Search

Due to stringent environmental regulations and the limited resources of fossil-based fuels, there is an urgent demand for clean and eco-friendly energy conversion devices. These criteria appear to be met by hydrogen proton exchange membrane fuel cells (PEMFCs). PEMFCs have attracted tremendous attention on account of their excellent performance with tunable operability and good portability. Nonetheless, their practical applications are hugely influenced by the scarcity and high cost of platinum (Pt) used as electrocatalysts at both cathode and anode. Pt is also susceptible to easy catalyst poisoning. Herein, this paper reviews the progress of the research regarding the development of electrocatalysts practically used in hydrogen PEMFCs, where the corner-stone reactions are cathodic oxygen reduction reaction (ORR) and anodic hydrogen oxidation reaction (HOR). To reduce the costs of PEMFCs, lessening or eliminating the use of Pt is of prime importance. For current and forthcoming laboratory/large-scale PEMFCs, there is much interest in developing substitute catalysts based on cheaper materials. As such are non-platinum (non-Pt), non-platinum group metals (non-PGMs), metal oxides, and non-metal electrocatalysts. Hence, high-performance, state-of-the-art, and novel structured electrocatalysts as replacements for Pt are needed.

In a proton-exchange membrane water-electrolysis system, performance is greatly affected by the anode materials and operation modes. Moreover, high voltages allow greater hydrogen production as well as the potential of creating ozone for green disinfection. However, after switching off power and restarting, a big decrease in performance drop as well as hydrogen/ozone generation. In this study, different additives—multi-wall carbon nanotubes, surface-modification graphene, reduction graphene oxide, and graphene oxide—are adopted and mixed with PbO2 and to create anode catalyst ink. The characteristics of the anode catalysts are investigated with voltage-current test, interruptive power supply, electrochemical impedance spectroscopy and high voltage accelerating tests. The results show that the anode of MEA with additive, multi-wall carbon nanotubes or multi-wall carbon nanotubes plus surface-modification graphene, lead to twice higher performance. Further, anode of MEA with additive, multi-wall carbon nanotubes, multi-wall carbon nanotubes plus graphene oxide, and multi-wall carbon nanotubes plus reduction graphene oxide, displays better restoration (34–36%↓).

Bimetallic PtPd nanowires are produced by the centrifugal electrospinning method and their application as electrocatalysts in the cathode of a proton exchange membrane fuel cell (PEMFC) is evaluated. The effects of system parameters on the morphology of PtPd nanowires after calcination are explored including the rotation speed of spinneret, applied electric field, and atomic ratio of Pt and Pd in the composition. Cyclic voltammetry tests are conducted to characterize the electrochemical property and the produced PtPd nanowires are employed to fabricate the cathode catalyst layer in a PEMFC. The cell performance is measured and compared with commercial Pt/C electrocatalysts. Results show that bimetallic PtPd nanowires can be produced successfully with minimum mean diameter of 79 ± 24 nm and maximum electrochemical active surface area (ECSA) of 10.29 m 2 g − 1 at the atomic ratio Pt:Pd = 3:1. By the accelerated degradation tests, the PtPd nanowires demonstrate better durability than Pt/C. The present results reveal that the centrifugal electrospinning method can successfully fabricate PtPd nanowires which have great potential to be utilized in PEMFCs.

This study analyzes the characteristic numerical analysis of membrane electrode assembly in Proton Exchange Membrane Fuel Cell (PEMFC) with bipolar plate, flow channel, gas diffusion electrode, and proton exchange membrane. The numerical solution focuses on discussing the effects of different parameters, including permeability, porosity, and operation voltage, on various mass fractions, current-voltage curve, and power-voltage curve. The results show that as the porous medium with high gas permeability is an important factor that affects the mass fraction of hydrogen. Regarding the analyses of various porosities, the fuel cell performance can be effectively promoted with larger ratio of porosity and permeability. However, increasing the porosity will affect the electrical conductivity and increase the flooding of water, which will block the flow channel and reduce efficiency.

Hydrogen is rapidly turning into one of the essential energy carriers for future sustainable energy systems. The main reason for this is the possibility of off-peak excess power production and storage of renewable stations such as wind farms, photovoltaic plants, etc. For hydrogen (itself) or its sub-productions methanol, ammonia, etc. Such energy systems are so-called power2X technologies. For hydrogen and other biogases, using a fuel cell is a promising method for returning the fuel to the power grid or electric cars in the form of electricity. In this paper, a novel hybrid energy system consisting of a molten carbonate fuel cell (MCFC) and different options to generate hydrogen from the waste heat of the MCFC is investigated. The system consists of two scenarios of weather using proton exchange membrane electrolyzer (PEME) of vanadium chloride (VCL) cycle. The article presents a comprehensive thermodynamic, economic, and environmental analysis of the system optimized by tri-objective optimization (as an innovative optimization) methods. The aim of the optimization task here is to minimize the costs and emissions while maximizing efficiency. A parametric study is conducted to see the effect of different design parameters on the system's performance. Results demonstrate that fuel utilization factor, stack temperature, and current density have the most critical effect on the system performance. In addition, the system coupled with the VCL cycle exhibits better performance than the system with PEME. In addition, at the optimized point, the efficiency, cost rate, and emission become 69.28%, 3.73 ($/GJ), and 1.16 kg/kWh, respectively. In addition, the produced hydrogen in VCL and PEME are 585 kg/day and 293 kg/day respectively.

