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The three-dimensional Ni redox-active metal-organic framework [Ni(bpy)(fcdHp)] based on nickel(ii) cations, anions of ferrocenylbis(H-phosphinic) acid (H2fcdHp), and 4,4′-bipyridine (bpy) was first tested as an oxygen reduction reaction (ORR) catalyst. This compound showed remarkable efficiency and good stability under electrochemical conditions. The diagnostic performance in a proton-exchange membrane fuel cell with this catalyst on the cathode side of the membrane-electrode assembly (MEA) was evaluated for the first time. The catalytic ability of the new system as an ORR catalyst without a platinum catalyst on the anode side was confirmed in a half-cell setup, in which the cathode compartment of the MEA and the anode (liquid electrochemical cell) are separated by a polyelectrolyte membrane. [ABSTRACT FROM AUTHOR]

Fuel cell electric vehicles (FCEVs) are among the devices that have emerged in recent years. To provide electricity to the electric motors, they use a proton-exchange membrane fuel cell (PEMFC) as the primary energy source and a secondary source consisting of an energy storage system (battery or supercapacitors). The addition of these sources to the motors and accessories of a vehicle requires the association of static converters to condition the different power sources. In addition, a high-efficiency and enhanced-reliability power converter is essential to connect the PEMFC to the vehicle's DC bus. This paper proposes a robust feedback controller for a four-phase interleaved boost converter used with PEMFC. The proposed controller has double loops based on a state-feedback controller, and an inner loop which translates the differential equation of the system into a state representation by linearization around its operation points. The reference current is generated by state feedback in the outer loop; the state variable is defined by using a change variable. The strong robustness and highly dynamic characteristics of the proposed controller are demonstrated through its performance in terms of output voltage, source current, and settling time. The findings indicate that the proposed controller achieves a response time of 20 ms, resulting in an over 50 % improvement compared to the controllers referenced in the literature. Additionally, it reduces both current and voltage ripple, keeping them each below 10 % . Further, the controller gains synthesis is validated using the linear quadratic regulator (LQR) technique as well as boundary conditions, and its robustness is verified, taking into account the uncertainty of various operating conditions and discrepancies in circuit components. A double-loop super-twisting sliding mode controller, a backstepping control algorithm, and a PI controller are selected for comparison and discussion. Subsequently, the effectiveness of the proposed controller is evaluated through simulation with the parameters of a 500 W fuel cell system. [ABSTRACT FROM AUTHOR]

The design of low-cost and high-performance anodic electrocatalyst is essential in proton exchange membrane water electrolysis (PEMWE) application. Herein, we design and synthesize a core–shell structure with Ir-rich shell and AuIr alloy core by using a simple liquid phase reduction method, which exposed a large number of active sites. The d-band center of Ir active sites, merely 2 nm in size, was shifted by the electronegativity difference between the Au and Ir atoms at the core–shell interface. The strong electronic effect can inhibit the dissolution and corrosion of Ir active sites under acidic and high potential conditions. As a result, Irx@Au0.25Ir0.75−x catalyst shows merely 235 mV overpotential at the current density of 10 mA cm−2, 75 mV lower than the commercial Ir black catalyst, and 2.6-fold higher mass activity than the commercial Ir black catalyst. Furthermore, when Irx@Au0.25Ir0.75−x was used as the anionic catalyst, the electrolysis voltage at 1 A cm−2 is 1.7 V in PEMWE, and this activity was maintained for more than 100 h and had exhibited excellent stability, indicating its ideal prospects as an electrocatalyst. AuIr alloy with Ir-rich core and AuIr alloy shell exposed numerous active sites and improved the utilization efficiency of electrocatalyst. [ABSTRACT FROM AUTHOR]

In this paper, the PANI/PDA-Ti4O7 composite coating was prepared on 316L by constant current deposition with a current density of 2.8 mA·cm−2, in which the Ti4O7 powders were modified by PDA (polydopamine). The open-circuit potential of the obtained PANI/PDA-Ti4O7 composite coating is about 365 mVAg/AgCl, which is more positive than that of the bare 316L. During immersion in 1 M H2SO4 + 2 ppm HF for 200 h, the high stable corrosion potential and the lower Rf indicate that the composite coating has long-term corrosion resistance. [ABSTRACT FROM AUTHOR]

Acid‐functionalized polymers enhance the performance of phosphoric‐acid‐doped polybenzimidazoles (PA/PBIs); however, studies on examining the mechanisms driving these enhancements are scarce. Furthermore, the nanophase morphology of PA‐dependent proton‐exchange membranes has been rarely explored, despite its direct role in the distribution of PA and protonic conduction. In this study, theoretical and experimental analyses to evaluate the microphase separation, particularly the formation and in situ transformation of a two‐phase interface, in a defect‐free polyphenylene ionomer (SPP‐QP) with excellent integrity are performed. SPP‐QP serves as a fortifying agent with an enhanced microphase‐separation ability within PA/PBI‐based membranes. Specifically, the distinct swelling behavior of PA results in the formation of PA‐rich and PA‐poor regions. Thus, the formation of a durable interface that is impervious to PA degradation between SPP‐QP and PBI is critical for facilitating microphase separation. A single cell composed of the composite membrane offers a peak power density of 719 mW cm−2 at 160 °C. Moreover, the durability of a single cell is much longer than 150 h. The results obtained in this study provide insights into the micromorphology and membrane properties observed in the presence of PA. [ABSTRACT FROM AUTHOR]

Proton-exchange membrane fuel cells (PEMFCs) are critical components of zero-emission electro-hydrogen generators. Accurate performance prediction is vital to the optimal operation management and preventive maintenance of these generators. Polarization curve remains one of the most important features representing the performance of PEMFCs in terms of efficiency and durability. However, predicting the polarization curve is not trivial as PEMFCs involve complex electrochemical reactions that feature multiple nonlinear relationships between the operating variables as inputs and the voltage as outputs. Herein, we present an artificial-intelligence-based approach for predicting the PEMFCs’ performance. In that way, we propose first an explainable solution for selecting the relevant features based on kernel principal component analysis and mutual information. Then, we develop a machine learning approach based on XGBRegressor and Bayesian optimization to explore the complex features and predict the PEMFCs’ performance. The performance and the robustness of the proposed machine learning based prediction approach is tested and validated through a real industrial dataset including 10 PEMFCs. Furthermore, several comparison studies with XGBRegressor and the two popular machine learning-based methods in predicting PEMFC performance, such as artificial neural network (ANN) and support vector machine regressor (SVR) are also conducted. The obtained results show that the proposed approach is more robust and outperforms the two conventional methods and the XGBRegressor for all the considered PEMFCs. Indeed, according to the coefficient of determination criterion, the proposed model gains an improvement of 6.35%, 6.8%, and 4.8% compared with ANN, SVR, and XGBRegressor respectively.

