High Temperature Proton Exchange Membrane Fuel Cell Performance Research Articles

Operando synchrotron-based X-ray study and intervention approaches of graphene-related-materials for investigating the performance and durability of HT-PEMFC

The application of high-temperature proton exchange membrane fuel cells (HT-PEMFCs) addresses challenges in water management, fuel purity, and overheating under high current density. However, phosphoric acid (PA) migration hinders their development. This study uses synchrotron-based X-ray fluorescence spectroscopy to investigate PA and catalyst migration. Interventions with single-layer graphene and electrochemically exfoliated graphene oxide improve performance and durability. X-ray absorption spectroscopy provides insights into relevant mechanisms, advancing understanding of membrane electrode assembly preparation and the intricate influences of PA and catalyst migration on performance and durability in HT-PEMFCs.

Silane-crosslinked polybenzimidazole with different hydroxyl content for high-temperature proton exchange membrane

High temperature proton exchange membrane fuel cells (HT-PEMFCs) can operate over 100 °C without humidification, which avoids the catalyst poisoning and enhances the efficiency of the power conversion. However, the classic phosphoric acid (PA) doped polybenzimidazole (PBI) still remains the challenge in the trade-off between mechanical strength and proton conductivity. The γ-(2,3-epoxypropoxy) propyltrimethoxysilane (KH560), as a crosslinking agent, is widely used to improve the mechanical properties of membranes. Although it can enhance the mechanical strength of PBI membranes, it sacrifices the hydrogen of imidazole groups, resulting in a decrease in proton conductivity. In this present work, silane-crosslinked PBI proton exchange membranes (PEMs) were synthesized by the reaction between the pyridine-bridged PBI containing different hydroxyl (-OH) content with KH560. Through comprehensive structural characterization of the polymer and model compound, it has been determined that this crosslinking method does not compromise the N–H acidic sites on the imidazole ring. The crosslinking agent KH560 provides additional hydroxyl groups to PBI and participates in the construction of hydrogen bonding networks after the ring-opening reaction. It was found that the addition of pyridine and hydroxyl groups could promote the phosphoric acid uptake, and the appropriate degree of silane crosslinking could maintain the PBI membranes with reasonable mechanical properties. Proton conductivity and HT-PEMFCs performance of the obtained crosslinked films were further enhanced with the dimensional stability, thermal stability and mechanical properties. Among them, CPyOPBI–OH–20 presented the best overall performance, exhibiting the highest proton conductivity of 0.095 S cm−1 and the maximum power density of 767 mW cm−2 at 180 °C under the anhydrous condition, which was 4.2 times that of OPBI (182 mW cm−2).

Coupling of high-temperature proton exchange membrane fuel cells with methanol steam reforming: Modeling and simulation for an integrated coupled for power generation system

This study established a zero-dimensional numerical model integrating methanol steam reforming (MSR) and high-temperature proton exchange membrane fuel cells (HT-PEMFC), systematically investigating the effects of parameters such as steam-methanol (S/C) ratio, reformer reaction temperature, methanol catalytic combustion ratio, fuel cell number, and anode stoichiometry on the thermal, mass, electrical, and efficiency performance parameters of the integrated system. The results confirmed that the integrated system can achieve thermal self-sustained operation without the need for additional heat from methanol catalytic combustion. Improved insulation quality enables the attainment of thermal self-sufficiency at lower operating conditions. The molar ratio of CO in the reformate increases with a decrease in the S/C ratio and an increase in the reformer reaction temperature. The system achieves maximum output power and efficiency when S/C equals 1.25 and the reformer temperature is 513 K, with increases of 8.6 % and 37.1 %, respectively. The system efficiency is highly sensitive to the anode stoichiometry of the fuel cell, showing an 11.7 % improvement as the stoichiometry decreases from 2.0 to 1.2. Based on these results, three improvement measures were proposed to enhance the performance of MSR and HT-PEMFC integrated systems: improving system insulation to lower thermal self-sufficiency conditions, optimizing the stoichiometry of the bipolar plates for significant efficiency improvement, and selecting appropriate operating parameters for system components to enhance overall performance. This study quantitatively demonstrates the potential of these measures to improve system performance, providing valuable insights for the design and optimization of integrated systems.