This article is a careful examination of an energy poly-generation unit integrated with an evacuated solar thermal tube collector. A proton exchange membrane (PEM) electrolysis unit is used for hydrogen production, an ejector refrigeration system (ERS) is utilized for cooling demand, and a heater unit is used for heating demand. All sub-systems are validated by considering recent articles. Cooling and heating demand, as well as the net output power are calculated. The modeled poly-generation system's exergy and energy efficiency are maximized by considering the inlet temperature of the heat exchanger and primary pressure of the ejector with the parametric evaluation of the system. The proposed poly-generation set-up can produce cooling load, heating load, and hydrogen with amounts of 5.34 kW, 5.152 kW, and 63 kg/year, respectively. Based on these values, the energy efficiency, and exergy efficiency are computed to be 64.14%, and 49.62%, respectively. Higher energy and exergy efficiencies are obtained by reducing high pressure of the refrigeration cycle or decreasing the temperature outlet of an auxiliary heater. The heat exchanger and thermal energy storage unit have the highest cost rate among all system components with 73,463 $ and 46,357, respectively. Parametric study indicates that the main determinative elements in the total cost rate of the system are the heater, and the solar collector.

In the current work, thermodynamic examination for cogeneration of electricity and cooling based on a polymer exchange membrane (PEM) fuel cell was carried out. To the waste energy in the fuel cell, an absorption refrigeration unit is employed in two modes with ejector and without ejector. This system includes a PEM-FC, an absorption refrigeration unit, a hydrogen storage tank, an ejector, and an air compressor. The produced thermal energy in the fuel cell is received entirely by a working fluid and is given to the absorption chiller generator. The system simulation was carried out from two perspectives of energy and fuel saving. Findings showed that the energy efficiency of the combined cooling and power (CCP) unit and the CCP system equipped with the ejector (CCP-E) was 63.72% and 78.33%, respectively. It indicated that adding the ejector to the system increases the energy efficiency of the system by 23%. The fuel economy percentages of the CCP system and CCP-E were 44.43% and 45.9%, respectively. The results also showed that adding the ejector in the refrigeration system increases the system performance by up to 44%. The presence of the ejector causes the working fluid flow in the evaporator to increase with the suction of the secondary flow, and the cooling capacity increases significantly. Moreover, with increasing generator and evaporator pressure, the suction ratio of the cooling system equipped with the ejector decreases and increases, respectively.

Because of the current increase in energy requirement, reduction in fossil fuels, and global warming, as well as pollution, a suitable and promising alternative to the non-renewable energy sources is proton exchange membrane fuel cells. Hence, the efficiency of the renewable energy source can be increased by extracting the precise values for each of the parameters of the renewable mathematical model. Various optimization algorithms have been proposed and developed in order to estimate the parameters of proton exchange membrane fuel cells. In this manuscript, a novel hybrid algorithm, i.e., Hybrid Particle Swarm Optimization Puffer Fish (HPSOPF), based on the Particle Swarm Optimization and Puffer Fish algorithms, was proposed to estimate the proton exchange membrane fuel cell parameters. The two models were taken for the parameter estimation of proton exchange membrane fuel cells, i.e., Ballard Mark V and Avista SR-12 model. Firstly, justification of the proposed algorithm was achieved by benchmarking it on 10 functions and then a comparison of the parameter estimation results obtained using the Hybrid Particle Swarm Optimization Puffer Fish algorithm was done with other meta-heuristic algorithms, i.e., Particle Swarm Optimization, Puffer Fish algorithm, Grey Wolf Optimization, Grey Wolf Optimization Cuckoo Search, and Particle Swarm Optimization Grey Wolf Optimization. The sum of the square error was used as an evaluation metric for the performance evaluation and efficiency of the proposed algorithm. The results obtained show that the value of the sum of square error was smallest in the case of the proposed HPSOPF, while for the Ballard Mark V model it was 6.621 × 10−9 and for the Avista SR-12 model it was 5.65 × 10−8. To check the superiority and robustness of the proposed algorithm computation time, voltage–current (V–I) curve, power–current (P–I) curve, convergence curve, different operating temperature conditions, and different pressure results were obtained. From these results, it is concluded that the Hybrid Particle Swarm Optimization Puffer Fish algorithm had a better performance in comparison with the other compared algorithms. Furthermore, a non-parametric test, i.e., the Friedman Ranking Test, was performed and the results demonstrate that the efficiency and robustness of the proposed hybrid algorithm was superior.

Metal-organic frameworks (MOFs) are considered emerging materials as they further improve the various properties of polymer membranes used in energy applications, ranging from electrochemical storage and purification of hydrogen to proton exchange membrane fuel cells. Herein, we fabricate composite membranes consisting of polybenzimidazole (PBI) polymer as a matrix and MOFs as filler. Synthesis of ZIF-8 and UiO-66 MOFs are conducted through a typical solvothermal method, and composite membranes are fabricated with different MOF compositions (e.g., 2.5, 5.0, 7.5, and 10.0 wt %). We report a significant improvement in proton conductivity compared with the pristine PBI; for example, more than a three-fold increase in conductivity is observed when the PBI-UiO66 (10.0 wt %) and PBI-ZIF8 (10.0 wt %) membranes are tested at 160 °C. Proton conductivities of the composite membranes vary between 0.225 and 0.316 S cm−1 at 140 and 160 °C. For the comparison, pure PBI exhibits 0.060 S cm−1 at 140 °C and 0.083 S cm−1 at 160 °C. However, we also report a decrease in permeability and mechanical stability with the composite membranes.

Refereed/Peer-reviewed This study demonstrates the successful development of hybrid mesoporous siliceous phosphotungstic acid (mPTA-Si) and sulfonated poly ether ether ketone (SPEEK) as a proton exchange membrane with a high performance in hydrogen proton exchange membrane fuel cells (PEMFC). SPEEK acts as a polymeric membrane matrix and mPTA-Si acts as the mechanical reinforcer and proton conducting enhancer. Interestingly, incorporating mPTA-Si did not affect the morphological aspect of SPEEK as dense membrane upon loading the amount of mPTA-Si up to 2.5 wt%. The water uptake reduced to 14% from 21.5% when mPTA-Si content increases from 0.5 to 2.5 wt% respectively. Meanwhile, the proton conductivity increased to 0.01 Scm−1 with 1.0 wt% mPTA-Si and maximum power density of 180.87 mWcm−2 which is 200% improvement as compared to pristine SPEEK membrane. The systematic study of hybrid SP-mPTA-Si membrane proved a substantial enhancement in the performance together with further improvement on physicochemical properties of parent SPEEK membrane desirable for the PEMFC application.

