Performance Of Proton Exchange Membrane Fuel Cell Research Articles

Recent Progress in Materials Design and Fabrication Techniques for Membrane Electrode Assembly in Proton Exchange Membrane Fuel Cells

Proton Exchange Membrane Fuel Cells (PEMFCs) are widely regarded as promising clean energy technologies due to their high energy conversion efficiency, low environmental impact, and versatile application potential in transportation, stationary power, and portable devices. Central to the operation and performance of PEMFCs are advancements in materials and manufacturing processes that directly influence their efficiency, durability, and scalability. This review provides a comprehensive overview of recent progress in these areas, emphasizing the critical role of membrane electrode assembly (MEA) technology and its constituent components, including catalyst layers, membranes, and gas diffusion layers (GDLs). The MEA, as the heart of PEMFCs, has seen significant innovations in its structure and manufacturing methodologies to ensure optimal performance and durability. At the material level, catalyst layer advancements, including the development of platinum-group metal catalysts and cost-effective non-precious alternatives, have focused on improving catalytic activity, durability, and mass transport. Similarly, the evolution of membranes, particularly advancements in perfluorosulfonic acid membranes and alternative hydrocarbon-based or composite materials, has addressed challenges related to proton conductivity, mechanical stability, and operation under harsh conditions such as low humidity or high temperature. Additionally, innovations in gas diffusion layers have optimized their porosity, hydrophobicity, and structural properties, ensuring efficient reactant and product transport within the cell. By examining these interrelated aspects of PEMFC development, this review aims to provide a holistic understanding of the state of the art in PEMFC materials and manufacturing technologies, offering insights for future research and the practical implementation of high-performance fuel cells.

Optimizing the Coordination Energy of Co-Nx Sites by Co Nanoparticles Integrated with Fe-NCNTs for Boosting PEMFC and Zn-Air Battery Performance.

Enhancing the catalytic performance and durability of M-N─C catalyst is crucial for the efficient operation of proton exchange membrane fuel cells (PEMFCs) and Zn-Air batteries (ZABs). Herein, an approach is developed for the in situ fabrication of a MOFs-derived porous carbon material, co-loaded with Co nanoparticles (NPs) and Co-Nx sites and integrated onto Fe-doped carbon nanotubes (CNTs), named CoNP/SA-NC/Fe-NCNTs. Incorporating polymer-wrapped CNTs improves MOFs dispersion annealing at high temperature, which amplifies the three-phase boundary (TPB) by generating much more mesopores and exposing additional active sites within the catalysts layer. Furthermore, density functional theory (DFT) calculations indicate that the presence of Co NPs promotes the conversion of oxygen-containing intermediates for Co-Nx sites. The optimized catalysts display a half-wave potential of 0.9 V (vs RHE) for oxygen reduction reaction (ORR) and a low overpotential of 327mV at 10mAcm-2 for oxygen evolution reaction (OER) in alkaline media, which significantly outperforms the counterpart single structure, as well as noble-metal-based catalysts. Specifically, the PEMFCs and ZABs derived from CoNP/SA-NC/Fe-NCNTs catalyst exhibit power densities of 702 and 192mWcm-2, respectively. This work offers novel insights into the synthesis of the composited bifunctional carbon materials for ZABs and PEMFCs application.

Parameter Identification of PEMFC Model Using Improved Dung Beetle Optimization Algorithm

A proton exchange membrane fuel cell (PEMFC) is a complex system with multiple inputs and outputs, nonlinearity and strong coupling, and the establishment of an accurate model is the basis for evaluating the performance of PEMFC and developing control strategies. As the majority of the current intelligent algorithms tend to become stuck in local optimum when attempting to determine the PEMFC model’s parameters, resulting in low accuracy of parameter identification and poor model generalization ability, we propose an Improved Dung Beetle Optimization (IDBO) algorithm to identify the PEMFC model’s best parameters. To evaluate the IDBO algorithm’s performance, we identify the model optimal parameters of two typical commercial stacks, BCS 500 W and NedStack PS6, and the self-developed 3 kW PEMFC system, with the minimization of the sum of squared errors between the experimental output voltages and the model output voltages as the objective function. The verification results indicate that the IDBO algorithm has better convergence performance and higher parameter identification exactitude than the DBO algorithm. The robustness and applicability of the IDBO algorithm in addressing the issue of parameter identification of the PEMFC models are verified.

Impact of Transition Metals and Electrocatalyst Layer Thickness on the Pt‐Based Cathodes of Proton Exchange Membrane Fuel Cells – Do Multimetallic Electrocatalysts Necessarily Yield an Improved Performance?