Balancing proton and mass transfers in cathode catalyst layer of high-temperature proton exchange membrane fuel cell via gradient porous structure design

The porous structure within the cathode catalyst layers (CLs) plays a crucial role in facilitating phosphoric acid (PA) invasion and oxygen diffusion, which was essential for establishing the triple-phase boundaries (TPBs) in high-temperature proton exchange membrane fuel cells (HT-PEMFCs).In this work, a gradient porous structure is deliberately constructed within the cathode CL by carefully controlling the microstructures of the double CLs. The effects of pore diameter distribution in the cathode CL and PA content in the membrane electrode assembly (MEA) on the single cell performance of HT-PEMFC are systematically investigated. By incorporating an appropriate amount of PA in the MEA, along with the optimized gradient porous structure, the inner pores effectively stored acid and prevented its outward diffusion. Simultaneously, the pores in the outer CL provided additional pathways for oxygen transfer. Consequently, the optimized gradient porous structure enhanced the peak power density of H2/Air fuel cells to 0.510 W cm−2 at a Pt loading of 0.5 mgPt cm−2, a notable improvement compared to 0.396 W cm−2 of the traditional single CL. The mechanism analysis further reveals that the cathode CL with gradient porous structure can successfully balance proton transfer and mass transfer, hence reducing the polarizations in fuel cell.

Multi-Objective Assessment and Optimization of a High-Temperature Proton Exchange Membrane Fuel Cell: Steady-State Analysis

The design and operational conditions of high-temperature proton exchange membrane fuel cells (HT-PEMFCs) substantially impact their performance. This model aims to investigate the influence of various parameters on the performance of HT-PEMFC. A comprehensive examination revealed that the performance of HT-PEMFC experienced a significant enhancement through modifications to the operating temperature, doping levels, and membrane thickness. Significantly, it can be observed that operating pressure showed a limited influence on performance. The HT-PEMFC was optimized using the non-dominated sorting genetic algorithm II (NSGA-II), specifically emphasizing three primary performance indicators: equivalent power density, energy efficiency, and exergy efficiency. The findings demonstrate promising outcomes, as they reveal a noteworthy enhancement in power density by 17.72% and improvements in energy efficiency and exergy efficiency by 21.11% and 10.37%, respectively, compared to the baseline case.

Sensitivity Analysis of Operational Parameters of a High Temperature-Proton Exchange Membrane Fuel Cell

The lack of widespread commercialization of High-Temperature Proton Exchange Membrane Fuel Cells (HT-PEMFC) is primarily due to their poor performance and durability. Various factors impact the performance of fuel cells, one such crucial factor being the operational parameters. Suitable operating conditions not only enhance the output cell performance but also extend a fuel cell’s life. Current research on the impact of operational factors on HT-PEMFC performance is largely qualitative in nature, with no quantitative indication of affecting the sensitivity of these parameters. In the present work, a three-dimensional, non-isothermal HT-PEMFC model developed earlier is used to investigate the influential sensitivities of five crucial operating parameters, each with four different levels, and is analyzed quantitatively using six evaluation indexes. The orthogonal/Taguchi method L16(45) is implemented to investigate the impact of operating parameters quantitatively. Further, the effect of each operating parameter on evaluation indexes under different operational current density regimes is investigated. The findings show that, of the parameters chosen, the working temperature and cathode pressure are the most sensitive to cell voltage and cathode overpotential distribution under all operating current density regimes. The findings would provide more precise recommendations for experimental research targeted at improving cell performance by optimizing operational parameters.