Although many studies have been done on finding operating conditions of hydrogen-fed fuel cells before, it remains one of the most critical points in determining its parameters in the process. So this paper aims to investigate experimentally the reactant gases flow rate and cell voltage which have a significant impact on the current density of a 3-cell Proton Exchange Membrane fuel cell stack having a 150 cm2 active layer. In this case, to determine the optimum values, Design of Experiment and Response Surface Methodology was applied to the experimental system at low 1.5 V, medium 1.8 V, and high 2.1 V. Then, they were compared with each other. In this context, keeping the hydrogen flow rate low and obtaining high current density is one of the main targets; at low voltage values, it was concluded that the flow rate should be increased due to the reaction rate increases with temperature. In general, the effect of humidification and cell temperature on performance was seen more prominently at 1.8 V. The highest current density values that were 313.66 mA/cm2, 336.75 mA/cm2, and 323.48 mA/cm2, respectively, were reached at flow rates of 1 L/min,1.3 L/min,1.6 L/min.

International audience; Proton exchange membrane fuel cell (PEMFC) long-term prognostic facilitates reducing the time/cost of the durability tests and is a critical starting point for control/maintenance suggestions. Long short-term memory (LSTM) recurrent neural networks have excellent time series processing capabilities and are proved to be useful for the short-term prognostic of PEMFC. However, LSTM prognostic models usually suffer from accumulated errors and model recognition uncertainties, which make it difficult to break the historical degradation data limitations, resulting in unsatisfactory long-term prediction performance. To tackle the problem, this paper proposes a novel model named navigation sequence driven LSTM (NSD-LSTM) for long-term prognostic. In the strategy, a navigation sequence is firstly generated by using an autoregressive integrated moving average model with exogenous variables. The sequence is then fed iteratively into LSTM in the implementation stage to achieve long-term perdition. The proposed strategy is evaluated using the aging experimental data of two types of PEMFC under different operating conditions. The long-term prognostic performance of the proposed model and other two state-of-the-art prognostic models, namely, nonlinear autoregressive exogenous and echo state network, are evaluated through comparison experiments. The simulation and experimental results show that the proposed prognostic strategy has better long-term degradation trend prediction consistency and remaining useful life estimation robustness.

Here, an optimal linear parameter varying (LPV) controller is developed for non‐linear proton exchange membrane fuel cell (PEMFC) systems. Two performance criteria are involved in the optimal controller, including the membrane pressure and the power of the PEMFC. The former should be minimized; and, the latter should be maximized. Since the goal is to derive sufficient conditions in terms of linear matrix inequality (LMI) constraints, both performances are re‐formulated and augmented in a unique convex optimization problem. Further, the non‐linear PEMFC with the equilibrium profile dependent on time‐varying parameters, that is, current and temperature, is represented by an LPV model. Using the LMI constraints and the obtained LPV model, the gains of the controller are derived. Comparing with the state‐of‐the‐art methods, the proposed approach offers an optimal control approach with a systematic design method, in which both practical issues are treated, simultaneously. To show the advantages of the developed approach, six typical controllers, including the proposed and existing approaches, are considered and several numerical simulation results are conducted.

The hybrid sulfur (HyS) process, which is composed of SO2-depolarized electrolysis (SDE) reaction and sulfuric decomposition reaction, is one of the simplest thermochemical cycles for producing hydrogen by water splitting. SDE is currently conducted in a proton exchange membrane (PEM) electrolyzer. In this work, a novel PEM electrolyzer structure is proposed. Graphite felt with large void content is used as the diffusion layer. In the electrolyzer, porous graphite felt plays the role of evenly distributing fluid and conducting electricity. The gap between the polar plate and the catalytic layer is occupied by the electrolyte solution and graphite felt, which effectively reduces the ohmic impedance of the electrolyzer. The effects of the main parameters including graphite felt compression ratio, anodic fluid flow rate, and sulfuric acid concentration, as well as temperature are investigated. Under optimized operating conditions, the current density reaches 800 mA/cm2 at cell voltage of 1.094 V, which is remarkably better than reported SDE performance using conventional PEM electrolyzers.

This work addresses the issues of long-term leakage rate prediction, which is crucial for durability study of proton exchange membrane fuel cells (PEMFCs). A theoretical model is presented for the leakage rate of compressive seal structures in PEMFCs, based on the combination of three numerical techniques, namely Lattice-Boltzmann method (LBM) simulations for rough wall interfacial gaps, a numerical 3D rough-surface generation technique, and Finite-Element-Analysis (FEA) for micro-contact mechanics of single asperity. The model clearly reveals the quantitative influence of various factors on the leakage rate without any empirical regression coefficients, and therefore can be easily integrated with structural mechanics and aging mechanism analyses. Long term sealing performance comparisons with three types of rubber material identify liquid silicone rubber to have the optimal durability. When influences of water environment are taken into account, an accelerated degradation of sealing performance can be observed after approximately 3000 h of operation. In addition, the effect of stress loss on leakage rate can be effectively suppressed by reducing surface roughness, reducing gasket thickness and increasing strain level. The proposed theoretical model provides an effective approach for the design of metal-bipolar-plate PEMFCs seal structures.

Mechanical durability of hydrocarbon-based proton exchange membranes in long-term fuel cell operation is vital for their successful commercialization. Herein, a complex finite element model is developed that couples electrochemical performance of sulfonated poly(ether ether ketone) (SPEEK) membrane with its mechanical response at different operating conditions to predict the susceptible sites to mechanical failure. To this end, the impacts of cell voltage (0.1–0.9 V), operating temperature (30–80 °C) and backpressure (0.3–1.5 bar), inlet reactants relative humidity (30–100%), and clamping pressure (1–5 MPa) on hydration and consequently, stress and strain formation in the SPEEK membrane are investigated. Results suggest that SPEEK membrane, particularly at the channel outlet, undergoes the greatest swelling-induced degradation when the cell is running at low voltages, high temperature and backpressure values. Clamping pressure, however, imposes compressive stress and thinning upon the land region and is the dominant factor compared to hygrothermal swelling, albeit high hydration level shifts the maximum stress to the channel region. Despite superior resistance to different hygrothermal conditions and lower chance of thinning under the clamping pressure, Nafion membrane exhibits a relatively higher risk of wrinkle deformation under compression. This study provides insights into the mechanical response of hydrocarbon-based membranes under various fuel cell conditions.

