Proton Conductivity Of Membranes Research Articles

High‐Throughput Electrospinning of Unmodified and Aminated Poly(Pentafluorostyrene) for Fiber‐Reinforced Proton Exchange Membranes

AbstractThis study demonstrates a high‐throughput fabrication of fiber interlayers for proton exchange membranes based on poly(pentafluorostyrene) (PPFSt) and its aminated derivatives. The fibers are produced by electrospinning, where the parameters are carefully screened. The controlled parameters are solvent composition, weight percentage, voltage, flow rate, and temperature, controlled with a self‐designed heating jacket. The parameters are iterated toward optimized fiber structure and maximum output. The yielded fibers are infiltrated with Nafion and sulfonated polymer from bisphenol AF and decafluorobiphenyl (SFS001) by spray‐coating and doctor blading to obtain the fiber‐reinforced proton exchange membranes. Tensile tests reveal a higher Young's modulus and yield stress than pure Nafion. Here, the basicity of the aminated PPFSt fibers correlates with the Young's modulus due to improved acid‐base interactions between amine groups and sulfonic acid. The acid‐base interactions influence the composite membrane's proton conductivity, varying from 23 mS cm−1 for strongly alkaline fibers to 69 mS cm−1 for non‐basic fibers. These findings can be transferred to fabricating fiber reinforcements beyond routinely used poly(benzimidazoles).

Dissected antiporter modules establish minimal proton-conduction elements of the respiratory complex I

The respiratory Complex I is a highly intricate redox-driven proton pump that powers oxidative phosphorylation across all domains of life. Yet, despite major efforts in recent decades, its long-range energy transduction principles remain highly debated. We create here minimal proton-conducting membrane modules by engineering and dissecting the key elements of the bacterial Complex I. By combining biophysical, biochemical, and computational experiments, we show that the isolated antiporter-like modules of Complex I comprise all functional elements required for conducting protons across proteoliposome membranes. We find that the rate of proton conduction is controlled by conformational changes of buried ion-pairs that modulate the reaction barriers by electric field effects. The proton conduction is also modulated by bulky residues along the proton channels that are key for establishing a tightly coupled proton pumping machinery in Complex I. Our findings provide direct experimental evidence that the individual antiporter modules are responsible for the proton transport activity of Complex I. On a general level, our findings highlight electrostatic and conformational coupling mechanisms in the modular energy-transduction machinery of Complex I with distinct similarities to other enzymes.

Cross-Linking of Bromo-Pillar[5]arenes and Sulfonated Poly(Aryl Ether Ketone Sulfone) Enhances Proton Conductivity of Membranes at Low Ion Exchange Capacity

Cross-Linking of Bromo-Pillar[5]arenes and Sulfonated Poly(Aryl Ether Ketone Sulfone) Enhances Proton Conductivity of Membranes at Low Ion Exchange Capacity

Tailored proton conductive membranes of PVdF-co-HFP: Investigating the synergistic effects of ammonium tetrafluoroborate and phosphoric acid dopants on dielectric characteristics

This study investigates the structural, thermal, and dielectric properties of pure PVdF-co-HFP matrix and its composite electrolytes, PVdF-co-HFP/NH4BF4[x], both before and after PA doping, using FTIR, SEM, TGA, and dielectric analyses. FTIR spectra reveal characteristic vibrational bands, confirming the presence of various functional groups and phases. SEM images display a smooth and homogeneous surface morphology for pure PVdF-co-HFP, while the composite electrolytes exhibit irregular dispersion of NH4BF4 salt and rougher surfaces upon PA doping. TGA analysis shows that the onset of thermal degradation occurs at approximately 370 ℃ for pure PVdF-co-HFP, while PA-doped samples demonstrate higher decomposition temperatures, exceeding 400 ℃ due to hydrogen bonding and ionic complex formation. The presence of NH4BF4 and PA doping also affects the crystallinity of the PVdF-co-HFP matrix, notably shifting the transition temperatures of the alpha and beta phases. Ionic conductivity measurements indicate that PA doping significantly enhances conductivity by increasing charge carrier concentration and facilitating ion transport. PA-doped PVdF-co-HFP/NH4BF4[10] showed the highest conductivity reaching 1.68 × 10−3 S.cm−1 at 1 MHz and 400 K. Dielectric studies reveal frequency-dependent behavior, with dielectric constant (ε') and loss (ε") showing distinct trends influenced by salt concentration and PA doping. The dielectric tangent loss (tanδ) of PA-doped PVdF-co-HFP/NH4BF4 composite membranes exhibits frequency and temperature dependence. At higher temperatures, tanδ increases with frequency, showing a resonance peak that shifts towards higher frequencies. The study elucidates the impact of PA doping on the structural, thermal, and electrochemical performance of PVdF-co-HFP/NH4BF4 composites, providing insights for their potential applications in advanced electrolyte systems.