Analysis of dead-end anode operation phenomena based on a novel transient 3D model of high-temperature proton exchange membrane fuel cell

The dead-end anode (DEA) mode effectively improves hydrogen utilization rate of high-temperature proton exchange membrane fuel cell (HT-PEMFC). However, being in DEA mode for a long time can lead to hydrogen starvation in HT-PEMFC and reduce its performance. This study aims to reduce the adverse effects of DEA on HT-PEMFC by setting up appropriate operating conditions. A novel transient model of HT-PEMFC was successfully developed by considering gas crossover phenomena. The paper evaluates the effects of key operating parameters, geometric parameters, and gas crossover phenomena on the transient performance of HT-PEMFC in DEA mode. The results show that the performance deterioration over time during the DEA process varies under different operating conditions. The amount of hydrogen and oxygen crossover decrease significantly with the increase of membrane thickness. In DEA mode, the performance of HT-PEMFC decreases with increasing of water vapor transport coefficient; when the anode is open, the comprehensive performance of medium water vapor transport coefficient is the best. This work can provide a suitable working condition scheme to reduce the adverse effects of DEA on HT-PEMFC.

Numerical study on performance of HT-PEMFC with gradient design of Pt loading

In this paper, the spatial distribution of overpotential and current density of high temperature proton exchange membrane fuel cell (HT-PEMFC) with gradient design of platinum (Pt) loading is studied. Three Pt loading gradient distributions are considered: along the thickness direction of the catalyst layer (CL), along the flow direction and the bidirectional linear gradient distribution. The results show that the increase of the Pt loading near the membrane could improve the fuel cell performance and catalyst utilization when the total amount of Pt in CL consistent. In addition, the increase of Pt loading along the flow direction provides a more uniform current density for the fuel cell, but lower cell performance. The bidirectional linear gradient distribution of Pt loading is studied, and the results show that the current density distribution is more uniform, but the cell performance is slightly improved. Therefore, the results demonstrate that the reasonable distribution of Pt loading can improve the cell performance and improve the uniformity of current density, which is of great significance to improve the utilization of catalyst.

Analyses of the Effects of Electrolyte and Electrode Thickness on High Temperature Proton Exchange Membrane Fuel Cell (H-TPEMFC) Quality.

Researchers have been striving to minimize proton exchange membrane fuel cell components thickness. This is believed to reduce the losses (active losses, ohmic losses and mass transfer losses) associated with this cell. In this study, we numerically analyze the electrodes and electrolyte thickness effects on high-temperature proton exchange membrane fuel cell (H-TPEMFC) performance. COMSOL Multiphysics is adopted to model both the impedance spectroscopy and polarization of the cell. Increased cell catalyst layer (thick electrode) improves the overall cell performance by ±10%, because of the improved reaction rate. It presents 0.89 mol m-3 lesser oxygen compared to that of the thin electrode cell. On the contrary, thick cell electrodes come with increased mass transport loss. The high reaction rate is also confirmed by the high amount of generated water, which is 0.42 mol m-3 higher than that of thin electrode cell. The experiment used to set the modeling parameter renders results with only less than 5% discrepancy to the modeling results. Also revealed is that over a limited range, electrolytes thickness variation has negligible effects on H-TPEMFC performance.

The influence of intrinsically proton conductive electrode binder materials on HT-PEMFC performance

High temperature proton exchange membrane fuel cells (HT-PEMFCs) typically employ either acid-absorbing or hydrophobic electrode binders in their catalyst layers (CLs). A recently introduced alternative is the ionomeric binder PWN, poly(2,3,5,6-tetrafluorostyrene-4-phosphonic acid). In literature, PWN with a phosphonation degree of 70% was shown to remarkably improve HT-PEMFC performance. Here, we investigate the influence of the phosphonation degree (40–95%) of this ionomeric binder on HT-PEMFC performance. PWN is employed in the cathode CL and compared to the commonly used polytetrafluoroethylene (PTFE) binder. The electrochemical behavior is tested at 180 °C at ambient pressure under H2/air conditions using a commercial phosphoric acid (PA)-doped PBI-membrane. HT-PEMFCs with PWN generally outperform fuel cells (FCs) with PTFE after a full break-in regarding peak power density (PPD), activation overpotential (as studied by Tafel analysis), and reproducibility in the mass transport region. Further, PWN-electrodes show higher electrochemically active surface areas (ECSAs) than PTFE-electrodes after completing the break-in. We find that the phosphonation degree has a substantial impact on the PPD, with PWNs with lower phosphonation degrees (40–60%) outperforming highly phosphonated PWNs (70–95%). Taken together, PWN as an ionomeric electrode binder in HT-PEMFCs shows remarkable improvements in performance, but a precise adjustment of the phosphonation degree is required to obtain optimal results.