A model for a fuel cell propelled 50 PAX hydrogen aircraft is developed. In terms of year 2045 Nordic air travel demand this aircraft is expected to cover 97% of travel distances and 58% of daily passenger volume. Using an ATR 42 as a baseline, cryogenic tanks and fuel cell stacks are sized and propulsion system masses updated. Fuselage and wing resizing are required, which increases mass and wetted area. Sizing methods for the multi-stack fuel cell and the cryogenic tanks are implemented. The dynamic aircraft model is updated with models for hydrogen consumption and tank pressure control. For the Multi-layer insulation (MLI) tank a trade study is performed. A ventilation pressure of 1.76 bar and 15 MLI layers are found to be optimal for the design mission. A return-without-refuel mission is explored, where for a 10-hour ground hold 38.4% of the design range is retained out of the theoretically achievable 50%. [Display omitted] • A 50 PAX hydrogen aircraft is designed to meet year 2045 Nordic air travel demand. • An optimal tank design is found by trading insulation against ventilation pressure. • Higher than optimal ventilation pressure excels in return-without-refuel mission. • Tank gravimetric index has little effect on short-range fuel cell aircraft's H 2 use. • Boil-off ventilation is the main driving factor in design mission H 2 consumption. [ABSTRACT FROM AUTHOR]

The proton-exchange membrane fuel cell (PEMFC) is one of the important technologies advancing sustainable energy. However, predicting its performance and optimizing processes is challenging due to the complexity of integrating various types of data with interdependent variables. This study introduces a novel deep learning model using multimodal data that integrated convolutional neural networks (CNN) and deep neural networks (DNN) to address these challenges. The proposed model predicts the performance through the CNN model using cell images taken from the optical microscope, and based on this, generates multimodal data to predict the optimal process conditions for each performance through the DNN model. Trained on a diverse array of experimental data under various conditions, our model significantly enhances the reliability of performance predictions and optimal process determinations, evidenced by an R2 value of 0.83. Unique to this research, the AI model utilizes both PEMFC cell images and performance data, enabling automatic performance prediction and substantially reducing the need for individual cell measurements. By analyzing both morphological images and experimental data, our model accurately predicts optimal process conditions, overcoming previous integration challenges. This method not only facilitates the performance assessment process but also optimizes manufacturing operations, thereby increasing efficiency and production rates in PEMFC manufacturing.

Fuel cell electric vehicles (FCEVs) are among the devices that have emerged in recent years. To provide electricity to the electric motors, they use a proton-exchange membrane fuel cell (PEMFC) as the primary energy source and a secondary source consisting of an energy storage system (battery or supercapacitors). The addition of these sources to the motors and accessories of a vehicle requires the association of static converters to condition the different power sources. In addition, a high-efficiency and enhanced-reliability power converter is essential to connect the PEMFC to the vehicle’s DC bus. This paper proposes a robust feedback controller for a four-phase interleaved boost converter used with PEMFC. The proposed controller has double loops based on a state-feedback controller, and an inner loop which translates the differential equation of the system into a state representation by linearization around its operation points. The reference current is generated by state feedback in the outer loop; the state variable is defined by using a change variable. The strong robustness and highly dynamic characteristics of the proposed controller are demonstrated through its performance in terms of output voltage, source current, and settling time. The findings indicate that the proposed controller achieves a response time of 20 ms, resulting in an over 50% improvement compared to the controllers referenced in the literature. Additionally, it reduces both current and voltage ripple, keeping them each below 10%. Further, the controller gains synthesis is validated using the linear quadratic regulator (LQR) technique as well as boundary conditions, and its robustness is verified, taking into account the uncertainty of various operating conditions and discrepancies in circuit components. A double-loop super-twisting sliding mode controller, a backstepping control algorithm, and a PI controller are selected for comparison and discussion. Subsequently, the effectiveness of the proposed controller is evaluated through simulation with the parameters of a 500 W fuel cell system.

The performance and durability of proton‐exchange membrane fuel cells (PEMFCs) are constrained by fuel delivery and water management. Based on parallel and serpentine flow fields, the effects of triangular baffles (30°, 45°, and 60°) and conical runners (1°, 2°, and 3°) on the performance output of PEMFC at different angles are studied. The three‐dimensional and multi‐phase models are established by using the simulation software package (ANSYS FLUENT). The findings demonstrate that the battery's output performance reaches its peak when the baffle angle is set at 45°. When the output current density is 0.7 A/cm2, the power density of the 45° baffle increases by 18.87%. The pressure loss is not only lower than that of the 60° baffle but also exhibits no significant difference when compared to the 30° baffle. In addition, the introduction of conical channels has enhanced the output performance of PEMFCs in comparison to the traditional serpentine flow field. The power density of the 2°tapered channel exhibits a 12.65% increase when the output current density reaches 0.8 A/cm2. However, the performance output of the 3°tapered channel is inferior to that of the conventional serpentine flow field. [ABSTRACT FROM AUTHOR]

In the paper, electrochemical behavior of platinum based cathode catalyst in a polymer electrolyte membrane fuel cell is studied under non-symmetric square-wave electric potential cycling applied in accelerated stress test. Following the modeling by Holby and Morgan, degradation due to Pt dissolution, ion diffusion, and oxide coverage is performed with respect to cycling operating conditions and model parameters. The computer simulation demonstrates impact of the electrochemical surface area loss rate under variation of the temperature, pH, platinum particle diameter, loading, Pt to Carbon volume fraction, and their simultaneous effect. From physical consistency and multi-parametric sensitivity analysis, a statement on feasible domain of the parameters for the PEMFC operation is concluded. • Holby–Morgan model of platinum electrochemical degradation in PEMFC is applied. • The catalyst degradation is calculated under EU FCH 2JU AST cycling protocol. • ECSA ratio loss rate is correlated with operating conditions and model parameters. • Sensitivity analysis gives feasible range of multiple variable parameters. • Temperature, pH, Pt particle diameter, loading, and Pt/C volume fraction are tested. [ABSTRACT FROM AUTHOR]