Investigation on sulfonated PVC/polymethyl methacrylate (PMMA)/polystyrene sulfonate (PSS) polymer blends as proton-conducting membrane

AbstractThe design and development of cost-effective and increased methanol permeable and proton-conductive membranes are critical concerns in the fabrication of polymeric electrolyte membranes (PEM). A solution-casting process was used to create a low-cost PEM based on sulfonated polyvinyl chloride (SPVC)-Polymethyl methacrylate (PMMA) blended with varying concentrations of Poly(sodium 4-styrenesulfonate) (PSS). The contact angle, oxidative stability, swelling ratio, water uptake, and methanol uptake of SPVC/PMMA/PSS membranes were investigated as a function of PSS molar ratio. FT-IR examination, 1H NMR spectra, Raman spectroscopy, X-ray diffraction, thermogravimetric analysis (TGA), and scanning electron microscope micrographs were additionally utilized for confirming the chemical structure, morphology, and thermal stability of SPVC/PMMA/PSS membranes. Furthermore, the ion exchange capacity (IEC), proton conductivity, and methanol permeability of SPVC/PMMA/PSS membranes were investigated depending on the PSS concentration. The results showed a significant increase in proton conductivity from 1.80 × 10–2 for SPVC/PMMA/1%PSS to 4.7 × 10–2 S/cm for SPVC/PMMA/5%PSS at ambient temperature. On the other hand, the methanol permeability (P = 8.53 × 10–8 cm2/s) was noticeably lower than that of Nafion 117 (3.39 × 10–6 cm2/s). Additionally, the IEC of the manufactured membrane was 1.38 ± 0.7 meq g−1 for SPVC/PMMA/5%PSS compared to 0.91 meq g−1 for Nafion 117 membranes. The maximum water uptake of the synthesized membranes was 48.37 ± 2.27%, whereas Nafion 117 membrane absorption was 65.44%. According to conductivity studies and the membrane efficiency factor, the ideal PSS content in a polymer matrix is 4 wt.%. Finally, the developed SPVC/PMMA/PSS polyelectrolytic membranes show improvements in essential properties such as methanol permeability, proton conductivity, and IEC when combined with low-cost materials, making them an attractive contender as PEM for DMFCs. Graphical abstract

Proton conductivity and durability of Ce-based hybrid proton exchange membranes synchronously enhanced by dual-function γ-AlOOH@Ti-supported CeO2 composite oxide

To enhance the proton conductivity and durability of Ce-based hybrid proton exchange membranes (PEMs), this study fabricates modified perfluorosulfonic acid (PFSA) hybrid membranes by incorporating the dual-function γ-AlOOH@Ti-supported CeO2 composite oxide (γ-AlOOH@Ti/CeO2). In addition to combining the inherent proton conductivity of γ-AlOOH with the excellent radical scavenging ability of CeO2, both the proton conductivity and durability of Ce-based PEMs are further improved by introducing Ti-dopant, which not only increases hydrogen vacancies on the surface of γ-AlOOH, which facilitate proton conduction, and induces electron transfer from γ-AlOOH@Ti to CeO2, which enhance free radical adsorption. As results shown, the proton conductivity and the fluoride release value of the resulting hybrid membrane are about 76 % higher and 35.25 % lower than those of the PFSA-CeO2 membrane, respectively. Moreover, the performance of cells shows that, after accelerated degradation testing, the PFSA-γ-AlOOH@Ti/CeO2 membrane exhibits the lowest peak power density decrease rate, the impedance increase rate and hydrogen crossover current density, with 11.79 %, 27.54 % and 3.04 mA cm−2, respectively. These results suggest that compared to CeO2-hybrid PEMs, γ-AlOOH@Ti/CeO2-based hybrid PEMs exhibit higher proton conductivity and superior chemical stability, indicating the potential application of γ-AlOOH@Ti/CeO2-based hybrid PEMs in proton exchange membrane fuel cells.