Optimization of the thickness of catalytic layer for HT-PEMFCs based on genetic algorithm

In the design of High-temperature proton exchange membrane fuel cells (HT-PEMFC), the thickness of the catalyst layer (CL) determines to some extent the strength of the electrochemical performance of the cell and its manufacturing cost. To achieve the goal of improving the cell performance and reducing the manufacturing cost, the genetic algorithm was employed to optimize the thickness of the cathode and anode catalytic layers. The thicknesses of the anode/cathode CLs were set as independent variables. The results showed that the best minimum adaptation value was determined as 0.03072. The thicknesses of the anode and cathode CLs are 0.0231 mm and 0.0315 mm, respectively. The performance improvement of the optimized model is approximately 6.8%. The optimization method used in the study can effectively improve the performance of HT-PEMFC and provide a reference for the design of HT-PEMFC.

Performance Analysis of a HT-PEMFC System with 6FPBI Membranes Doped with Cross-Linkable Polymeric Ionic Liquid.

In this paper, a high-temperature proton-exchange membrane fuel cell (HT-PEMFC) system using fluorine-containing polybenzimidazole (6FPBI) composite membranes doped with cross-linkable polymer ionic liquid (cPIL) is developed and studied. The reliability of the model is verified by a comparison with the experimental data. The performance of the HT-PEMFC system using 6FPBI membranes with different levels of cPIL is analyzed. The results show that when the HT-PEMFC uses 6FPBI membranes with a cPIL content of 20 wt % (6FPBI-cPIL 20 membranes), the single cell power density is 4952.3 . The excessive cPIL content will lead to HT-PEMFC performance degradation. The HT-PEMFC system using the 6FPBI-cPIL 20 membranes shows a higher performance, even at higher temperatures and pressures, than the systems using 6FPBI membranes. In addition, the parametric study results suggest that the HT-PEMFC system should be operated at a higher inlet temperature and hydrogen pressure to increase system output power and efficiency. The oxygen inlet pressure should be reduced to decrease the power consumption of the ancillary equipment and improve system efficiency. The proposed model can provide a prediction for the performance of HT-PEMFC systems with the application of phosphoric-acid-doped polybenzimidazole (PA-PBI) membranes.

Finite Time Thermodynamic Modeling and Performance Analysis of High-Temperature Proton Exchange Membrane Fuel Cells.

In order to improve the output performance of high-temperature proton exchange membrane fuel cells (HT-PEMFC), a finite time thermodynamic (FTT) model for HT-PEMFC was established. Several finite time thermodynamic indexes including power density, thermodynamic efficiency, exergy efficiency, exergetic performance efficient (EPC), entropy production rate and ecological coefficient of performance (ECOP) were derived. The energetic performance, exergetic performance and ecological performance of the HT-PEMFC were analyzed under different parameters. Results showed that operating temperature, doping level and thickness of membrane had a significant effect on the performance of HT-PEMFC and the power density increased by 58%, 31.1% and 44.9%, respectively. When the doping level reached 8, the output performance of HT-PEMFC wa optimal. The operating pressure and relative humidity had little influence on the HT-PEMFC and the power density increased by 8.7%% and 17.6%, respectively.

Performance and Durability of HT-PEMFC Enhanced By One-Step Electrochemical Exfoliated Phosphonated Graphene Oxide