Nafion, a perfluoro-sulfonic acid (PFSA)-based polymer, is a promising material that will help realize the commercialization of proton exchange membrane-based fuel cells (PEMFCs) and proton exchange membrane water electrolyzers (PEMWEs). However, Nafion also exhibits reduced mechanical and dimensional stability and increased hydrogen crossover under cell operating conditions in real operational settings, that is, in a hydrated state or in water at 60–80 °C. These factors may negatively affect cell efficiency and durability and thus must be addressed. To overcome these limitations, polyamide-coated Nafion composite membranes were developed for the first time via interfacial polymerization. 3,5-Diaminobenzoic acid (DABA), which contains carboxyl functional groups, was used as a monomer to add hydrophilicity to the membrane, and the coating layer thickness was controlled by adjusting the DABA content. A nanoscale polyamide (PA) layer was coated on the surface of Nafion-212 to fabricate a membrane, PA-c3-Nafion. PA-c3-Nafion was found to show ion conductivity 13.6% higher than that of a pristine Nafion-212 membrane at 80 °C, while providing improved mechanical performance and dimensional stability. In particular, at 95% RH, the hydrogen permeability of PA-c3-Nafion was 16.4% lower than that of Nafion-212 while, in a fully hydrated state, the hydrogen permeability of PA-c3-Nafion was 21.2% lower than that of Nafion-212. The LSV test results also showed that the degree of hydrogen crossover was significantly lower in PA-c3-Nafion than in Nafion-212.

High-loaded oxygen reduction reaction (ORR) Pt intermetallic compounds with high performance expression under PEMFC operating conditions are prerequisite for practical application. Nevertheless, high metal-loading would lead to the severe agglomeration and nonuniformity of nanoparticles, imposing an enormous challenge on efficient synthesis. Herein we present a cobalt oxide aided structural evolution strategy to controllably synthesize high-loaded (44.7 wt%) sub-6 nm Pt1Co1 intermetallic compound with Pt-rich shell (Pt1Co1-IMC@Pt). Experiments and theory explicitly reveal that the ordered arrangement of Pt-Co atoms endows surface Pt with lowered d band centre and enhanced oxidation-resistance of Pt/Co sites, thus simultaneously boosting the ORR activity and durability. The preeminent intrinsic ORR activity on an optimized catalyst reaches a mass activity as high as 0.53 A mg(Pt)-1 @0.90V/RHE (MA@0.9 V) in rotating disk electrode measurement. PEMFCs with such a catalyst deliver the record-high power density (2.30/1.23 Wcm-2 under H2-air/O2 conditions at 80 oC) and extraordinary stability, ranking the highest fuel cell performance among the Pt-based electrocatalysts. Significantly, the MA@0.9 V calculated from fuel cell attains 0.46 A mg(Pt)-1, exceeding the 2020 DOE target (0.44 A mg(Pt)-1) and very close to the intrinsic value, definitely confirming the superiority of high-loaded Pt1Co1-IMC@Pt/C in activity expression under fuel cell conditions. This study paves a new way for the future practical application of low-Pt catalysts in PEMFCs.

To systematically explore the low-temperature operating characteristics of polymer electrolyte membrane fuel cell (PEMFC) stack, a three-dimensional PEMFC stack model with intake manifold is developed in this study. The characteristics of different cold start modes in the stack are compared and analyzed. The distribution and transmission characteristics of water, ice, and heat in each cell of the stack are analyzed in detail. The location of water accumulation in each cell of the stack is also explored. Finally, finite difference sensitivity is calculated for the cumulated charge transfer density to quantify the effects of operating parameters on the cold start process at low temperature. And how these parameters affect the operation of the PEMFC stack at low temperature is investigated. The results show that inconsistency exists in stack operation due to the position particularity of the intermediate cell. Irreversible heat is the main heat source for the cold start of the stack, and the cathode catalyst layer is the main heat-generating component. The heat production proportion of cathode catalyst layer can reach 90%, which decreases with the increment of current density and the running time, especially for the edge cell. The initial ionomer water content is most sensitive to the cold start process of the stack, followed by the porosity of cathode catalyst layer. These parameters are sensitive to the cold start process mainly because of the change in volumetric exchange current density and oxygen concentration.

The proton exchange membrane fuel cell (PEMFC) stack is a key component in the fuel cell/battery hybrid vehicle. Thermal management and optimized control of the PEMFC under real driving cycle remains a challenging issue. This paper presents a new hybrid vehicle model, including simulations of diver behavior, vehicle dynamic, vehicle control unit, energy control unit, PEMFC stack, cooling system, battery, DC/DC converter, and motor. The stack model had been validated against experimental results. The aim is to model and analyze the characteristics of the 30 kW PEMFC stack regulated by its cooling system under actual driving conditions. Under actual driving cycles (0–65 kW/h), 33%–50% of the total energy becomes stack heat; the heat dissipation requirements of the PEMFC stack are high and increase at high speed and acceleration. A PID control is proposed; the cooling water flow rate is adjusted; the control succeeded in stabilizing the stack temperature at 350 K at actual driving conditions. Constant and relative lower inlet cooling water temperature (340 K) improves the regulation ability of the PID control. The hybrid vehicle model can provide a theoretical basis for the thermal management of the PEMFC stack in complex vehicle driving conditions.