AbstractThe interplay between i) cathodic electrocatalytic layer (EC layer) features of proton exchange membrane fuel cell (PEMFC), focusing on the oxygen reduction reaction (ORR) electrocatalyst (EC) and the Pt loading; and ii) the PEMFC performance and durability is evaluated. An innovative hierarchical “core–shell” carbon nitride multimetallic ORR electrocatalyst (“PtCuNi/C” H‐EC) is compared with a conventional Pt/C benchmark. The various contributions to PEMFC performance at beginning of test (BOT) are isolated and correlated to the physicochemical features of the ORR EC and the cathodic EC layer. The PEMFC durability is investigated extensively via accelerated stress tests (ASTs) mimicking long‐term operation. Particular attention is dedicated to determine how ageing affects: i) PEMFC cell voltage; and ii) the cathode electrochemically active surface area (ECSA). “Post‐mortem” studies are carried out to probe how ageing influences the cathodic EC layer features, including: i) chemical composition; ii) elements distribution; iii) EC morphology; and iv) structure and crystal size of the Pt‐based metal nanoparticles bearing the active sites. Integrating the experimental results allows to identify both the positive and the detrimental effects triggered by the introduction of transition metals (TMs) in the ORR EC on the factors modulating PEMFC performance and long‐term operation.

Tracking the Evolution of Ionomer Film and Catalyst Material to Unravel PEMFC Performance Degradation

Abstract Several characterization techniques were performed on a proton exchange membrane fuel cell (PEMFC) to relate the performance degradation induced by the membrane-targeted accelerated stress test (AST) to the evolution of electrochemical and physical properties of the electrode. This works investigated the ionomer structure and the proton transport properties. Electron microscopy and small angle neutron scattering analysis provided access to the electrode’s nanoscale structure, the distribution of the platinum particle size, the structure of the 2-3 nm thick ionomer film, as well as the location of the water uptake by the electrode. A newly-developed technique using proton desorption under diluted O2 allows to distinguish effectively used active sites for oxygen reduction reaction. Proton transport and dioxygen diffusivity properties were measured using impedance spectroscopy and limiting current technique respectively. The Membrane-AST leads to an increase in the water uptake of the electrode due to a modification of the global structure of the electrode, a reduced platinum surface area, and corrosion of carbon particles. However, it does not alter the ionomer structure. The decrease in performance is partially attributed to the increase in proton resistivity, but mainly due to the limitation of dioxygen transport fostered by the electrode structure modifications.

Impact of Gas Diffusion Layer Compression on Electrochemical Performance in Proton Exchange Membrane Fuel Cells: A Three-Dimensional Lattice Boltzmann Pore-Scale Analysis.

Proton exchange membrane fuel cells (PEMFCs) are being pursued for applications in the maritime industry to meet stringent ship emissions regulations. Further basic research is needed to improve the performance of PEMFCs in marine environments. Assembly stress compresses the gas diffusion layer (GDL) beneath the ribs, significantly altering its pore structure and internal transport properties. Accurate evaluation of the PEMFC cathode's electrochemical performance at the pore scale is critical. This study employs a three-dimensional multicomponent gas transport and electrochemical reaction lattice Boltzmann model to explore the complex interplay between GDL compression and factors such as overpotential, pressure differential, porosity, and porosity gradient on PEMFC performance. The findings indicate that compression accentuates the reduction in oxygen concentration along the flow path and diminishes the minimum current density. Furthermore, compression exacerbates the reduction in current density under varying pressure conditions. Increased local porosity near the catalyst layer (CL) enhances oxygen accessibility and water vapor exclusion, thereby elevating the mean current density. Sensitivity analysis reveals a hierarchy of impact on mean current density, ranked from most to least significant: overpotential, porosity, compression, porosity gradient, and pressure difference. These insights into the multicomponent gas transfer dynamics within compressed GDLs inform strategic structural design enhancements for optimized performance.

Modeling Analysis of the Impact of Platinum Oxides and Cerium Ion Migration on PEMFC Performance and Degradation Under a Realistic Driving Cycle