The high-temperature proton exchange membrane fuel cell (HT-PEMFC) conducts protons through the hydrogen bond network established by the polymer and phosphoric acid (PA), which reduces the dependence on humidity and allows its operating temperature to be higher than 100°C [1]. A higher operating temperature is conducive to improve catalyst activity, reducing carbon dioxide adsorption on the catalyst thus reducing the requirement for hydrogen purity, and convenient water management [2]. As the most widely commercialized HT-PEMFC proton exchange membrane material, the performance and durability of Polybenzimidazole (PBI) still need to be improved. In particular, it has insufficient proton conductivity, insufficient mechanical properties, and phosphoric acid leaching issues under high acid doping level [3] [4] [5].The doping of functionalized graphene oxide in the PBI membrane can build additional proton transfer channels, promote proton hopping and act as a trap for PA to reduce its leaching by virtue of abundant functional groups of functionalized GO [6] [7] [8]. Among the groups that can be used for functionalization, the phosphoric acid group has become one of the most promising due to its strong hydrogen bonding and water retention ability [9] [10] [11]. Phosphonated graphene oxide (PGO) is usually synthesized by further phosphonation of GO obtained by chemical exfoliation [6] [7]. Chemical exfoliation methods usually require the long-term action of strong acids and strong oxidants [12]. The safety and environmental issues caused by those methods can not be underestimated. And the two-step synthesis method of PGO has a long reaction period.This work achieved the rapid, safe, and large-yield production of electrochemically exfoliated PGO by using a 3D printed reactor, ammonium dihydrogen phosphate as the electrolyte and natural graphite flakes as the raw material. The two-step electrochemical exfoliation method of producing GIC with concentrated sulfuric acid as the first electrolyte is also used to synthesize electrochemical exfoliated (E)GO. 1.5wt% EGO or PGO was doped in the PBI membrane to explore the effect of different GO on the performance and durability of the PBI- membrane-based HT-PEMFC. Compared with pure PBI, the doping of EGO and PGO increases the peak power density of HT-PEMFC by 17.4% and 35.4%, respectively.[1] Y.-L. Ma, J.S. Wainright, M.H. Litt, R.F. Savinell, Journal of The Electrochemical Society 2004, 151, A8.[2] H. Su, S. Pasupathi, B. Bladergroen, V. Linkov, B.G. Pollet, International Journal of Hydrogen Energy 2013, 38, 11370.[3] S. Galbiati, A. Baricci, A. Casalegno, R. Marchesi, International Journal of Hydrogen Energy 2013, 38, 6469.[4] S.H. Eberhardt, F. Marone, M. Stampanoni, F.N. Büchi, T.J. Schmidt, Journal of Synchrotron Radiation 2014, 21, 1319.[5] Q. He, X. Yang, W. Chen, S. Mukerjee, B. Koel, S. Chen, Physical Chemistry Chemical Physics 2010, 12, 12544.[6] J. Yang, C. Liu, L. Gao, J. Wang, Y. Xu, R. He, RSC Advances 2015, 5, 101049.[7] C. Xu, Y. Cao, R. Kumar, X. Wu, X. Wang, K. Scott, Journal of Materials Chemistry 2011, 21, 11359.[8] Y. Cai, Z. Yue, S.X.-J. of A.P. Science, undefined 2017, Wiley Online Library 2017, 134, 44986.[9] E. Abouzari-Lotf, H. Ghassemi, A. Shockravi, T. Zawodzinski, D. Schiraldi, Polymer 2011, 52, 4709.[10] E. Abouzari-Lotf, M. Zakeri, M.M. Nasef, M. Miyake, P. Mozarmnia, N.A. Bazilah, N.F. Emelin, A. Ahmad, Journal of Power Sources 2019, 412, 238.[11] S. Some, I. Shackery, S.J. Kim, S.C. Jun, Chemistry - A European Journal 2015, 21, 15480.[12] C. Xu, Y. Cao, R. Kumar, X. Wu, X. Wang, K. Scott, Journal of Materials Chemistry 2011, 21, 11359.

Implementation of different Fe–N–C catalysts in high temperature proton exchange membrane fuel cells – Effect of catalyst and catalyst layer on performance