Nitrogen-Rich Covalent Organic Frameworks Composited High-Temperature Proton Exchange Membranes with Ultralow Volume Expansion and Reduced Phosphoric Acid Leakage.

Phosphoric acid (PA) leakage and volume expansion are critical factors limiting long-term stable operation of PA-doped polybenzimidazole (PBI) for high-temperature proton exchange membrane fuel cells. Enhancing the interaction between the polymer matrix and PA provides an effective way to minimize PA loss and inhibit excessive membrane swelling. The covalent organic frameworks (COFs) are helpful in improving the performance of PA-PBI membranes due to the robust frameworks, adjustable structures, and good compatibility with polymers. Here, in this work, we synthesized porous COFs named TTA-DFP containing triazine rings and pyridine groups at room temperature for as short as 2 h without oxygen isolation. TTA-DFP was then blended with commercial poly[2,2'-(p-oxidiphenylene)-5,5'-benzimidazole] (OPBI) to prepare composite membranes. The abundant alkaline N sites in TTA-DFP exhibit strong interactions with PA and OPBI, which not only provide more proton transport pathways to promote proton conduction but also immobilize PA in acidophilic micropores to reduce PA leakage. The composite membranes exhibit a much lower volume swelling ratio than that of the OPBI membrane. The PA retention of the composite membrane after 120 h of treatment at 80 °C and 40% relative humidity can reach as high as 84.6%. Particularly, the proton conductivity of the composite membrane doped with 15 wt% TTA-DFP achieves 0.112 S cm-1 at 180 °C without humidification with a swelling ratio of 24.1%. In addition, it has an optimal peak power density of 824.4 mW cm-2 at 180 °C, which is 1.7 times that of the OPBI membrane. The stability of the composite membrane is much better than that of OPBI at a current density of 0.3 A cm-2 at 140 °C for 120 h.

Sulfonating and polyhedral oligomeric silsesquioxane crosslinking in one step to build multiple proton pathways for proton exchange membrane fuel cells over a wide temperature range

Developing proton exchange membrane fuel cells (PEMFCs) operating over a wide temperature range can avoid additional internal/external heating or cooling devices for the PEMFCs operating. Polybenzimidazole (PBI) doped with phosphoric acid (PA) exhibits significant potential in high-temperature proton exchange membrane fuel cells (HT-PEMFCs). Nevertheless, the traditional PA-PBI membranes are limited to operating within 140∼180 °C. In this work, a sulfonated polyhedral oligomeric silsesquioxane crosslinked polybenzimidazole membrane enriched pyridine and diazafluorene (CSPBI-X) is prepared where the sulfonation and crosslinking are accomplished by one-step heating. The theoretical calculations confirm that PA molecules have strong interactions with sulfonic acid groups and nitrogen-containing groups, enabling the membrane to achieve proton conductivity in a wide temperature range (80–180 °C). Moreover, the cross-linked sulfonated membranes have excellent PA retention ratio as high as 83.8% under 80 °C and 40% relative humidity for 120 h. Remarkably, with the acid doping level of 7.6, the proton conductivity of the CSPBI-20 membrane reaches 0.0491 S cm−1 and 0.145 S cm−1 at 80 °C and 180 °C in dry state, respectively. The highest power density of the CSPBI-20 at 80, 100, 120, 140, 160, and 180 °C is 257.3, 362.9, 485.3, 604.6, 755.3, and 956.1 mW cm−2, respectively.

Proton-Conducting Polyelectrolyte Membranes Containing Graphene Dots for Moisture Electric Generators

Proton-Conducting Polyelectrolyte Membranes Containing Graphene Dots for Moisture Electric Generators

Adipic acid-mediated hydrogen bonding network allocation for efficient proton conduction in water-stabilized lamellar MOF membranes