Gas diffusion layers (GDLs) in high-temperature, high-humidity, and high-electric-potential environments can be affected by the carbon corrosion and degradation of Polytetrafluoroethylene (PTFE) network structures, resulting in reduced reliability and hydrophobicity. By using cyclic voltammetry and offline characterization, a high-potential scanning of 1–1.5 V is applied to the GDL in the three-electrode system, considering the role of gradient graphitization degree and pore size structure in corrosion. Accelerating the electrochemical corrosion process of carbon and PTFE allows the identification of corrosion location, extent, and determinants. The results indicate that after 800 cycles of high-potential triangulation scanning, the graphitization of gas diffusion base has the most significant impact on the GDL's durability. On the other hand, the durability of the GDL's microporous layer is influenced by its small pore size structure rather than its graphitization degree. Furthermore, the corrosion process of GDLs with a small pore size structure tends to be relatively slow, providing a basis for GDL selection and durability prediction. [ABSTRACT FROM AUTHOR]

Loss of electrochemical surface area in proton-exchange membrane is of large practical importance, since membrane degradation largely affects the durability and life of fuel cells. In this paper, the electrokinetic model developed by Holby and Morgan is considered. The paper describes degradation mechanisms in membrane catalyst presented by platinum dissolution, platinum diffusion, and platinum oxide formation. A one-dimensional model is governed by nonlinear reaction–diffusion equations given in a cathodic catalyst layer using Butler–Volmer relationships for reaction rates. The governing system is endowed with initial conditions, mixed no-flux boundary condition at the interface with gas diffusion layer, and a perfectly absorbing condition at the membrane boundary. In cyclic voltammetry tests, a non-symmetric square waveform is applied for the electric potential difference between 0.6 and 0.9 V held for 10 and 30 s, respectively, according to the protocol of European Fuel Cell and Hydrogen Joint Undertaking. Aimed at mitigation strategies, the impact of cycling operating conditions and model parameters on the loss rate of active area is investigated. The global behavior with respect to variation of parameters is performed using the method of sensitivity analysis. Finding feasible and unfeasible values helps to determine the range of test parameters employed in the model. Comprehensive results of numerical simulation tests are presented and discussed. [ABSTRACT FROM AUTHOR]

The focus in the development of catalysts doped with transition metals aims to replace platinum group metal catalysts in fuel cells. However, these non-precious metal catalysts exhibit limited performance in acidic environment for the oxygen reduction reaction (ORR) due to issues such as metal agglomeration and the subsequent loss of active sites. Herein, we synthesised catalysts doped with iron and nitrogen on a composite material consisting of carbide-derived carbon (CDC) and graphene (G), employing an additional nitrogen source dicyandiamide (DCDA), denoted as FeN-CDC/G/DCDA. Our physico-chemical analysis unveiled that the inclusion of DCDA was effective in mitigating metal agglomeration during the synthesis process and increasing the presence of Fe-Nx sites in the catalysts. Notably, the FeN-CDC/G/DCDA catalyst exhibited enhanced ORR activity in acid media with half-wave potential (E1/2) of 0.76 V, surpassing the performance of the FeN-CDC/G catalyst, which had an E1/2 value of 0.70 V. Furthermore, the rotating ring-disk electrode results indicated a reduced formation of hydrogen peroxide when employing the FeN-CDC/G/DCDA catalyst. The findings from this study represent a significant step towards the development of efficient catalysts for fuel cells, underscoring the pivotal role of additional nitrogen doping and its positive impact on the ORR performance.

The electrode ionomer plays a crucial role in the catalyst layer (CL) of a proton-exchange membrane fuel cell (PEMFC) and is closely associated with the proton conduction and gas transport properties, structural stability, and water management capability. In this review, we discuss the CL structural characteristics and highlight the latest advancements in ionomer material research. Additionally, we comprehensively introduce the design concepts and exceptional performances of porous electrode ionomers, elaborate on their structural properties and functions within the fuel cell CL, and investigate their effect on the CL microstructure and performance. Finally, we present a prospective evaluation of the developments in the electrode ionomer for fabricating CL, offering valuable insights for designing and synthesizing more efficient electrode ionomer materials. By addressing these facets, this review contributes to a comprehensive understanding of the role and potential of electrode ionomers for enhancing PEMFC performance. [ABSTRACT FROM AUTHOR]

Organic-inorganic composite membranes are used in various applications, especially as proton-conducting electrolyte membranes for proton-exchange membrane fuel cells (PEMFCs). This study proposed a method to fill a flexible porous substrate solely with high amounts of inorganic (approximately 48 wt%) nano-zirconia precursor, surface-modified by acetylacetone (AcAc-Zr). AcAc-Zr can be converted to zirconium phosphate (ZrPi) in situ, and several other zirconium phosphonates, such as zirconium aminotris-methylene-phosphonate (ZrATMP) and zirconium 1-hydroxyethane-1,1-diphosphonate (ZrHEDP). Transmission electron microscopy-energy dispersive spectroscopy (TEM-EDS) analysis revealed that the pores were continuously filled with ZrPi, indicating that ZrPi has a percolated structure in the membrane, beneficial for their proton conduction. The proton conductivities of the membranes, including ZrPi, ZrHEDP, and ZrATMP, were sufficiently high, on the order of 1 mS cm−1 at 80 °C and 95% relative humidity. • In situ conversion of the Zr precursor to various derivatives. • High-content zirconium phosphonates (ZrPi, ZrATMP, and ZrHEDP) were solely filled in porous substrates. • Inorganics in the membrane formed continuous pathways for proton conduction. [ABSTRACT FROM AUTHOR]

A Pt‐free cathode catalyst is necessary for proton‐exchange membrane fuel cell (PEMFC) to enable the widespread use of these environmentally friendly energy conversion devices at affordable price. Herein, a pyrolyzed electrospun carbon nanofibre (CNF) catalyst is prepared embedded with cobalt(II) phthalocyanine and iron(II) phthalocyanine compounds to provide the transition metal N4‐macrocyclic complex‐derived sites (MNX) possessing better electrocatalytic oxygen reduction reaction (ORR) activity. The physical characterisation showed the nanofibrous structure of catalyst with rough surface texture and considerable amount of N, Fe, and Co. The D−MN4−CNF−IL−A catalyst prepared using ionic liquid as a porogen displayed the best electrocatalytic activity for O2 electroreduction proceeding via 4e− pathway in 0.5 M H2SO4 electrolyte solution with the ORR onset and half‐wave potential of 0.83 and 0.71 V vs reversible hydrogen electrode (RHE), respectively. [ABSTRACT FROM AUTHOR]