The sluggish oxygen reduction reaction (ORR) kinetics represents the major source of efficiency loss in a Proton Exchange Membrane Fuel Cell (PEMFC) [1]. In the potential range where fuel cells operate, several platinum (Pt) oxide species form on the catalyst surface [2]. Their formation and reduction is a dynamic process which strongly influences ORR activity and the loss of electrocatalyst active surface area (ECSA) [3]. PEMFC performance and durability are also significantly affected by Cerium (Ce) ions which, under typical operating conditions, are known to migrate through the polymer electrolyte membrane (PEM) and the catalyst layers (CLs) driven by concentration and potential gradients [4]. Such mobility reduces scavenging efficacy, thus accelerating PEM degradation. Moreover, it affects cell performance since the progressive build-up, during normal fuel cell operation, of Ce ions into the cathode CL is found to decrease proton conductivity [5] and hinder oxygen diffusion through the ionomer film [4], as highlighted by the most recent literature. In this scenario, a 1+1D multiphase dynamic non isothermal PEMFC model of performance is developed [6]: the close relationship between ORR reaction and Pt oxide dynamics is investigated by modeling oxides formation/reduction with a four-step oxidation mechanism which involves three different types of oxide species. Furthermore, based on the work of [2], the effects of ionomer sulfonate groups adsorption onto platinum surface and of local relative humidity are also included in the ORR kinetics. As visible in Figure 1(a), the proposed ORR formulation allows to properly capture cell voltage dynamics under the operating conditions of the automotive ID-FAST cycle [7]. The PEMFC model of performance also accounts for Ce ions mobility, both in the along-the-channel and through-the-membrane directions: for this purpose, a Nernst-Planck equation is adopted, where the diffusivity and migration coefficients are properly calibrated and validated (Figure 1(b)) by reproducing the Ce ions migration profiles reported in the literature for different current density [5].Lastly, the 1+1D multiphase dynamic non isothermal PEMFC model is coupled with a physical-based 0D model of platinum degradation [3]. The presented model framework is validated on experimental data gathered on a segmented hardware and representative of 600 cycles in the low power conditions of the automotive ID-FAST driving cycle load protocol [7]: as visible in Figure 1(c), the 67% of the initial ECSA is lost. Succeeding in the prediction, this modelling structure aspires to provide critical information for the development of proper mitigation strategies aimed at extending the lifetime of PEMFC stacks.This work received support from the Italian government Progetto PERMANENT - BANDO MITE PNRR Missione 2 Investimento 3.5 A - RSH2A_0O0012.[1] H.A. Gasteiger et al., Activity benchmarks and requirements for Pt, Pt-alloy, and non-Pt oxygen reduction catalysts for PEMFCs, Appl. Catal. B Environ. 56 (2005) 9–35. https://doi.org/10.1016/j.apcatb.2004.06.021.[2] A. Kongkanand et al., Platinum Surface Oxide and Oxygen Reduction Reaction Kinetics during Transient Fuel Cell Operation, J. Electrochem. Soc. 170 (2023) 094506. https://doi.org/10.1149/1945-7111/acfbbb.[3] E. Colombo, Understanding and mitigating degradation of PEMFC caused by real automotive operation, (2023). https://hdl.handle.net/2027.42/155288.[4] A.M. Baker et al., Cerium Ion Mobility and Diffusivity Rates in Perfluorosulfonic Acid Membranes Measured via Hydrogen Pump Operation, J. Electrochem. Soc. 164 (2017) F1272–F1278. https://doi.org/10.1149/2.1221712jes.[5] V.M. Ehlinger et al., Modeling proton-exchange-membrane fuel cell performance/degradation tradeoffs with chemical scavengers, JPhys Energy. 2 (2020). https://doi.org/10.1088/2515-7655/abb194.[6] F. Verducci et al., Dynamic Modeling of Polymer Electrolyte Membrane Fuel Cells Under Real-World Automotive Driving Cycle with Experimental Validation on Segmented Single Cell, Renew. Energy. (Currently under review).[7] E. Colombo et al., PEMFC performance decay during real-world automotive operation: Evincing degradation mechanisms and heterogeneity of ageing, J. Power Sources. 553 (2023) 232246. https://doi.org/10.1016/j.jpowsour.2022.232246. Figure 1

Comprehensive Evaluation of PEM Fuel Cells Recovery Exposed to Sulfur Dioxide in Air Stream