The storage problem at low temperatures is one of the technical barriers to commercialization in the future for the polymer electrolyte membrane fuel cell (PEMFC). In this study, the resistance relaxation characteristic under different pretreatment methods before low-temperature storage of PEMFC is analyzed. The effect of residual water in different PEMFC locations on its storage performance after thermal cycles are investigated. The evolution curves of resistance after the purging process are different under equilibrium, cold, and hot purge and the percentage drop of cell resistance at relaxation stage under three methods are 14.5%, 66.3%, and 73.1%. It is found that the most likely reason for relaxation is membrane water structure reorganization. The voltage of the cell with no purge and purged to the end of the first stage becomes smaller at low current density after 20 freeze/thaw cycles. The charge transfer resistances of the cell with no purge, purged to the end of the first stage, and purged to the end of the second stage increase by 8.2%, 15.6%, and 7.4%, respectively. And the cell purged to the end of the first stage has the largest decay rate of electrochemical surface area. The result implies that the performance degradation after freeze/thaw cycles is associated with the water in the ionomer of catalyst layers, which freezes between ionomers and Pt particles at low temperatures.

In this study, experimental methods are used to study the effect of assembly torque and channel size on cold start performance. Through the analysis of pressure distribution, fuel cell voltage, cathode gas inlet and outlet pressure drop and high frequency impedance, it is considered that, under the experimental conditions of this study, the fuel cell assembly torque is 2 N m, which has better cold start performance than the assembly torque of 1 N m and 4 N m. In addition, Under the condition of 2 N m assembly torque, the effect of four different flow channel sizes on the pressure distribution and cold start performance of the fuel cell was studied. It is found that when the width of channel is 0.5 mm, the depth of channel is 0.3 mm, the cold start performance is best.

Enhancing mass transfer capability of flow channel is important subject to improve fuel cell performance. In this study, an experimental study about non-uniform arrangement of metallic structures in cathodic flow channel on polymer electrolyte membrane fuel cell is conducted. Metallic 3D printer is used to manufacture 3D mesh with complex geometry. Channel width and bottom-rear channel depth are selected to change the geometry of structure. Assuming that accelerating flow velocity and reinforcing flow direction to gas diffusion layer can improve fuel cell performance, eight basic arrangements are inserted into cathodic carbon bipolar plate to measure fuel cell performance. With I–V curve, the unit cells with non-uniform arrangements of width and tapered structure show performance enhancement of 12.8% in maximum power density, compared with conventional parallel flow channel. According to electrochemical impedance spectroscopy results, performance enhancement by non-uniform arrangement is mainly occur in high current density operation due to low mass transfer resistance.

Radiation-induced graft polymerization is introduced to effectively fabricate proton exchange membrane based on 12.5 μm fluorinated ethylene propylene (FEP) film. The graft side chains penetrate FEP film and distribute inside the bulk matrix evenly. The membranes exhibit hydrophilic/hydrophobic microphase-separated morphology as well as good thermal stability. The influences of irradiation parameters on the membrane property are investigated and the resulting membranes (named FEP-g-PSSA) exhibit excellent physicochemical properties. Membrane with 27.48% degree of graft and 130.1 mS cm−1 proton conductivity is employed for fuel cell performance measurement. Under optimized operate conditions (80 °C, 75% relative humidity), the power density could reach up to 0.896 W cm−2, inspiring for fuel cell application. The mass-transport-controlled polarization of membrane electrode assembly (MEA) based on FEP-g-PSSA membrane is higher than Nafion® 211 within the whole current density range and the gap is widening with increasing current density. At 2.0 A cm−2, the mass transfer polarization of FEP-g-PSSA reaches up to 0.204 V, far higher than Nafion® 211 (0.084 V). By promoting the compatibility between the ionomer in the catalyst layer and FEP-g-PSSA membrane and optimizing the membrane/catalyst layer/gas diffusion layer interfaces, the fuel cell performance could be significantly enhanced, making the FEP-g-PSSA membranes promising in fuel cell application.

A hybrid system with jointed battery and PEMFC is popular and of great potential in New Energy Vehicle (NEV) application. However, reliability and efficiency remain to be improved for commercial products. To reflect the complicated physics inside the proton exchange membrane fuel cell (PEMFC), the PEMFC model consisting of inner muti-physics process and other accessories was built, then a complete hybrid system was established when a matched battery, DC/DC, regenerative braking were taken into consideration. Based on the above model, the stack state and system performance under standard cycle for heavy duty vehicle-CWTVC were obtained. According to the simulation results, fuel cell states such as pressure, water content and voltage suffers severe oscillation with external load, especially in the highway cycle. Membrane electrode assembly (MEA) suffers from pressure impact with average value of more than 24 kPa in highway cycle. In the aspect of relative humidity, the PEMFC stack is most threatened in road cycle. As for the hybrid system, its efficiency and state of charge (SOC) fluctuation perform worst in urban cycle and road cycle respectively, while its highest efficiency occurs in road test. Operating mode of fuel cell has influence on hybrid system. When 3-level mode of fuel cell output was applied, the efficiency increased to its peak value at medium level of 28 kW and then declined gradually. H2 consumption had an opposite trend compared to efficiency. In the aspect of battery SOC, it declines in operating process and its fluctuations decreases when medium level got bigger. The 3-level mode and 4-level mode were compared using this model. It can be concluded that although 3-level mode performs slightly better in hybrid system efficiency, H2 consumption, pressure impact, it does not have absolute advantage over 4-level mode in other indicators.

Recently, researchers have devoted more attention to supercapacitors (SCs) to integrate with batteries in energy storage systems (ESSs) for vehicle applications. In this study, we attempted to characterize the use of SCs in the ESS for a PEM fuel cell vehicle equipped with an alternator to maximize the performance of regenerative braking. We applied lithium-ion batteries (LIBs) and SCs as energy storage devices to examine their effect on ESS. Then we used a hysteresis brake to apply controllable braking force on the flywheel to form hybrid braking (HB) and made efforts to study its behavior to suggest a braking control strategy. We also ran the whole system over the rotational speed to cover the range of driving speed. At last, we sized the SCs for the most commonly used fuel cell electric vehicle (FCEV) in Korea, i.e., Hyundai NEXO, based on the results obtained from the above study by alternator efficiencies.