Abstract A Pt‐free cathode catalyst is necessary for proton‐exchange membrane fuel cell (PEMFC) to enable the widespread use of these environmentally friendly energy conversion devices at affordable price. Herein, a pyrolyzed electrospun carbon nanofibre (CNF) catalyst is prepared embedded with cobalt(II) phthalocyanine and iron(II) phthalocyanine compounds to provide the transition metal N4‐macrocyclic complex‐derived sites (MNX) possessing better electrocatalytic oxygen reduction reaction (ORR) activity. The physical characterisation showed the nanofibrous structure of catalyst with rough surface texture and considerable amount of N, Fe, and Co. The D−MN4−CNF−IL−A catalyst prepared using ionic liquid as a porogen displayed the best electrocatalytic activity for O2 electroreduction proceeding via 4e− pathway in 0.5 M H2SO4 electrolyte solution with the ORR onset and half‐wave potential of 0.83 and 0.71 V vs reversible hydrogen electrode (RHE), respectively.

In the proton-exchange membrane fuel cell (PEMFC), the partial pressure equalization between hydrogen and oxygen is one of the most significant problems influencing PEMFC efficiency and lifetime. In this paper, an adaptive neural fuzzy inference system (ANFIS)-based pressure tracking controller for a PEMFC system is investigated under the variation of load current. The suggested controller is designed based on the dynamic model to enhance the efficiency and prolong the stack life of the PEMFC system. First, the pressure control system model is established on the premise of the electrochemical and react flow model. Next, the ANFIS controller is developed to further improve the transient performance and minimize the partial pressures of hydrogen and oxygen. Finally, the simulation and experimental results are provided to demonstrate the effectiveness of the suggested method. Compared to the super-twisting sliding mode controller (STSMC), the proposed ANFIS controller has increased the tracking performance by 89.5% in simulation and 72.06% in the experiment under the multi-step load current.

Loss of electrochemical surface area in proton-exchange membrane is of large practical importance, since membrane degradation largely affects the durability and life of fuel cells. In this paper, the electrokinetic model developed by Holby and Morgan is considered. The paper describes degradation mechanisms in membrane catalyst presented by platinum dissolution, platinum diffusion, and platinum oxide formation. A one-dimensional model is governed by nonlinear reaction–diffusion equations given in a cathodic catalyst layer using Butler–Volmer relationships for reaction rates. The governing system is endowed with initial conditions, mixed no-flux boundary condition at the interface with gas diffusion layer, and a perfectly absorbing condition at the membrane boundary. In cyclic voltammetry tests, a non-symmetric square waveform is applied for the electric potential difference between 0.6 and 0.9 V held for 10 and 30 s, respectively, according to the protocol of European Fuel Cell and Hydrogen Joint Undertaking. Aimed at mitigation strategies, the impact of cycling operating conditions and model parameters on the loss rate of active area is investigated. The global behavior with respect to variation of parameters is performed using the method of sensitivity analysis. Finding feasible and unfeasible values helps to determine the range of test parameters employed in the model. Comprehensive results of numerical simulation tests are presented and discussed.

Proton-exchange membrane fuel cells (PEMFCs), as potential energy converters with broad application prospects, have low durability owing to several factors that make it difficult to quantify the degradation of PEMFC components. The accurate prediction of the remaining useful life (RUL) can help users understand the degradation status of PEMFCs and adopt reasonable maintenance strategies to improve durability. This paper proposes an RUL prediction framework based on a temporal convolutional network (TCN). First, an equivalent circuit model of the PEMFC is established, and complex nonlinear least squares regression is used to fit the model to estimate the polarization resistance. Then, the prediction framework and joint degradation indicator of the TCN are constructed to predict the RUL. The TCN is compared with four models: linear regression, Holt–Winters, seasonal autoregressive integrated moving average, and Prophet. The results show that the TCN performs significantly better in terms of all the predictive metrics, including the root-mean-squared error which is at least 13.43% lower than those of the four models. The RUL prediction accuracy of the TCN is at least 7.76% higher than that of the four models. Except at 800 h, the average RUL accuracy of TCN is 92.20%. This confirms that the TCN (double variables) can accurately predict the RUL of PEMFCs. [ABSTRACT FROM AUTHOR]

Enhancing the cold start ability of proton-exchange membrane fuel cells (PEMFCs) can widely apply fuel cells in a cold environment. In this study, PEMFC cold start performance was significantly affected by penetrating holes in a cathode micro-diffusion layer (MDL). The testing MDLs were mechanically processed with 0.2-mm-diameter and 0.5-mm-diameter penetrating holes, respectively, and the normal MDL as reference. Fundamental water permeance and PEMFC performance tests at normal temperature were conducted beforehand for all MDLs. The cold start of the fuel cell was experimentally studied by monitoring PEMFC voltage and high-frequency impedance. Results show that the 0.5-mm-diameter penetrating holes improve the water permeance at least three orders of magnitude than the normal MDL. The fuel cell using the MDL with the 0.2-mm-diameter penetrating holes performs best in regular operation at 70 °C and in cold starts from −7 °C. • Penetrating holes are designed in a PEMFC cathode micro-diffusion layer. • Penetrating holes skyrocket the water permeance of the micro-diffusion layer. • High-frequency impedance characterizes the icing process. • Penetrating holes prolong the initial freezing time. • Moderate hole size achieves a smooth cold start at lower temperatures. [ABSTRACT FROM AUTHOR]

The present study proposes a new optimal arrangement for a combined cooling, heating, and power (CCHP) system based on a proton-exchange membrane (PEM) fuel cell. The system is designed to supply the energy required by the households. The main purpose of this paper is to provide this configuration by considering several optimal parameters including exergy, energy, GHG reduction, and annual cost. The system is optimized by a newly developed metaheuristic, called fractional‑order search and rescue (FO-SAR) optimizer to minimize the annual cost and to maximize the economic efficiency of the CCHP system. The suggested system is then analyzed in different terms and a comparison of its results with two other methods including the original search and rescue (FO-SAR) optimizer and the NSGA-II is performed to show the effectiveness of the proposed system in different terms. [ABSTRACT FROM AUTHOR]