The future penetration of proton exchange membrane fuel cells (PEMFCs) in the market is limited by degradation and durability issues, lack of hydrogen refueling infrastructure and high overall cost of fuel cells compared to internal combustion engines [1]. The operation of PEMFCs using ambient air has demonstrated the negative impacts of common air impurities like SO2, NO2 and volatile organic compounds [2]. Performance drop originated from exposure to majority of the airborne contaminates can be self-recovered by operating the fuel cell with pure air. However, SO2 causes irreversible performance loss due to the electrochemical reduction of S-containing species and formation of elemental sulfur [3]. Only special treatments of the cathode lead to full or partial PEMFC recovery [4-6]. In this work a potential cycling as recovery procedure was comprehensively studied to assess its effectiveness and applicability to restore fuel cell performance exposed to SO2 under different conditions such as operating temperature and current using segmented cell approach.The experimental work was performed using a test station and a segmented cell system developed at Hawaii Natural Energy Institute [7]. Commercially available 100 cm2 catalyst coated membranes with Pt content of 0.1 and 0.4 mgPt cm-2 for both anode and cathode, respectively, were used in this work. The poisoning proceeded until the cell voltage reached a steady state, after that SO2 injection was stopped to assess the self-recovery in pure air following by the recovery procedure consisted of cyclic voltammetry (CV) from 0.1 to 1.2 V for 10 cycles at 20 mV/s.Fig. 1 shows the segment voltage and normalized individual segment current profiles under SO2 exposure and various operating conditions. The introduction of 5 ppm SO2 in the air stream led to a rapid drop in the segment voltage with an inflection point at ~0.62-0.63 V for 0.6 A cm-2 (Fig. 1 a) and 0.55-0.56 V at 1.0 A cm-2 (Fig. 1 c). At steady state conditions after several hours of SO2 contamination, the performance decreased by 280 mV at 60°C, while the cell voltage drop was 315 mV at 1.0 A cm-2 and 80°C (Figs. 1 a, c). At the same time, a redistribution of local current revealed similar patterns for the studied samples (Figs. 1 b, d).The operation of the MEAs in pure air immediately after cathode poisoning resulted in partial recovery of the performance and further local current distribution. The lack of full recovery is explained by the fact that only weakly bonded SOx species were removed from Pt, while formed S0 and strongly adsorbed S-containing species still covered the electrocatalyst surface [3, 5]. To recover the ECA, it is necessary to increase the cell potential to values where S0 can be oxidized. Therefore, to evaluate this approach, we applied the CV-induced recovery procedure.The CV-induced recovery of the MEA contaminated at 0.6 A cm-2 and 60°C led to cell potentials of 0.725 V vs. an initial performance of 0.735 V, which corresponded to 99% recovery and indicated full recovery (Figs. 1 a, b). At the same time, operation at higher temperature and lower cell potential (or higher operating current) resulted in pronounced differences between the initial and recovered performances, such as 105 mV for 1.0 A cm-2 and 80°C (84% of recovery) (Figs. 1 c, d) most likely due to of strongly bonded S0 and catalyst degradation. Thus, the PEMFC performance after exposure to SO2 at high temperature can be only partially recovered by the CV-induced approach and requires additional or modified recovery procedures.Detailed analysis of the local behavior of PEMFCs during the CV-induced recovery will be presented together with discussion of other potential recovery strategies.ACKNOWLEDGEMENTSWe gratefully acknowledge funding from ONR (N00014-22-1-2045). The authors thank K. Bethune and J. Huizingh for valuable support in operation.References L. Borup, A. Kusoglu, K.C. Neyerlin, et al, Curr. Opin. Electrochem. 210, 192-200 (2020).B. Shabani, M. Hafttananian, Sh. Khamani, et al, J. Power Sources, 427, 21-48 (2019).O. Baturina, B.D. Gould, A. Korovina, et al, Langmuir 27, 14930-14939 (2011).P. Jayaraj, P. Karthika, N. Rajalakshmi, K.S. Dhathathreyan, Int. J. Hydrogen Energy 39, 12045-12051 (2014).D. Gould, G. Bender, K. Bethune, et al, J. Electrochem. Soc. 157, B1569-B1577 (2010).K. Kakati, A. Unnikrishnan, N. Rajalakshmi, et al, Int. J. Hydrogen Energy 41, 5598-5604 (2016).T.V. Reshetenko, G. Bender, K. Bethune, R. Rocheleau, Electrochim. Acta 88, 571-579 (2013). Figure 1

Effect of GDL Structure and Operating Conditions on PEMFC Performance and Liquid Water Removal

Proton exchange membrane fuel cells (PEMFCs) are a highly efficient and environmentally friendly energy device that has potential for fuel cell vehicles and other applications due to its low operating temperature and compact size. The PEMFC is assembled by placing a membrane electrode assembly (MEA), which consists of a polymer electrolyte membrane with a catalyst layer and a gas diffusion layer on both sides, between separators.The GDL is responsible for diffusion of the reaction gas into the catalyst layers, current collection and removal of produced water. Excessive accumulation of produced liquid water within the GDL, known as flooding, inhibits reaction gas feed and causes concentration overpotential. Therefore, clarification of oxygen transport and produced water removal characteristics is essential to improve cell performance.The objective of this study is to clarify the effects of different GDL structures and operating conditions, such as cell composition, gas flow rate, and humidification conditions, on the liquid water production and removal characteristics and power generation. In this study, the cells with two types of GDLs were prepared and the liquid-water behavior in the MEA and the power generation performance during fuel cell operation under various conditions were investigated using X-ray radiography. Since the effect of GDL structure depends on the cell composition and operating conditions, the GDLs were characterized under the power generation tests of the cell.PEMFCs with a catalyst layer reaction area and a GDL area of 5×8 mm2 were constructed. Two types of GDL structures were used in the cathode. One was a conventional GDL (SIGRACET®GDL28BC, SGL) and the other was a novel GDL developed by Enomoto Co., Ltd [1-4]. On the other hand, the same GDL (28BC) was used in the anode. The PEMFC was observed with an X-ray imaging system consisting of an X-ray source (TX-9000D, Mars Tohken Solution) and a detector (C15926-01, Hamamatsu Photonics). Hydrogen and air were supplied to the anode and cathode, respectively. The relative humidity of the anode and cathode was 90%. In-situ observation of the liquid water behavior in the PEMFC was performed by taking images in the MEA cross-sectional direction simultaneously with power generation.Figure 1 shows an X-ray visualization image of liquid water after 800 seconds of power generation at a current density of 0.5 A/cm2 under highly humidified conditions. In this condition, excessive water was produced, causing some of the channels to become plugged with liquid water. The average liquid water thickness of the GDLs under the unblocked channel, indicated by the yellow frame in the figure, was 1.33 mm for the Enomoto GDL and 2.75 mm for the SGL GDL. The result suggests that the liquid water removal property under the operating condition is different depending on the types of GDLs.AcknowledgmentsThis work was partially supported by NEDO of Japan through the ECCEED_GDL project.

