiency is achieved by operating them at their maximum power point (MPP). This study uses Proton Exchange Membrane Fuel Cells (PEMFCs) to charge electric vehicles (EVs), amplifying the voltage generated by the FC using the Interleaved Boost-Cuk (IBC) converter. The optimal tracking of the maximum power output is achieved using the Improved Mayfly optimized (IMO) Cascaded Adaptive Neuro Fuzzy Inference System (Cascaded ANFIS). The study uses MATLAB to simulate the task in various settings and analyze the relevant performances, demonstrating enhanced efficiency and power tracking outputs. The proposed converter efficiency has improved to 94% with a minimal part count of 2 switched configurations. configuration. The applied control logic, in my opinion, Cascaded ANFIS is capable of operating the BLDC with an operational efficiency of 98.92%, including better output voltage generations of 350 V. [ABSTRACT FROM AUTHOR]

Hydrogen-based electric vehicles such as Fuel Cell Electric Vehicles (FCHEVs) play an important role in producing zero carbon emissions and in reducing the pressure from the fuel economy crisis, simultaneously. This paper aims to address the energy management design for various performance metrics, such as power tracking and system accuracy, fuel cell lifetime, battery lifetime, and reduction of transient and peak current on Polymer Electrolyte Membrane Fuel Cell (PEMFC) and Li-ion batteries. The proposed algorithm includes a combination of reinforcement learning algorithms in low-level control loops and high-level supervisory control based on fuzzy logic load sharing, which is implemented in the system under consideration. More specifically, this research paper establishes a power system model with three DC-DC converters, which includes a hierarchical energy management framework employed in a two-layer control strategy. Three loop control strategies for hybrid electric vehicles based on reinforcement learning are designed in the low-level layer control strategy. The Deep Deterministic Policy Gradient with Twin Delayed (DDPG TD3) is used with a network. Three DRL controllers are designed using the hierarchical energy optimization control architecture. The comparative results between the two strategies, Deep Reinforcement Learning and Fuzzy logic supervisory control (DRL-F) and Super-Twisting algorithm and Fuzzy logic supervisory control (STW-F) under the EUDC driving cycle indicate that the proposed model DRL-F can ensure the Root Mean Square Error (RMSE) reduction for 21.05% compared to the STW-F and the Mean Error reduction for 8.31% compared to the STW-F method. The results demonstrate a more robust, accurate and precise system alongside uncertainties and disturbances in the Energy Management System (EMS) of FCHEV based on an advanced learning method. [ABSTRACT FROM AUTHOR]

Essential for compact and lightweight proton exchange membrane fuel cell (PEMFC) stacks, metallic bipolar plates (MBPs) suffer from durability and conductivity issues due to surface corrosion and passivation. This study conducts ex-situ characterization of Cr 2 SiC ceramic MAX phase coatings on stainless steel (SS) 316 L substrates to evaluate their suitability for MBP application. The investigation encompasses coating structure, surface morphology, corrosion resistance, surface wettability, in-plane electrical conductivity, and interfacial contact resistance. X-ray diffraction and X-ray photoelectron spectroscopy confirm the presence of Cr 2 SiC coatings on SS316L, while energy-dispersive X-ray spectroscopy verifies uniform coverage and elemental weight percentage. Corrosion resistance is evaluated using potentiostatic and potentiodynamic polarization tests, showing excellent resistance with low corrosion current density (I corr) at both 25 °C (3.29E-03 μA/cm2) and 80 °C (4.32E-02 μA/cm2), meeting US Department of Energy (DOE) technical targets. Potentiodynamic polarization reveals large corrosion potential and small I corr values at both temperatures, outperforming uncoated samples. Electrochemical impedance spectroscopy post-accelerated corrosion tests show high charge transfer resistance at 25 °C (3.68E+05 Ω cm2) and 80 °C (3.02E+05 Ω cm2), indicating stability in acidic environments. Surface wettability analysis indicates low water affinity with a large contact angle (75°) and low surface free energy (28.92 mJ/m2) for the coated samples as compared to the uncoated samples. Electrical conductivity meets DOE targets with an in-plane conductivity of 4.59E+05 S/m and interfacial contact resistance of 8.04 mΩcm2 after 5-h accelerated corrosion tests at 80 °C. These results suggest that Cr 2 SiC coated SS316L exhibits excellent corrosion resistance, surface wettability, and electrical characteristics, making them viable for PEMFC applications. • Developed Cr 2 SiC coated samples demonstrate improved durability and conductivity. • Corrosion behaviour met Department of Energy (DOE) targets at 25 °C and 80 °C. • Coated samples maintained high charge transfer resistance post-accelerated corrosion. • Surface wettability analysis of coated samples revealed low water affinity. • Electrical characteristics of Cr 2 SiC coatings met DOE targets post-corrosion. [ABSTRACT FROM AUTHOR]