Fe–N–Cs are an alternative to Pt/C catalysts as they show promising activity towards the oxygen reduction reaction. While several studies are based on thin-film analysis in diluted electrolytes, only few reports show the application of Fe–N–Cs in gas diffusion electrodes (GDE) and their tests under high temperature proton exchange membrane fuel cell (HT-PEMFC) conditions. Here, a series of Fe–N–Cs with different physical properties are analyzed. GDEs are fabricated using ultrasonic spray and doctor blade coating to investigate the effect of coating method on the morphology and performance. Morphological analysis identified thinner catalyst layers for spray coating and inhomogeneous PTFE distribution for doctor blade coated GDEs. Electrochemical characterization in the HT-PEM half-cell displays significantly lower performance for ultrasonic spray-coated GDEs, possibly due to more pronounced phosphoric acid penetration. On the contrary, implementation of GDEs as cathodes in the HT-PEMFC yields comparable performances for both coating methods but differences in ORR and proton transport resistances determined by distribution of relaxation times analysis. Moreover, it was shown that inhomogeneous PTFE distribution caused by high amounts of hydrophilic O-/N-functionalities negatively affects HT-PEMFC performance. This study helps to understand the impact of GDE fabrication and Fe–N–C catalyst properties in HT-PEM half- and single-cell application.

Composite membrane by incorporating sulfonated graphene oxide in polybenzimidazole for high temperature proton exchange membrane fuel cells

The objective of this work is to examine the polybenzimidazole (PBI)/sulfonated graphene oxide (sGO) membranes as alternative materials for high-temperature proton exchange membrane fuel cell (HT-PEMFC). PBI/sGO composite membranes were characterized by TGA, FTIR, SEM analysis, acid doping&acid leaching tests, mechanical analysis, and proton conductivity measurements. The proton conductivity of composite membranes was considerably enhanced by the existence of sGO filler. The enhancement of these properties is related to the increased content of –SO 3 H groups in the PBI/sGO composite membrane, increasing the channel availability required for the proton transport. The PBI/sGO membranes were tested in a single HT-PEMFC to evaluate high-temperature fuel cell performance. Amongst the PBI/sGO composite membranes, the membrane containing 5 wt. % GO (PBI/sGO-2) showed the highest HT-PEMFC performance. The maximum power density of 364 mW/cm 2 was yielded by PBI/sGO-2 membrane when operating the cell at 160 °C under non humidified conditions. In comparison, a maximum power density of 235 mW/cm 2 was determined by the PBI membrane under the same operating conditions. To investigate the HT-PEMFC stability, long-term stability tests were performed in comparison with the PBI membrane. After a long-term performance test for 200 h, the HT-PEMFC performance loss was obtained as 9% and 13% for PBI/sGO-2 and PBI membranes, respectively. The improved HT-PEMFC performance of PBI/sGO composite membranes suggests that PBI/sGO composites are feasible candidates for HT-PEMFC applications. • This study proposes PBI/sGO as an alternative membrane for HT-PEMFC application. • SGO was revealed as an effective filler for a PBI composite membrane for HT-PEMFC. • PBI/sGO membranes possess high proton conductivity. • PBI/sGO membrane with 5% GO content is a potential electrolyte for HT-PEMFC.

Exergetic Performance Coefficient Analysis and Optimization of a High-Temperature Proton Exchange Membrane Fuel Cell.

Performance of a high-temperature proton exchange membrane fuel cell (HT-PEMFC) and the influence of different parameters on HT-PEMFC is analyzed in this study. Firstly, mathematical expression for energy efficiency, power density, exergy destruction and exergetic performance coefficient (EPC) are derived. Then, the relationship between the dimensionless power density, exergy destruction rate, exergetic performance coefficient (EPC) and energy efficiency is compared. Furthermore, the effect of flow rate, doping level, inlet pressure and film thickness are considered to evaluate the performance of HT-PEMFC. Results show that EPC not only considers exergetic loss rate to minimize exergetic loss, but also considers the power density of HT-PEMFC to maximize its power density and improve its efficiency, so EPC represents a better performance criterion. In addition, increasing inlet pressure and doping level can improve EPC and energy efficiency, respectively.