Impact of CeO2 Nanofiller on the Physicochemical Properties, Conductivity Mechanism and Tolerance to Radical-Induced Degradation of Hybrid Inorganic-Organic Proton-Exchange Membranes Based on an Aquivion™ Matrix

Proton exchange membrane fuel cells (PEMFCs) are electrochemical energy conversion devices that are playing a pivotal role in today’s energy transition away from fossil fuels [1]. The proton exchange membrane (PEM) at the heart of each PEMFC modulates key performance features such as the power density of the device. The PEM also contributes heavily to set the durability level of the entire PEMFC. State-of-the-art PEMs consist of perfluorinated ionomers functionalized with perfluoroethereal side chains terminated with highly acidic –SO3H groups. There are several different families of perfluorinated ionomers for implementation in PEMs, that are mainly distinguished on the basis of the chemical nature of the perfluoroethereal side chains and of their density along the backbone. A few examples of such ionomers include Nafion™, Aquivion™, Flemion™ and other macromolecules devised by 3M and Asashi. All these ionomers exhibit a high chemical, thermal and mechanical stability and a good proton conductivity at high hydration levels [2].One of the main mechanisms on the basis of the loss of performance in PEMFCs is the degradation of the PEM prompted by radicals. The latter are formed as byproducts of the electrode processes upon PEMFC operation [3]. The negative effect of radicals on PEMs can be mitigated by the introduction of dopants, that act as radical scavengers [4]. In this work, a new family of hybrid inorganic-organic PEMs is presented, consisting of an Aquivion™ matrix dispersing CeO2 nanopowders. The PEMs undergo an extensive physicochemical characterization to study their ion-exchange capacity (IEC), thermal properties, morphology and structure. The electrical response of the PEMs is examined in detail by means of broadband electrical spectroscopy (BES). The resulting information is integrated to elucidate the long-range charge migration mechanism. The PEMs are studied: (i) as a function of hydration; and (ii) both in the pristine state and upon treatment with Fenton’s reagent. This allows to obtain a comprehensive picture on how the introduction of the CeO2 nanofiller: (i) affects the mesoscale features of the Aquivion™ matrix; and (ii) mitigates the degradation phenomena triggered by the exposure of the PEM to radicals.

Engineering Anode Catalyst Supports for Enhancing Anode Reversal Tolerance in Proton Exchange Membrane Fuel Cells

The "hydrogen society" concept has emerged as a response to the increasing demand for carbon-free energy and the aim of achieving "carbon neutrality". Proton exchange membrane fuel cells (PEMFCs) are considered the most promising hydrogen energy utilization units for commercialization, despite facing challenges related to durability and cost. One of the key obstacles is anode reversal, which inevitably occurs during the operation of PEMFC and significantly reduces performance, eventually leading to failure. Therefore, it is essential to investigate the mechanisms that affect anti-reversal performance and find effective strategies to improve reversal tolerance without compromising performance.Two approaches have been put forward. First, we aim to enhance the reversal tolerance of proton exchange membrane fuel cells (PEMFCs) by using polyaniline (PANI) coated carbon as a catalyst support. The PANI coating acts as a protective layer that isolates the carbon from the corrosive environment, resulting in improved anti-reversal performance. Moreover, the PANI coating helps to distribute the catalyst nanoparticles and ionomer uniformly, leading to enhanced polarization. We have tested various carbon supports to confirm the applicability of this coating strategy and optimized the thickness of the PANI coating to avoid any adverse effects on performance. Additionally, we have developed a high-specific-surface-area conductive oxide Ti4O7 as an anode catalyst support to overcome the negative effects of carbon corrosion. By shortening the electron transfer pathway and increasing metal coverage, we have achieved comparable polarization performance to conventional carbon-supported counterparts. Our Ir@IrOx/Pt/Ti4O7-fabricated RTA has demonstrated approximately ten times longer reversal time (6 hours) and two orders of magnitude lower degradation rate than the conventional carbon-supported counterpart. These systematic studies aim to promote the development of highly durable and reversal-tolerant anodes, providing a promising outlook for practical, high-performance, low-degradation, and cost-effective RTA fabrication.