The gas diffusion layer (GDL) is composed of a microporous layer (MPL) and a substrate; this substrate is generally fabricated from carbon fiber, carbonized resin, and polytetrafluoroethylene. When the MPL penetrates deeper into the substrate, the porosity and pore size of the GDL decrease, and the tortuosity increases; this leads to a reduction in the water discharge capability of the GDL. In this study, the MPL penetration ratio over the total GDL thickness was controlled using three different substrate manufacturing methods. These manufacturing methods for preventing the MPL from penetrating deeper into the substrate were based on the carbon fiber content within the substrate, the amount of carbonized resin coating on the substrate, and the approach used for loading the MPL. Furthermore, the GDLs were manufactured at different carbonization temperatures to investigate the effects of the carbonization temperature of the substrate on the performance of the proton-exchange membrane fuel cell. [ABSTRACT FROM AUTHOR]

Sodium pectate derivatives with 25% replacement of sodium ions with nickel ions were obtained by carbonization to temperatures of 280, 550, and 800 °C, under special protocols in an inert atmosphere by carbonization to temperatures of 280, 550, and 800 °C. The 25% substitution is the upper limit of substitution of sodium for nickel ions, above which the complexes are no longer soluble in water. It was established that the sample carburized to 550 °C is the most effective active element in the hydrogen-oxidation reaction, while the sample carbonized up to 800 °C was the most effective in the oxygen-reduction reaction. The poor performance of the catalytic system involving the pectin coordination biopolymer carbonized up to 280 °C was due to loss of proton conductivity caused by water removal and mainly by two-electron transfer in one catalytic cycle of the oxygen-reduction reaction. The improved performance of the system with coordination biopolymer carbonized up to 550 °C was due to the better access of gases to the catalytic sites and four-electron transfer in one catalytic cycle. The (Ni-NaPG)800C sample contains metallic nickel nanoparticles and loose carbon, which enhances the electrical conductivity and gas capacity of the catalytic system. In addition, almost four-electron transfer is observed in one catalytic cycle of the oxygen-reduction reaction.

This work explores a novel and sustainable synthesis strategy for developing platinum-group metal (PGM)-free catalysts with high electrocatalytic activity, emphasizing the significance of hierarchically porous structures to improve electrocatalytic performance. We present an easily scalable method that utilizes magnesium salt as the precursor of sacrificial template to synthesize mesoporous carbon-based catalysts. The catalysts are doped with nitrogen and iron, while manganese is added to increase the stability of the catalyst under highly corrosive acidic conditions. The electrochemical oxygen reduction reaction (ORR) is investigated in acidic media using the rotating disk electrode technique. The electrocatalytic activity of the prepared catalysts is evaluated in proton exchange membrane fuel cell (PEMFC), where a significant increase in performance is achieved with the hierarchically porous carbon catalyst. The results demonstrate the potential of these catalysts as efficient and durable alternatives to PGM-based cathode catalysts in PEMFCs. [Display omitted] • Mesoporous catalysts are prepared from alkylresorcinols using an Mg-based template. • High ORR activity of Fe- and FeMn-doped M-N-C catalysts in RDE test in acidic media. • FeMn-doped electrocatalyst exhibits increased stability in AST and low H 2 O 2 yield. • Excellent PEMFC results were obtained using PGM-free materials as cathode catalysts. [ABSTRACT FROM AUTHOR]

• Bimetallic PGM-free ORR electrocatalysts derived from ZIF-8 and MWCNT composite. • Catalysts exhibit high ORR activity and good selectivity with low H 2 O 2 yield. • Catalysts possess hierarchical porous structures and high specific surface area. • Catalysts delivered good peak power density (787 mW cm−2) in PEMFC conditions. • Catalysts showed good electrochemical stability in acid media (∆ E 1/2 = 5–20 mV). Non-precious metal catalysts are ideal low-cost substitutes of Pt/C for the sluggish oxygen reduction reaction (ORR), despite the serious stability challenges in proton exchange membrane fuel cells (PEMFC) to alleviate the energy crisis and environmental problems. Platinum group metal (PGM)-free bimetallic composite electrocatalysts are assumed to be an interesting route to be investigated to address the stability and ORR selectivity related issues in PEMFC conditions. In this regard, we propose a simple and facile synthesis route by a composite of multi-walled carbon nanotubes and zeolitic imidazolate framework (ZIF)-8 followed by impregnating dual transition metals (FeMn, FeCo, and CoMn) and evaluate their ORR activity in acid media and PEMFC performance. Various catalyst materials are prepared and optimized to achieve the highest electrocatalytic performance. The prepared catalysts are characterized by various physico-chemical methods to elucidate their textural, structural, and morphological properties. The high ORR electrocatalytic activity and selectivity of the catalyst are reported in terms of half-wave potential and low H 2 O 2 yield as determined by the rotating ring-disk electrode method. The significant electrochemical stability under accelerated durability test and high peak power density (787 mW cm−2) in H 2 -O 2 PEMFC made these catalysts as potential candidates for efficient alternatives to PGMs in the fuel cell cathodes. [Display omitted] [ABSTRACT FROM AUTHOR]

The water contents at both the anode and cathode of PEMFCs depend on the water-transport mechanism at the membrane. The humidity at the outside layers of the membrane determines the diffusion of water through it. The operating temperatures and pressures regulate the humidity conditions in the system. Because these parameters are nonlinear, the water-transport mechanism is analyzed via the difference in the water concentration on each side of the membrane. In this work, an experimental configuration is designed to investigate the diffusion mechanism of water through the membrane. A flat membrane module is tested in an isothermal test chamber to test the influence of temperature on the water-absorption and -transport characteristics of Nafion 117 and Nafion 211 membranes. A parametric study is conducted to test the water-transport mechanism at an operating pressure of 1 bar; temperatures of 30 °C, 50 °C, 70 °C and 90 °C; and a relative humidity ranging from 10% to 100%. The results indicate that the water content of Nafion 211 is higher than that of Nafion 117. The water content and diffusion coefficient are proportional to the operating temperature. In addition, the diffusion coefficient reaches its peak at conditions of 1 bar, 100% humidity, and 90 °C for both membrane types. [ABSTRACT FROM AUTHOR]