Investigating the chemical and mechanical degradation phenomena of polymer electrolyte membranes (PEMs) is crucial, as they significantly influence the electrochemical performance and lifetime of fuel cell electric vehicles. For this, the combined use of chemical and mechanical accelerated stress test (AST) protocols has proven effective and reliable in evaluating PEMs durability within a relatively short period. However, it remains unclear whether the combined AST protocols exclusively affect PEMs durability, since the AST evaluation is performed not in the membrane states but in the membrane-electrode assembly (MEA) state. To address this question, a combined AST protocol consisting of a single cycle involving a chemical degradation phase followed by a mechanical degradation phase, was applied. The influence of the combined AST on both the membrane and electrodes was investigated using a variety of electrochemical evaluations conducted after each cycle. Additionally, the study includes changes in the physical characteristics of each MEA component. This study deals with the degradation behavior of MEA obtained after a combined chemical/mechanical accelerated stress test to evaluate the membrane durability for polymer electrolyte fuel cells. [Display omitted] • Combined chemical/mechanical AST impact on PEMFC membrane and electrodes. • Electrochemical and physical characteristics are monitored as the AST progresses. • Chemical and mechanical degradation analyzed from membrane and electrode perspectives. [ABSTRACT FROM AUTHOR]

The cathode catalyst layer (CCL) provides the core site for the electrochemical reactions that occur in the proton exchange membrane fuel cell (PEMFC). Its composition directly determines the electrochemical and mass transfer performance of the fuel cell. Current experimental and modeling methodologies still have shortcomings in the comprehensive optimization of CCL performance. Therefore, this work proposes a machine learning framework combining a data-driven surrogate model and multi-objective optimization to effectively evaluate the influence of CCL compositions on three novel performance indexes, including voltage (V cell), average value of CCL oxygen concentration (C O 2 ), and water saturation (CCL sat). Firstly, CCL agglomerate model is integrated with the multi-physics PEMFC model to achieve an accurate characterization of performance. Numerical simulations provide a reliable database for training the surrogate model based on back propagation neural network (BPNN). Subsequently, the surrogate model is integrated with non-dominated sorting genetic algorithm-Ⅱ (NSGA-II) to expedite the assessment of fitness value for optimizing three performance indexes. Finally, the optimal CCL composition scheme located on the Pareto frontier is prioritized through the technique for order preference by similarity to an ideal solution (TOPSIS). The results show that the decision-optimal model demonstrates varying degrees of improvement compared to the base model, with a 6.17% improvement in V cell , increases of 5.84% in C O 2 , and reductions of 3.77% in CCL sat at 1 A cm−2. Therefore, a novel integrated optimization framework considering multi-factors and multi-objectives proposed in this study is of great significance in seeking the optimal CCL composition parameters and ultimately enhancing the comprehensive performance of PEMFC to accelerate its commercial application. • Voltage, oxygen concentration, and water saturation are proposed as performance indexes. • The comprehensive PEMFC model is validated by experimental data. • A novel integrated optimization framework for CCL is proposed. • Optimal model demonstrates remarkable improvement and credibility. • An appropriate trade-off between CCL electrochemical and mass transfer performance is revealed. [ABSTRACT FROM AUTHOR]