Acid Modified Carbon Support with Proton Conductive Properties for Polymer Electrolyte Membrane Fuel Cell Applications

Proton exchange membrane fuel cell (PEMFC) are one of highly efficient electrochemical energy conversion technologies, with a potential to replace conventional fossil-fueled power generators for vehicles and stationary applications. One of the challenges for widespread use of PEMFC is to minimize the amount of platinum (Pt) to lower the cost of PEFCs. Therefore, optimizing electrocatalyst design to improve Pt mass activity is required. In the conventional PEMFC electrocatalyst, the proton conductive polymers such as Nafion are contained to transport protons to the Pt surface. However, the main problem of Nafion in catalyst layer (CL) is the inhomogeneously covered on commercial catalyst of Vulcan/Pt (CB/Pt) surface leads a low proton conductivity or high O2 diffusion resistance. Furthermore, the SO3 − groups of the polymers are strongly adsorbed onto the Pt surface and decreasing Pt active sites to lower the catalytic activity. Hence, it’s necessary to develop a new CL without using ionomer (Nafion).An acid modified carbon support with proton conductive properties was considered for PEMFC applications. In our previous study, we synthesized a high-density -SO3H modified carbon support (named SCB) by covalent bonding and loaded Pt on SCB (SCB/Pt) to conductive proton. Attained a higher O2 diffusivity at high current density range because without Nafion added [1]. However, this method of destroying the sp2 structure of carbon has the problem of reducing the durability and electrical conductivity of carbon. In this work, we changed the acid modify carbon method from chemical modification to physical modification which using proton conductivity polymer adsorb on carbon surface to conductive proton. Polybenzimidazole (PBI) having a side chain of trifluorosulfonimide (PBI-TFSI) was chosen as a proton conductor adsorbed on carbon surface because PBI-TFSI was reported to have high proton conductivity [2].In this study, instead of adding Nafion as a proton conductor after loading Pt on carbon support, Pt is directly loaded on carbon support coated with PBI-TFSI to fabricate novel catalyst, CB/PBI-TFSI/Pt, and CL was fabricated. Absence of ionomer is expected to improve O2 diffusivity in the CL and also avoid specific adsorption of SO3 − groups on the Pt surface. Principal experiment of this study is synthesis composite, characterize the catalyst properties and evaluate of electrochemical cell performance. As the control catalyst, commercial CB/Pt (TKK10V30E) was used.The PBI-TFSI content of CB/PBI-TFSI was estimated by CHN elemental analysis, which revealed that its C: H: N atomic ratio was 0.37: 95.59: 0.61. Considering that all the nitrogen was originating from PBI-TFSI, and side chain of graft ratio is 73.25%, the PBI-TFSI content of CB/PBI-TFSI was determined to be 4.5%. Thermal stability of the catalysts was compared by thermogravimetric analysis (TGA). As the results, CB/PBI-TFSI displayed a one-step weight loss similar to that of CB with a degradation temperature around 650°C, while SCB started to drop at 550°C [1]. This superior thermal stability of CB/PBI-TFSI compared to SCB was because sp3 defect was not introduced by using polymer wrapping method, while chemical modification method used to SCB introduced sp3 defects. Such a good thermal stability is expected to offer the high electrochemical durability in the PEMFC operation. The Pt loading of CB/PBI-TFSI/Pt determined from the TGA weight residue at 900 °C was 30 wt% comparable with CB/Pt. The size of the Pt nanoparticles in both CB/PBI-TFSI/Pt and CB/Pt was analyzed by TEM. The determined sizes of the Pt nanoparticles in CB/PBI-TFSI/Pt and CB/Pt were 2.04 ± 0.3 and 2.10 ± 0.2 nm, respectively. The comparable Pt loading and size of Pt nanoparticles in CB/Pt and CB/PBI-TFSI/Pt mean that these samples can be used in comparative studies.For the electrochemical characterization, the electrochemical active surface area (ECSA) was determined using the hydrogen adsorption/desorption (HAD) method and the polarization curves are operated using H2/air. The results indicated that the cell of CB/PBI-TFSI/Pt exhibits activity over 1.0 A/cm2 current density even without ionomer. However, compare with commercial catalyst of CB/Pt with Nafion, CB/PBI-TFSI/Pt still shows a lower cell performance because the higher resistance between Nafion membrane and CL. Additional improvements to the proton conductivity of the acid-grafted carbon support and the reduction of the interfacial resistance between PEM and CL could potentially further increase the PEMFC performance. O2 diffusivity as well as the fuel cell operation under the low humidity will also discuss.[1] Yoshihara R, Wu D, Phua YK, Nagashima A, Choi E, Jayawickrama SM, et al. Journal of Power Sources. 2022;529:231192.[2] Han H, Miura H, Motoishi Y, Tanaka N, Fujigaya T. Polymer Journal. 2021;53:1403-11. Figure 1

Investigation of PEMFC Cathode Rf-Dependent Performance Losses for Voltage Cycling and Start-up Accelerated Stress Tests