N-doping and sulfonation is prepared on the reduced graphene oxide (rGO) support for PtNi nanoparticles (PtNi/S-(N)rGO) by a simple method of hydrothermal synthesis and thermal decomposition. The specific surface area increases from 180.7 m2/g of PtNi/rGo to 293.5 m2/g of PtNi/S-(N)rGO. The surface morphology shows wrinkles sites, which are separated by the sulfonated groups. The catalytic stability and efficiency are improved by the anchoring effect of sulfonated groups and evenly distribution of nanoparticles, respectively. The synergistic effect of N-doping and sulfonation can be in favor of catalytic efficiency by the increase of number of electron transfer. The half-wave potential of the PtNi/S-(N)rGO catalyst is up to 0.632 V, a small positive shift compared to the Pt/C catalyst. The durability of the PtNi/S-(N)rGO is 2.6 times higher than of the Pt/C catalyst after 5000 repeated cycles. The peak power of the PtNi/S-(N)rGO catalyst increased 37.5% compared to the Pt/C catalyst. Therefore, the stability and catalytic efficiency are improved by the PtNi/S-(N)rGO catalyst applied in proton exchange membrane fuel cell (PEMFC) compared to the commercial Pt/C catalyst. [ABSTRACT FROM AUTHOR]

Transition-metal complexes are candidates for replacing platinum and its combinations with other metals as catalysts for the hydrogen oxidation reaction (HOR) in proton-exchange membrane fuel cells (PEMFCs). The results of catalytic tests of bis(diphosphine) coordination complexes of nickel [Ni(PPh2NPh2)2]·2BF4 and [Ni(PPh2NBn2)2]·2BF4 in liquid-phase oxidation of hydrogen and as components of catalysts for the HOR in PEMFC are analyzed. It was found that the latter complex is a much more efficient catalyst for the HOR in PEMFC than the former. ESR studies demonstrated an increase in the difference between the hyperfine coupling constants on phosphorus nuclei on going from [Ni(PPh2NPh2)2] · 2BF4 to [Ni(PPh2NBn2)2]·2BF4. Significant morphological differences between the complexes on the atomically smooth surface of pyrolytic graphite were revealed by atomic force microscopy. [ABSTRACT FROM AUTHOR]

The harmful impacts of fossil-fuel-based engines on the environment have resulted in the development of other alternatives for different types of vehicles. Currently, batteries and fuel cells are being used in the automotive industry, while promising progress in the maritime and aerospace sectors is foreseen. As a case study in the aerospace sector, an unmanned aerial vehicle (UAV) was considered. The goal and the novelty of this study are in its analysis of the possibility of providing 960 W of power for a UAV with a weight of 14 kg using a hybrid system of a lithium-ion (Li-ion) battery and proton-exchange membrane fuel cell (PEMFC). The dynamic performance of the system was analyzed considering three different load profiles over time in an optimized condition. PEMFC was the main supplier of power, while the battery intervened when the power load was high for the PEMFC and the system demanded an immediate response to the changes in power load. Additionally, the impacts of the operating temperature and the C-rate of the battery were characterized by the state of the charge of the battery to better indicate the overall performance of the system. [ABSTRACT FROM AUTHOR]

Due to problems such as pores on surface-treated coatings, the corrosion resistance of pure titanium bipolar plates for proton-exchange membrane fuel cells can be further improved by increasing the corrosion resistance of pure titanium by using differential speed-rolling (DSR); however, these materials have not yet reached the standard requirements of bipolar plates (corrosion current density i corr ＜103 nA·cm−2). In this work, the corrosion resistance of pure titanium was improved by optimizing the DSR process while the strength was maintained. The best corrosion resistance of the DSR pure titanium was achieved when the roller speed ratio was 2, while i corr was 429 nA·cm−2 in a solution of 0.5 M H 2 SO 4 and 2 mg/L HF at room temperature. The formability of the DSR pure titanium for bipolar plates was verified. The optimal holding pressure range was 6.8–7.0 kN. • Effects of RSR, roller diameter, and RR on the properties of DSR pure titanium were studied. • i corr of the DSR pure titanium in a simulated battery environment was 429 nA·cm−2 when the RSR was 2. • The formability of the DSR pure titanium for bipolar plates of PEMFC was verified. [ABSTRACT FROM AUTHOR]

Concentrating active Pt atoms in the outer layers of electrocatalysts is a very effective approach to greatly reduce the Pt loading without compromising the electrocatalytic performance and the total electrochemically active surface area (ECSA) for the oxygen reduction reaction (ORR) in hydrogen-based proton-exchange membrane fuel cells. Accordingly, a facile, low-cost, and hydrogen-assisted two-step method is developed in this work, to massively prepare carbon-supported uniform, small-sized, and surfactant-free Pd nanoparticles (NPs) with ultrathin ∼3-atomic-layer Pt shells (Pd@Pt3L NPs/C). Comprehensive physicochemical characterizations, electrochemical analyses, fuel cell tests, and density functional theory calculations reveal that, benefiting from the ultrathin Pt-shell nanostructure as well as the resulting ligand and geometric effects, Pd@Pt3L NPs/C exhibits not only significantly enhanced ECSA, electrocatalytic activity, and noble-metal (NM) utilization compared to commercial Pt/C, showing 81.24 m2/gPt, 0.710 mA/cm2, and 352/577 mA/mgNM/Pt in ECSA, area-, and NM-/Pt-mass-specific activity, respectively; but also a much better electrochemical stability during the 10,000-cycle accelerated degradation test. More importantly, the corresponding 25-cm2 H2-air/O2 fuel cell with the low cathodic Pt loading of ∼ 0.152 mgPt/cm2geo achieves the high power density of 0.962/1.261 W/cm2geo at the current density of only 1,600 mA/cm2geo, which is much higher than that for the commercial Pt/C. This work not only develops a high-performance and practical Pt-based ORR electrocatalyst, but also provides a scalable preparation method for fabricating the ultrathin Pt-shell nanostructure, which can be further expanded to other metal shells for other energy-conversion applications. [ABSTRACT FROM AUTHOR]

Due to the objectives established by the European Union and other countries, hydrogen production will be a key technology in the coming decades. There are several starting materials and procedures for its production. All methods have advantages and disadvantages, and the improvements in their performance and decreases in operational costs will be decisive in determining which of them is implemented. For all cases, including for the storage and transport of hydrogen, membranes determine the performance of the process, as well as the operational costs. The present contribution summarizes the most recent membrane technologies for the main methods of hydrogen production, including the challenges to overcome in each case.