A common problem associated with FeNC catalysts is their poor stability dominated by the carbon oxidation reaction (COR). In this work, the feasibility of stabilizing FeNC catalysts with small quantities of Ir was explored. With iridium being present, instead of COR the oxygen evolution reaction should be favored. The impact on structure and morphology was investigated by 57Fe Mössbauer spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. The catalytic activity and durability for the oxygen reduction reaction was evaluated by rotating ring disc electrode experiments and accelerated stress tests mimicking the start-up and shutdown cycle (SSC) conditions, respectively. For selected samples the stability was analysed for SSCs in proton exchange membrane fuel cells. Moreover, the faradaic efficiency towards oxygen evolution reaction vs. COR was determined and the resistance towards COR analysed by in situ Raman spectroscopy. The results indicate indeed a suppression of the COR; however, specifically for fuel cell applications, further optimization is necessary.

Cost-effective and highly efficient Fe–N–C single-atom catalysts (SACs) have been considered to be one of the most promising potential Pt substitutes for the cathodic oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). Nevertheless, they are subject to severe oxidative corrosion originating from the Fenton reaction, leading to poor long-time durability of PEMFCs. Herein, we propose a MnOx engineered Fe–N–C SAC (Mn–Fe–N–C SAC) to reduce and even eliminate the stability issue, as MnOx accelerates the degradation of the H2O2 by-product via a disproportionation reaction to weaken the Fenton reaction. As a result, the Mn–Fe–N–C SAC shows an ultralow H2O2 yield and a negligible half-wave potential shift after 10 000 continuous potential cycles, demonstrating excellent ORR stability. Besides, the Mn–Fe–N–C SAC also shows an improved ORR activity compared to the common Fe–N–C SAC. Results show that the MnOx interacts with the Fe–Nx site, possibly forming Fe–Mn or Fe–O–Mn bonds, and enhances the intrinsic activity of single iron sites. This work provides a method to overcome the stability problem of Fe–N–C SACs while still yielding excellent catalytic activity, thus showing great promise for application in PEMFCs.

In this work, coupling effects of water content, temperature, oxygen density, and polytetrafluoroethylene (PTFE) loading on oxygen transport through an ionomer thin film on a platinum surface in a catalyst layer of a proton exchange membrane (PEM) fuel cell are investigated using molecular dynamics approach. Taguchi orthogonal algorithm is employed to comprehensively analyze the coupling effects in a limited number of cases. It is found that the effect of operation temperature is the weakest among the four factors, which has the smallest effect index 14.4. Coupling effects including the PTFE loadings on the oxygen transfer through the ionomer thin film is uncovered. Less PTFE loadings should be beneficial for the oxygen transfer. The chemical potential gradient is considered as the major driven force for the oxygen transport through the ionomer thin film, and oxygen density is the dominating factor, significantly affecting the chemical potential in the thin film.

The hydrogen recirculation in proton exchange membrane fuel cell (PEMFC) is recommended for the hydrogen supply of PEMFC, and hydrogen ejectors are gradually being used in fuel cell vehicles due to low noise and low energy consumption. However, there is a lack of discussion about the influence of recirculation rate on the stack. Due to passive regulating mechanism of the ejectors, a miniature speed-adjustable peristaltic pump is used to simulate the hydrogen ejector in this study to investigate the effect of hydrogen recirculation on the performance of PEMFC stack. Experiments are conducted under different pump flow rates. The stack with hydrogen recirculation is proven to have better performance, but over high pump flow rate can lead to hydrogen shortage. It is interesting to find that the flow rate fluctuation of hydrogen inlet affects the stability of stack performance, and pressure drop and recovery time during purge process are proposed as effective indicators for performance analysis. Finally, pump flow rates between 60 ml/min and 105 ml/min are defined as “effective area”. Based on the analysis of effective indicators, keeping at “effective area” is further proved to improve the performance of the stack, which is also useful to design hydrogen recirculation.

Flow channel design has attracted more and more attention with the evolution of fuel cell technology. Compared with conventional 2D flow channel, 3D flow channel has been proved to improve the performance of proton exchange membrane fuel cell with great enhancement of reactant transport in many researches. In this paper, flow fields of parallel 2D, simplified 3D and 3D with inclination are presented to study the transport and distribution characteristics of reactant and water inside a fuel cell, and efficiency evaluation criterion is proposed to evaluate the superiority of the flow channel design. It is found that 3D flow fields are superior compared with parallel 2D flow channel, with improved capacity of mass transfer, uniform water distribution and advanced water removal ability. The performance improvements of both 3D flow channel designs become significant at elevated current density, with the output voltage increasing to 4.4% at 1.6 A cm−2 and up to 10% at 2 A cm−2. Compared with 3D flow channel with inclination, simplified 3D flow channel shows smaller pressure drop, and it has better performance than that of 2D flow channel. Considering both the performance and flow resistance, simplified 3D flow channel performs the best with high efficiency and easy-processing, thus it is the future direction of flow design.

In this article, thermodynamic modeling of a cogeneration system consisting of a series two-stage organic Rankine cycle (STORC) and a proton exchange membrane (PEM) fuel cell is conducted. The fuel cell dissipated heat is utilized as STORC plant input. In order to gain a higher efficiency for the proposed cogeneration system, the condenser of the organic Rankin cycle is replaced by a thermoelectric generator (TEG) to minimize heat loss. Moreover, zeotropic mixtures have been employed due to their lower irreversibility compared to single working fluid. Simulation code is developed in MATLAB software linked with the REFPROP software to extract the thermodynamic properties. This simulation code calculates the exergy efficiency and system's total cost rate. Since the performance of the system is affected by the working fluid, three zeotropic mixtures are compared with R123. The parametric study shows that high pressure (HP) and low pressure (LP) evaporator temperature, current density, and PEM operating pressure significantly affect the total cost rate and the second law efficiency. The results indicate that Ipentane-cis Butane has better efficiency among the selected zeotropic mixtures. Furthermore, the genetic algorithm multi-objective optimization is applied to determine the optimal design parameters of the system in a scatter distribution schematic. Finally, the normalized Pareto frontier of Ipentane-cis Butane is given and the related best point of working as a higher exergy efficiency and lower cost rate are specified. Eventually, it is concluded that the integration of STORC with primary PEM fuel cell improves overall exergy efficiency by 1.9%. The total cost rate for optimum point can be in a range of 1.36–14.94 ($/h), depending on the hydrogen production process.