Effect of multilayer CrN/CrAlN coating on the corrosion and contact resistance behavior of 316L SS bipolar plate for high temperature proton exchange membrane fuel cell

• The CrN/CrAlN coating greatly improved the contact angle and corrosion resistance of 316L SS. • The CrN/CrAlN coating reduced the ICR and increased the surface conductivity of 316LSS. • Single fuel cell test assembled with CrN/CrAlN coating enhanced the performance of HT-PEMFC. Stainless steels have received wide attention as a substitute material for bipolar plates in high temperature proton exchange membrane fuel cell (HT-PEMFC). In the present work, the CrN, CrAlN and multilayer CrN/CrAlN coatings were deposited on 316L SS to increase the corrosion resistance and decrease the interfacial contact resistance. The deposited coatings exhibited face centered cubic phase structure and it was verified from the X-ray diffraction pattern. X-ray photo electron spectroscopy results showed the formation of both CrN and CrAlN layers on 316L SS. CrN/CrAlN coating is more helpful in water management due to low surface roughness and high contact angle in the HT-PEMFC environment. The corrosion resistance behavior of all the samples were studied in 85% H 3 PO 4 solution at 140 °C purged with H 2 (HT-PEMFC anode) and O 2 (HT-PEMFC cathode) gases. The results showed that all the coatings considerably improved the performance of 316L SS and superior corrosion resistance was observed for CrN/CrAlN multilayer coating, whose protective efficiency was 98.12% and 96.14% in the two simulated HT-PEMFC environments. The results of electrochemical impedance spectroscopic studies demonstrated higher impedance for CrN/CrAlN coating. Surface morphological studies performed after corrosion studies revealed that protection ability of CrN/CrAlN coating still remained acceptable. A very low interfacial contact resistance value of 6 mΩ cm 2 at 140 N/cm 2 was observed for CrN/CrAlN coating. Moreover, after corrosion studies, the interfacial contact resistance value of CrN/CrAlN coated 316L was much lower than that of CrN and CrAlN coatings due to the increased oxidation resistance. The maximum power density of about 0.93 W/cm 2 at 2 A/cm 2 and output voltage of 0.96 V was observed for CrN/CrAlN coating.

Fluorination-enabled interface of PtNi electrocatalysts for high-performance high-temperature proton exchange membrane fuel cells

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) bring new opportunities for portable power generation due to their outstanding advantages such as high tolerance to fuel/air impurities and simplified heat/water management. However, carbon-supported nanostructured Pt-based catalysts running at temperatures over 150°C are challenged by the severe aggregation and carbon corrosion, thus leading to poor durability. Herein, we demonstrate that dendritic Pt-Ni nanoparticles supported on fluorinated carbon black (white carbon black) could significantly enhance the performance and durability of HT-PEMFCs as the cathode catalysts running at 160°C due to the strong interaction of the F and Ni atoms to form a NixFy interface on Pt-Ni nanoparticles. With the formation of a stable NixFy interface, this integrated HT-PEMFC reached peak power densities of 906 mW cm−2 and demonstrated excellent durability at 160°C under anhydrous H2/O2 conditions. This mitigation strategy was applied to Pt-alloy/C electrocatalysts and resulted in the elimination of Pt dissolution in practical fuel cells.

Performance of Quaternized Polybenzimidazole-Cross-Linked Poly(vinylbenzyl chloride) Membranes in HT-PEMFCs

High-temperature proton-exchange membrane fuel cells (HT-PEMFCs) are mostly based on acid-doped membranes composed of polybenzimidazole (PBI). A severe drawback of acid-doped membranes is the deterioration of mechanical properties upon increasing acid-doping levels. Cross-linking of different polymers is a way to mitigate stability issues. In this study, a new ion-pair-coordinated membrane (IPM) system with quaternary ammonium groups for the application in HT-PEMFCs is introduced. PBI cross-linked with poly(vinylbenzyl chloride) and quaternized with three amines (DABCO, quinuclidine, and quinuclidinol) are manufactured and compared to the state-of-the-art commercial Dapazol PBI membrane ex situ as well as by evaluating their HT-PEMFC performance. The IPMs show reduced swelling and better mechanical properties upon doping, which enables a reduction in membrane thickness while maintaining a comparably low gas crossover and mechanical stability. The HT-PEMFC based on the best-performing IPM reaches up to 530 mW cm-2 at 180 °C under H2/air conditions at ambient pressure, while Dapazol is limited to less than 430 mW cm-2 at equal parameters. This new IPM system requires less acid doping than conventional PBI membranes while outperforming conventional PBI membranes, which renders these new membranes promising candidates for application in HT-PEMFCs.