In this study, the proton conductivity enhancement mechanism of Nafion-- silica sulfuric acid (SSA) composite membranes was studied using the vibrating tip technique of atomic force microscopy. The Nafion--SSA composite membranes showed enhanced proton conductivity and thermal and mechanical properties compared to those of pristine Nafion. Among the selected different weight percentages of SSA, 1 wt% SSA had the highest values. The aim of this study was to understand how proton conductivity enhancement is related to structure and morphology. It was determined that the enhancement is related to a microscopic morphological structure, which is the separation of the hydrophilic ionic channel network and hydrophobic backbone. The morphologies of membranes of three different weight percentages were studied using noncontact mode atomic force microscopy, force--distance spectroscopy, and electrostatic force microscopy to understand the ionic domain structures. Several factors that influence the proton conductivity enhancement of the composite membranes were investigated, including water content, hydrophilicity, and ionic domain enhancement due to the interconnection of the SSA and ionomer. Among the different SSA weight percentages, the 1 wt% Nafion--SSA composite membrane demonstrated superior performance. It presented the highest energy dissipation, water content, and phase separation. This result implied that 1 wt% SSA optimally induced phase separation owing to the interaction with the sulfonic acid groups of the SSA and reorganization of the morphological structure compared with other weight percentages of Nafion--SSA composite membranes. [ABSTRACT FROM AUTHOR]

Metal hydrides are very much reported as a potential safe option for high-density hydrogen storage materials. A combined system of proton-exchange membrane hydrogen fuel cell (PEMFC) and metal hydride (MH) tanks is designed to investigate their characteristics and performances as hydrogen storage and stable power supply system. An AB5-type (LaCe)Ni5 material containing three MH tanks is selected for investigation. Endothermic dehydrogenation of metal hydride controls the hydrogen evolution rates during a discharging period, which reduces the risk of accidents. The MH tank charged at a 20°C water bath sustains and supplies hydrogen for a longer time of 240 min. The performances of the MH tank at a water bath of 20°C and 10-bar conditions correspond to the optimum condition of hydrogen storage at the MH tank of Pragma Industries. The performances of the combined system were investigated in different working conditions. The system sustains and supplies hydrogen to PEMFC for 240, 160, 130, and 110 min for the working loads of 250, 500, 1,000, and 2,000 W, accordingly. It is concluded that hydrogen consumption frequency increases for higher load demand.

The microstructure of the gas diffusion layer (GDL) influences the fuel cell performance significantly. A deeper understanding of the transport processes within the GDL is crucial for its optimisation. In this study, a porous microstructure of the gas diffusion layer is reconstructed stochastically, and the impact of the anisotropy parameter on transport properties is examined and determined by comparing it to experimental data. Subsequently, a series of GDLs with different binder and polytetrafluoroethylene (PTFE) volume fractions are reconstructed. A pore-scale model (PSM) simulation is employed to compute the anisotropic transport properties of the reconstructed model. The PSM result indicates that, as the binder and PTFE percentages increase, the in-plane and through-plane diffusivities decrease, while the electrical and thermal conductivities show non-monotonic evolution. The water distribution and the invasion process of liquid water into the reconstructed GDL is investigated using the multiple-relaxation-time lattice Boltzmann method (LBM). The result demonstrates the effect of binder and PTFE, on water penetration in the GDL with constant and reduced porosity. Furthermore, the optimal volume fractions of binder and PTFE are determined based on the PSM and LBM results. This comprehensive analysis contributes to a better understanding of the interplay between microstructure, transport properties, and water behaviour in GDLs, offering insights for optimisation of mass transport and water management of fuel cells. [Display omitted] • The GDL microstructure is stochastically reconstructed. • The impact of anisotropy parameter on the transport properties is studied. • The effective transport properties are computed using pore-scale modelling. • The lattice Boltzmann method is employed to investigate the liquid water dynamics. • The impact of binder and PTFE on transport properties is investigated. [ABSTRACT FROM AUTHOR]

An accurate model of a proton-exchange membrane fuel cell (PEMFC) is important for understanding this fuel cell’s dynamic process and behavior. Among different large-scale energy storage systems, fuel cell technology does not have geographical requirements. To provide an effective operation estimation of PEMFC, this paper proposes a support vector machine (SVM) based model. The advantages of the SVM, such as the ability to model nonlinear systems and provide accurate estimations when nonlinearities and noise appear in the system, are the main motivations to use the SVM method. This model can capture the static and dynamic voltage–current characteristics of the PEMFC system in the three operating regions. The validity of the proposed SVM model has been verified by comparing the estimated voltage with the real measurements from the Ballard Nexa® 1.2 kW fuel cell (FC) power module. The obtained results have shown high accuracy between the proposed model and the experimental operation of the PEMFC. A statistical study is developed to evaluate the effectiveness and superiority of the proposed SVM model compared with the diffusive global (DG) model and the evolution strategy (ES)-based model.

For further commercializing proton-exchange membrane fuel cells, it is crucial to attain long-term durability while achieving high performance. In this study, a strategy for modifying commercial Nafion membranes by introducing ultrathin multiwalled carbon nanotubes (MWCNTs)/CeO2 layers on both sides of the membrane was developed to construct a mechanically and chemically reinforced membrane electrode assembly. The dispersion properties of the MWCNTs were greatly improved through chemical modification with acid treatment, and the mixed solution of MWCNTs/CeO2 was uniformly prepared through a high-energy ball-milling process. By employing a spray-coating technique, the ultrathin MWCNTs/CeO2 layers were introduced onto the membrane surfaces without any agglomeration problem because the solvent rapidly evaporated during the layer-by-layer stacking process. These ultrathin and highly dispersed MWCNTs/CeO2 layers effectively reinforced the mechanical properties and chemical durability of the membrane while minimizing the performance drop despite their non-ion-conducting properties. The characteristics of the MWCNTs/CeO2 layers and the reinforced Nafion membrane were investigated using various in situ and ex situ measurement techniques; in addition, electrochemical measurements for fuel cells were conducted.