To improve the drag reduction performances of the proton exchange membrane fuel cell (PEMFC), a three dimensional numerical investigation about the water removal in a lotus-like PEMFC flow channel is carried out. The effects of the microstructure shape parameters (height, radius and spacing) are investigated. The investigation revealed that the liquid water can be effectively removed by the lotus-like flow channel from the channel wall surface. The appropriate height of lotus-like channel can effectively reduce the water coverage ratio on the top wall of the lotus-like flow channel. As height increases, the average drag reduction ratio increases firstly and decreases finally. When the radiuses are 25 μm and 50 μm, the average drag reduction ratios of these cases are higher than those of the other cases obviously. The spacing of the lotus-like channel has a few effects on the water removal and water coverage ratio. The lotus-like flow channel with the height of 50 μm, the radius of 50 μm and the spacing of 150 μm has a high drag reduction and anti-corrosion performance. The work in this study provides a new choice for the flow channel and has certain guiding significance for the design of the flow channel for anti-corrosion and drag reduction.

This study presents a detailed review on the ultrathin catalyst layer (UTCL) design strategy for high-performance proton exchange membrane fuel cell (PEMFC). Specifically, the motivation towards the further reduced Pt loadings by applying the UTCL electrode design is firstly introduced from both the historical and mechanism deductions. Then, the recent developments on the UTCL designs belonging to different classifications are summarized with their respective merits. In particular, the critical issues remained on these ultra-thin, low Pt-loaded electrodes are proposed with alternative solutions. Finally, the whole review is concluded with the perspectives on the possible future directions settling the remaining challenges.

During the shutdown process of the fuel cell system for vehicles, the air entering the anode chamber can form the hydrogen/air interface, accelerating the carbon corrosion of the catalytic layer. According to optimized control strategies, the carbon corrosion of fuel cells can be reduced. Nowadays, the main control strategies include gas purging and the consumption of residual oxygen in the stack by the auxiliary load. However, the oxygen in the fuel cell stack cannot be fully consumed or can cause the single-cell voltage to rise to 0.8 V with an inappropriate discharge current drop rate and auxiliary load resistance value, thus affecting the protective effect of the shutdown strategy. In this work, a shutdown strategy of the fuel cell system is studied. After the experiment, the optimized value of the discharge current drop rate and the auxiliary load resistance were obtained. With the resistance value of 50 Ω and the current drop rate of 7 A/s, the shutdown time of the fuel cell system is 13.5 s and the time of single-cell voltage above 0.82 V in the fuel cell stack is 0.1 s. Thus, the optimized shutdown strategy can reduce the shutdown time.

Metal-nitrogen-carbons (M-N-Cs) as a reliable substitution for platinum-group-metals (PGMs) for oxygen reduction reaction (ORR) are emerging candidates to rationalize the technology of fuel cells. The development of M-N-Cs can further be economized by consuming waste biomass as an inexpensive carbon source for the electrocatalyst support. Herein, we report the simple fabrication and in-depth characterization of electrocatalysts using lignin-derived activated char. The activated char (LAC) was functionalized with metal phthalocyanine (FePc and MnPc) via atmosphere-controlled pyrolysis to produce monometallic M-N-Cs (L_Mn and L_Fe) and bimetallic M1-M2-N-Cs (L_FeMn) electrocatalysts. Raman spectroscopy and transmission electron microscopy (TEM) revealed a defect-rich architecture. XPS confirmed the coexistence of various nitrogen-containing active moieties. L_Fe and L_FeMn demonstrated appreciable ORR in both acidic and alkaline conditions whereas L_FeMn helped in restricting the peroxide yield, particularly in alkaline media. L_Fe and L_FeMn demonstrated remarkable onset potential (Eonset) of ∼0.942 V (vs RHE) with an E1/2 of 0.874 V (vs RHE) in 0.1 M KOH. In acid, L_FeMn had an Eonset of 0.817 V (vs RHE) and an E1/2 of ∼0.76 V (vs RHE). Finally, the L_FeMn as a cathode electrocatalyst was integrated and tested in PEMFC and AEMFC. AEMFC demonstrated optimistic performance with a peak power density of 261 mW cm−2 at the current density of ∼577 mA cm−2.

To comprehensively understand the CO poisoning effect on high-temperature PEMFC stack (HT-PEMFCs), a 3-D numerical HT-PEMFCs model is developed. The crucial anodic kinetic parameters are obtained from experimental data to improve the accuracy of the model. Then, multi-perspective analysis is conducted on different HT-PEMFC stacks with 1, 3, and 5 cells working at 160 °C with 3 mol% CO in H2. Besides, parametric simulations are conducted on the three-cell stack. It is found that the CO and H2 coverage varies between cells in the stack due to the temperature distribution difference, and the stack with more cells as well as the middle-cell of multi-cell stack have better performance, higher H2 coverage, lower CO coverage due to higher internal temperature. However, too high local temperature not only reduce the CO coverage but reduce the H2 coverage and increase the anode overpotential. The resistance to CO poisoning can be improved by increasing operating temperature, but when CO2 and water vapor are introduced into the anode, the H2 coverage decreases and the CO coverage increases due to the decrease of H2 concentration. The study clearly demonstrated that high performance and high CO resistance can be achieved by carefully regulating the operating conditions.