In order to replace internal combustion engines in the heavy-duty (HD) transportation sector, proton exchange membrane fuel cells (PEMFCs) require extended operating hours with minimal performance loss.[1] During research and development, the fuel cell stack performance loss for >30,000 hours of operation can be estimated by tailored accelerated stress tests (ASTs) that induce typical degradation modes which can be tested in small active area single-cells. Two of the main cathode catalyst layer degradation modes resulting in a reduced electrochemical surface area are Pt degradation by load/voltage cycling (VC) and carbon support degradation by start-up (SU).VC ASTs induce performance losses by decreasing the roughness factor (rf) of the cathode catalyst, due to Pt particle growth through the mechanism of Ostwald ripening and by loss of the Pt into the ionomer/membrane phase.[2] For small cathode rfs, an increase in O2 transport resistance leads to a severe drop in performance. As shown in previous studies, during VC ASTs a characteristic correlation between cathode rf and H2/air performance loss can be found for a given membrane electrode assembly (MEA).[3] However, performance losses during SU ASTs originate from a combination of Pt degradation and carbon corrosion,[4,5] which is affecting this characteristic correlation.This study will focus on HD relevant VC and SU protocols to mimic cathode catalyst layer degradation during PEMFC operation. For the SU AST, an adapted protocol from Bisello et al. [5] is applied to an MEA with a Pt/C cathode catalyst in a 50cm2 single-cell setup. The rf-dependence of the H2/Air performance is reevaluated for the SU protocol, comparing it to the VC AST. Furthermore, VC and SU protocols are combined to get further insights into the design of combined AST protocols and the resulting lifetime assessment of cathode catalyst layers undergoing mixed modes of degradation.

Performance evaluation and field synergy analysis of PEMFC with novel snake coil flow field

In the development process of proton exchange membrane fuel cells (PEMFC), the design of the flow field structure plays an important role in improving its mass transfer and performance. In this survey, a novel serpentine channel flow field (SCFF) construction is initially proposed, a 3D multiphase mathematical model is developed, and the accuracy of the mathematical model is confirmed by means of experimental data. Secondly, based on the fluid simulation software, the performance difference between SCFF with different numbers of turns and conventional flow fields (single serpentine and parallel flow fields) in terms of electrochemical reaction and reactant transportation is comparatively analyzed. Finally, the effect on PEMFC performance of the mass transport capability with the novel flow field is evaluated by the theory of mass-transfer loss rate and field synergy. The studies indicate that as the number of turns grows, the output performance of the proposed flow field progressively enhances. The net power density of the flow channel structure with five turns (SC-5) is increased by 35.3% compared with that of the flow channel structure with two turns (SC-2), and the SC-5 flow field also has higher output performance compared with the two conventional flow fields, with an increase of 7.2% and 27.9% in net power, respectively. Meanwhile, the synergistic efficacy between velocity vector field and concentration field is gradually enhanced with the increase in the number of turns, and the results show that SC-5 has the most optimal mass-transfer capability.

Expanding the Scope of ZIF-Derived Carbons Towards Tailored Architectures and Compositions

Proton exchange membrane fuel cells (PEMFCs) represent a promising technology for clean energy conversion. The key chemical transformation within a fuel cell is conducted by catalyst nanoparticles tethered to a carbon support. Although the carbon support plays a critical role in maximizing the performance and durability of the catalyst nanoparticles and mass transport, predictably tuning the chemical environment and pore architecture of the carbon support remains a challenge. Metal–organic frameworks are a class of crystalline porous coordination polymers known for their structural and chemical tunability. Recently, metal–organic frameworks (MOFs), almost exclusively zeolitic imidazolate framework-8 (ZIF-8), have been used as precursors to generate carbon supports where the MOF architecture serves as a template to generate the carbon skeleton. As a result, these materials have an improved homogeneous porous landscape and, encouragingly, superior PEMFCs performance and durability. Herein, we leverage the vast library of MOFs and report design principles for generating precisely tuned carbon support architectures through systematic changes to the structure and chemical composition of MOFs. Advanced fuel cell testing of PEMFCs featuring these novel carbon architectures offers fine level insight into the effects of pore size, connectivity and chemistry on the performance of PEMFCs.Acknowledgement: This research was supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, US Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortium, technology managers G. Kleen and D. Papageorgopoulos.

Evaluating the Measurement Uncertainty of Single Cell PEMFC Performance

A single cell proton exchange membrane fuel cell (PEMFC) is commonly used as a screening test to assess the impact of materials and operating conditions on these devices, with its performance commonly stated in terms of cell voltage at a given current density. Although standardised testing protocols exist and have been widely adopted, a universal method of assessing the uncertainty on the results has yet to be established. This complicates the task of comparing results/measurements made in different labs and evaluating the reliability of the conclusions. In this work, we estimated the uncertainty on PEMFC performance running at static standard operating conditions. Using results across three identical repeats and a sensitivity analysis of the various controllable input parameters to the fuel cell, we arrived at an expanded measurement uncertainty (k=2) for cell voltage of 32 mV at 1 A cm-2. The largest contributors to the measurement uncertainty were clearly air flow rate (stoichiometry) and cathode pressure. Figure 1

Numerical Analysis of Patterned Gas Diffusion Layers with Hydrophilic Surface in Proton Exchange Membrane Fuel Cell

Proton exchange membrane fuel cells (PEMFCs) are electrochemical energy conversion devices which have strengths in efficiency and versatility. Water management is a major research topic for PEMFCs due to their low operating temperatures below 100 ℃ . The gas diffusion layers (GDL) play an important role in the water management of PEMFCs. The GDL typically get hydrophobic treatments to remove liquid water and facilitate high performance of PEMFCs. However, Islam et al. experimentally presented that hybrid wettability of GDL can promote liquid water transport by providing pathway for uninterrupted mass transfer. In this study, the effects of hydrophilic surface on patterned GDL were investigated via three-dimensional multiphase simulation. Vertical and horizontal stripe patterned GDL on serpentine flow field were applied to the cathode side. The performance with and without the hydrophilic surface on each patterned GDL were compared. The mass transfer characteristics of each case, especially convection, were analyzed.