The proton-exchange membrane fuel cell is a promising power source for automobile industry because of its zero pollution. However, its stack structure always faces increased contact resistance caused by assembly errors, leading to substantial energy loss during the working period. To enhance its output performance, the influence of assembly errors on contact resistance is studied for proton-exchange membrane fuel cell. The mechanical simulation model of fuel cell assembly process is established to provide contact resistance distribution with different assembly errors. An improved global sensitivity analysis method is proposed to evaluate the influence coefficient of each assembly error term on contact resistance based on a series of randomized simulation data. The case study of a single-layer fuel cell demonstrates the proposed method achieves higher efficiency than traditional sensitivity analysis methods, and finds out key assembly errors in regard to reducing contact resistance. [ABSTRACT FROM AUTHOR]

Summary: Proton‐exchange membrane fuel cell (PEMFC) operation and performance degrade when particulate matter (PM) present in the reactant gas stream is collected in the porous structure of the gas diffusion layers (GDL). Interaction of PM carried by the gas stream and their capture efficiency by fibrous structure of GDLs is numerically investigated at various levels of relative humidity (RH) and different particle sizes. For small particles (sub‐micron sizes), the Brownian diffusion mechanism is dominant, while transitioning to interception and inertial impaction mechanisms occur as particle size increases (micron sizes or larger). It is found that high humidity levels result in higher diameter and lower density of PM, lower air density, and lower particle bounce due to the absorption of water vapor in the PM. Of these four effects, the first is the most important and the third is the least important. As humidity level is increased, particle capture efficiency decreases for small particles, but increases for large particles. The present study implies that a filter capable of removing large particles must be installed in the upstream reactant gas supply line to avoid the accumulation/clogging of PM in GDL structure. [ABSTRACT FROM AUTHOR]

The harmful impacts of fossil-fuel-based engines on the environment have resulted in the development of other alternatives for different types of vehicles. Currently, batteries and fuel cells are being used in the automotive industry, while promising progress in the maritime and aerospace sectors is foreseen. As a case study in the aerospace sector, an unmanned aerial vehicle (UAV) was considered. The goal and the novelty of this study are in its analysis of the possibility of providing 960 W of power for a UAV with a weight of 14 kg using a hybrid system of a lithium-ion (Li-ion) battery and proton-exchange membrane fuel cell (PEMFC). The dynamic performance of the system was analyzed considering three different load profiles over time in an optimized condition. PEMFC was the main supplier of power, while the battery intervened when the power load was high for the PEMFC and the system demanded an immediate response to the changes in power load. Additionally, the impacts of the operating temperature and the C-rate of the battery were characterized by the state of the charge of the battery to better indicate the overall performance of the system.

In order to improve the cold-start performance of the fuel cell vehicles, a rapid anode heating system is provided to enable the stack to quickly reach its optimal performance at low temperatures. In this study, a three-dimensional element model of plate-fin heat exchanger has been developed and used to study the effect of structural parameters of staggered fins on the hydrogen transport phenomena and heat transfer performance. A series of simulations were carried out to study the influence of different fin parameters on heat transfer performance. Good agreement is found by comparing the simulation values with the predicted values of the experimental correlation and the deviation is less than 10%. It is shown that fin length has the greatest impact on the thermal performance factor of the radiator, while the contribution of fin thickness is minimal. Experiments show that the maximum heat transfer capacity of the plate-fin heat exchanger reaches 900 W, and the performance of the stack is increased by about 15%. Through the sensitivity analysis of the structural parameters of the hydrogen preheater, the optimal parameter combination was obtained. This research provides guidance for the design of the preheater and plays an important role in improving the low-temperature durability of hydrogen fuel cell engines. [ABSTRACT FROM AUTHOR]

Developing a precise semiempirical mathematical model based on multi-nonlinear equations for the proton-exchange membrane fuel cell (PEMFC), which guarantees suitable and accurate simulation of the electrical characteristics of typical PEMFC stacks under various operating scenarios, is the main target of this study. The unknown parameters of the PEMFC model are extracted using a novel efficient optimization technique called coyote optimization algorithm (COA). To validate the effectiveness of the proposed COA-based PEMFC model, two different cases of seven and ten unknown parameters are performed on a commercial PEMFC taken from literature. The sum of squared errors (SSE) between the experimentally measured data and the corresponding computed ones is considered as the objective function. Besides, the effectiveness of the developed algorithm is validated under different operating conditions. Moreover, the results obtained by the application of the proposed COA have been compared with other recent optimization methods reported in the literature, and very competitive results have been provided. Furthermore, parametric and nonparametric statistical analyses are presented to evaluate the accuracy and viability of the developed COA-based PEMFC model. [ABSTRACT FROM AUTHOR]

Output voltage regulation of DC–DC converters has recently gained an increasing attention to face the many system nonidealities. The fast switching behavior is nonlinear time varying, the presence of model and measurement uncertainties, and large variations, are all inherited challenges. The aim of the present work is to design a robust nonlinear controller that ensures satisfactory and robust output voltage regulation for a proton-exchange membrane fuel cell (PEMFC) based on a DC–DC Interleaved Boost Converter (IBC). A state-space model of the DC–DC IBC is first derived using the state-space averaging technique, and a mathematical model is constructed for the PEFMC. In this regard, a robust nonlinear controller and a proportional integral controller are proposed. The controllers are tuned though particle swarm optimization algorithm to estimate their good parameters assuring the desired performance is met. The integral of absolute error criterion is used to improve the dynamic performance of the overall controlled system. Furthermore, the closed-loop stability is analyzed using the Lyapunov stability theorem, and the effectiveness of the closed-loop system is validated under various operating conditions of the PEMFC and load perturbations. Compared to other methods, the obtained results demonstrate a superior performance of the proposed control strategy in terms of its robustness to variations and uncertainties, smooth tracking of a varying set-point and faster transients. [ABSTRACT FROM AUTHOR]

Summary: Recently, highly porous metal foams have been used to replace the traditional open‐flow channels to improve gas transport and distribution in the cells. Deformation of flow plate, gas diffusion layer (GDL), and metal foam may occur during assembling. When the cell size is small, the deformation may not be significant. For large area cells, the deformation may become significant to affect the cell performance. In this study, an assembling device that is capable of applying uniform clamping force is built to facilitate fuel cell assembling and alleviate the deformation. A compressing plate that is the same size of the active area is used to apply uniform clamping force before surrounding bolts are fastened. Therefore, bending of the flow plate and deformation of GDL and metal foam can be minimized. Effects of the clamping force on the microstructures of GDL and metal foam, various resistances, pressure drops, and cell performance are investigated. Distribution of the contact pressure between metal foam and GDL is measured by using pressure sensitive films. Field‐emission scanning electron microscope is used to observe the microstructures. Electrochemical impedance spectroscopy analysis is used measure resistances. The fuel cell performance is measured by using a fuel cell test system. For the cell design used in this study, the optimum clamping force is found to be 200 kgf. Using this optimum clamping force, the cell performance can be enhanced by 50%, as compared with that of the cell assembled without using clamping plates. With appropriate clamping force, the compression force distribution across the entire cell area can approach uniform. This enables uniform flow distribution and reduces mass transfer resistance. Good contact between GDL and metal foam also lowers the interface resistance. All these factors contribute to the enhanced cell performance. [ABSTRACT FROM AUTHOR]