As a rising star, the fuel cell will be applied very broadly. However, when the fuel cell works at a high current, too much water yield and the redundancy water block the air or oxygen enter the fuel cell, then the power reduces sharply. The gas diffusion layer (GDL) in the fuel cell is the critical component to transfer water and gas. A novel GDL was prepared in this paper to improve transferability. The new GDL consists of one carbon paper and two microporous layers. The microporous layer close to carbon paper is modified by pore-former CaCO3. The total thickness of the new GDL is 270 μm; then, the samples were pressed to 220, 240, and 260 μm by rolling, respectively. The electrochemical impedance spectroscopy tests at a large current (2.5 A/cm2) show that the fuel cell with 240 μm GDL has relatively small transmission impedance regardless of high or low humidity. The results show that the new GDL can significantly improve the water transferability of the proton exchange membrane fuel cell.

Proton exchange membrane fuel cell (PEMFC), as an attractive alternative power source, has seen its increasing deployment in both automotive and small stationary applications. To improve the durability of the PEMFC system, recent research has engaged in developing prognostics and health management methods. Although the prognostics methods have been extensively studied to improve the prediction accuracy, some critical issues have not been fully addressed. For example, few studies have looked into the prognostics methods by different criteria and under dynamic operation conditions, and none of them have investigated the data availability and quality for PEMFC prognostics. Due to the lack of more comprehensive and general prognostics methods as well as the limitations in data, studies in the post-prognostics decision-making phase have hardly ever been initiated. This paper tends to provide a full review of the existing prognostics research by analysing the prognostics scales, horizon, threshold, and the use of methods. The data used in the previous studies has also been investigated. Moreover, four principal directions of post-prognostics decision-making have been proposed and discussed. According to the findings, research challenges and development perspectives in the aspects of data, prognostics and decision-making are proposed.

Fault diagnosis technology has been developed to improve the reliability of fuel cell systems in pursuit of successful commercialization. In this study, a hybrid fault diagnosis method is proposed to improve diagnosable fault magnitudes and diagnostic accuracy. Six types of faults in the air supply system of a proton exchange membrane fuel cell system were therefore defined and diagnosed according to the relevant components and locations as actuator, sensor, and piping faults. The proposed method applies an artificial neural network classifier as a data-based diagnostic tool within a model-based diagnosis method that relies upon residual patterns to address the limitations of the model-based diagnosis method (insufficient accuracy for initial fault diagnosis) and the data-based diagnosis method (need for a large dataset to generate a classifier). The proposed method is shown to improve the diagnostic accuracy and decrease the diagnosable fault magnitude compared to solely model-based and data-based methods. Moreover, the proposed method enables a faster diagnosis of air supply system faults, preventing loss of system efficiency and stack degradation. By providing fast and accurate diagnoses, the proposed method is expected to help develop an effective fuel cell health management system.

Incorporating inorganic fillers, such as SiO2, TiO2, and CeO2, into the electrolyte membrane via the conventional casting and evaporation process is proved to intensify the water retention, thus improve the proton conductivity of the polymer electrolyte membrane (PEM) under high temperature. However, this approach does not dramatically enhance the performance of the composite membrane due to the issue of proton pathway reduction and fillers agglomeration. Herein, uniformly patterned mesoporous TiO2 microplates (PTMPs) are successfully embedded on the anode side surface of the Nafion® membrane by using micro-hole stencil for spatially localizing the PTMPs and well-controlled ionomer spray technique. Interestingly, the membrane comprised of PTMPs with a diameter of ∼50 μm and a height of ∼5.2 μm exhibits the maximum power density by more than 35.2% compared to the reference Nafion® membrane with the same thickness (∼25 μm) under 120 °C and relative humidity of 35% condition. The result indicates that suitably designed PTMPs-embedded Nafion® membrane is effective for improving the PEMFC performance under elevated temperature and low humidity conditions.

A high advancement has been achieved in the design of proton exchange membrane fuel cells (PEMFCs) since the development of thin-film catalyst layers (CLs). However, the progress has slowed down in the last decade due to the difficulty in reducing Pt loading, especially at the cathode side, while preserving high stack performance. This situation poses a barrier to the widespread commercialization of fuel cell vehicles, where high performance and durability are needed at a reduced cost. Exploring the technology limits is necessary to adopt successful strategies that can allow the development of improved PEMFCs for the automotive industry. In this work, a numerical model of an optimized cathode CL is presented, which combines a multiscale formulation of mass and charge transport at the nanoscale (∼10nm) and at the layer scale (∼1μm). The effect of exterior oxygen and ohmic transport resistances are incorporated through mixed boundary conditions. The optimized CL features a vertically aligned geometry of equally spaced ionomer pillars, which are covered by a thin nanoporous electron-conductive shell. The interior surface of cylindrical nanopores is catalyzed with a Pt skin (atomic thickness), so that triple phase points are provided by liquid water. The results show the need to develop thin CLs with bimodal pore size distributions and functionalized microstructures to maximize the utilization of water-filled nanopores in which oxygen transport is facilitated compared with ionomer thin films. Proton transport across the CL must be assisted by low-tortuosity ionomer regions, which provide highways for proton transport. Large secondary pores are beneficial to facilitate oxygen distribution and water removal. Ultimate targets set by the U.S. Department of Energy and other governments can be achieved by an optimization of the CL microstructure with a high electrochemical surface area, a reduction of the oxygen transport resistance from the channel to the CL, and an increase of the catalyst activity (or maintaining a similar activity with Pt alloys). Carbon-free supports (e.g., polymer or metal) are preferred to avoid corrosion and enlarge durability.

The ordered membrane electrode assembly (MEA) is currently the frontier research field of proton exchange membrane fuel cells (PEMFCs). The ordered MEA is effective in increasing the utilization of...

Proton exchange membrane (PEM) water electrolyzers are a key technology in decarbonizing hydrogen production. Though the market for PEM electrolyzer systems is growing, there are concerns that the ...