Novel reinforcement learning technique based parameter estimation for proton exchange membrane fuel cell model

Proton Exchange Membrane Fuel Cells (PEMFCs) offer a clean and sustainable alternative to traditional engines. PEMFCs play a vital role in progressing hydrogen-based energy solutions. Accurate modeling of PEMFC performance is essential for enhancing their efficiency. This paper introduces a novel reinforcement learning (RL) approach for estimating PEMFC parameters, addressing the challenges of the complex and nonlinear dynamics of the PEMFCs. The proposed RL method minimizes the sum of squared errors between measured and simulated voltages and provides an adaptive and self-improving RL-based Estimation that learns continuously from system feedback. The RL-based approach demonstrates superior accuracy and performance compared with traditional metaheuristic techniques. It has been validated through theoretical and experimental comparisons and tested on commercial PEMFCs, including the Temasek 1 kW, the 6 kW Nedstack PS6, and the Horizon H-12 12 W. The dataset used in this study comes from experimental data. This research contributes to the precise modeling of PEMFCs, improving their efficiency, and developing wider adoption of PEMFCs in sustainable energy solutions.

Dynamic thermal and mass transport in PEM fuel cells at elevated temperatures and pressures: A 3D model study

Next-generation proton-exchange membrane fuel cells (PEMFCs) encounter significant challenges at elevated temperatures (OTs) and pressures (OPs) due to local thermal and mass fluctuations. In this study, a three-dimensional transient model was developed to analyze these dynamics by incorporating the effects of the microporous layer and variations in the coolant temperature along the channel. The results indicate that increasing the OT from 80 °C to 90 °C decreases the output voltage by 34–78 mV, increases voltage undershoot/overshoot by 0.2–16.6 mV, and raises the temperature difference between the cathode catalyst layer (cCL) and coolant from 1.2 to 2.1 °C, leading to more irregular temperature fluctuations in the cCL. These effects stem from the increased gas–liquid water outflow within the cCL that induces membrane dehydration, particularly in the electrolyte near the channel. Consequently, the lag in proton conduction relative to the oxygen reduction reaction (ORR), as quantified by the newly introduced Damköhler number, has emerged as a critical factor that influences both heat transfer and reaction kinetics. Conversely, increasing OPs from 130 kPa [anode]/120 kPa [cathode] to 400 kPa [anode]/390 kPa [cathode] improves output voltage by 50–150 mV and reduces proton conduction hysteresis by 12–54 % under dynamic loads. This improvement is linked to higher O2 concentration and membrane water facilitated by a 0.6–2 °C decrease in cCL temperature. However, the rise in OPs also results in an increased voltage undershoot/overshoot due to greater fluctuations in the membrane water content, ultimately leading to additional power loss. These findings are crucial for optimizing PEMFC performance under extreme conditions and advancing fuel cell technology.

Numerical investigation of PEMFC performance enhancement through combined design of anodic fishbone ridge groove channel and optimal gas diffusion layer porosity gradient

The flow field plate is one of the core components of proton exchange membrane fuel cells (PEMFC), and its structure significantly influences the thermo-electrochemical coupling transport characteristics of PEMFCs. Optimizing the parameters of the flow channels of bipolar plates is crucial for enhancing the mass transfer of reacting gas and improving water removal capacity. In this study, an anodal fishbone ridge groove combined flow channel (F-SFC) is designed to enhance the diffusion uniformity of anode hydrogen gas, and a 3D multi-phase model of PEMFC is established using the multiphysics simulation software COMSOL Multiphysics. The F-SFC was compared with traditional bipolar plates featuring symmetric anode and cathode flow channels in terms of overall output performance, and the results are presented. The findings indicate that the F-SFC design achieves an average increase of 28.78% in current density and 21.07% in power density compared to conventional fishbone flow channels. When compared to traditional serpentine flow channels, the F-SFC design shows a 13.5% increase in current density and a 10.42% increase in power density. Furthermore, adding multilayer porosity gradients to gas diffusion layers (GDLs) greatly improves internal mass transfer. A gradient porosity of 0.7, 0.5, and 0.3 along the Z-axis produces a more equal distribution of current density and water concentration on the membrane. This work sheds fresh light on optimizing PEMFC design for increased power density, providing useful theoretical advice for future advances.