The poor water-stability and cross-layer proton transfer property pose a challenge to the lamellar metal–organic frameworks (MOFs) membrane when acting as a promising proton exchange membrane. Herein, we report an adipic acid-mediated strategy to improve the water-stability and the cross-layer proton conductivity of CuTCPP lamellar MOF membrane, which achieves a maximum power density and current density of 112.6 mW cm−2 and 424.4 mA cm−2, respectively. Adipic acid with extra functional groups (–PO3H2, –COOH) stably bridges the adjacent crystal layers via the terminal carboxylic acid anchoring Cu sites. In particular, the extra functional groups introduced into the adipic acid regulate the allocation of hydrogen bonding networks in an umbrella-shape around adipic acid with copper-porphyrin structures as external margin, enriching the coherence of hydrogen bonding network on the proton transport path. Benefiting from the regular pore structure of MOF, the optimized hydrogen bonding networks in adjacent crystal layers construct a more abundant through-plane transfer pathway. The resultant through-plane proton conductivities of CuTCPP-PO3H2/–COOH membranes are up to 108/89 mS cm−1 at 80 °C and 100 % RH, which is ∼ 6-fold higher than that of the pristine CuTCPP membrane (13 mS cm−1), with a conductivity attenuation of < 5 % during a humidity cycling test for 12 times.

Nanocomposite polyphenyleneoxide with amino-functionalized silica: structural characterization based on thermal analysis

AbstractA polymer nanocomposite based on sulfonated polyphenylene oxide with amino-functionalized mesoporous silica was designed, synthesized, and tested as a new material for proton exchange membrane (PEM preparation. Characterization of the intermediate and final products of synthesis was realized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and thermal analysis. Broadband Dielectric Spectroscopy (BDS) was used to determine dielectric properties including ionic conductivity. Thermogravimetric analysis has provided important information regarding the composition and thermal stability of the three compounds, subject to thermal degradation: 1) the amino-silica with cetyltrimethylammonium bromide (CTAB) template inside the pores (MS-NH2I), 2) the mesoporous amino-silica after removing the template (MS-NH2II) and 3) the polymer nanocomposite (sPPO-MS-NH2). The thermal decomposition of the composite samples occurs in three stages: in the first, up to 150 °C, water and organic solvents were lost; the second stage, between 200-300 °C, was due to breaking the organic functionalities (-NH2, amino and -SO3H, sulfonic acid), and the third stage, above 400 °C was due to polymer chain degradation. The final residue at 700 °C reflects the contribution of inorganic silica. The proton conductivity, for polymeric (sPPO) and composite (sPPO-MS-NH2) membranes was determined from BDS dates, both in dry and hydrated states. For dried samples, the higher values of proton conductivities were: 0.16 mS cm−1 (sPPO, 70 °C) and 0.03 mS cm−1 (sPPO-MS-NH2, 120 °C), and the higher values of proton conductivity increased for the hydrated samples with two orders of magnitude: 36.5 mS cm−1 (sPPO, 40 °C) and 22.4 mS cm−1 (sPPO-MS-NH2, 50 °C). However, the proton conductivity is still dependent on the hydration state, even for the composite membrane.

The Effect of Water Quality on PEM Electrolyzer Performance

There has been growing interest in the use of removable, clean, and sustainable energy sources as a solution to eliminate environmental problems caused by fossil fuels. In particular, the electrolysis of water to produce green hydrogen is one of the most promising technologies. Among various electrolysis techniques, proton exchange membrane water electrolyzer (PEMWE) stands out as the most promising for mobility and large-scale energy-storage applications (1). Hydrogen production by PEMWEs requires approximately 45 kg of high-quality water to produce 5 kg of hydrogen. It has been estimated that about 22% of the total cost of a state-of-the-art PEMWE system is for water deionization treatment (2). This water purity requirement is not only an economic barrier, but also a constraint for the use of this system in areas where high-quality water is not accessible or in areas where water for human consumption is a scarce resource. Therefore, studying the effect of water quality on PEMWE performance is an important first step in identifying key degradation mechanisms on the path to discovering new PEMWE architectures that are more tolerant of poor-quality feed waters.In this work, the effect of common impurities, such as Na+ and Mg2+, in feed water on the performance of common PEMWE architectures is studied. The main goals of the work are: 1) to understand the tolerance range for long term operation, 2) to identify major degradation mechanisms when the failure occurs. Experiments were carried out in an electrolyzer equipped with platinized Ti electrodes, IrO2 and Pt/C as anodic and cathodic catalysts, respectively, and a 115 Nafion® membrane. Durability studies of 100-hour duration and electrochemical characterization of the electrolyzer at different time intervals (polarization curves and impedance spectroscopy) were performed. The membrane/electrode assembly was probed by SEM /EDX before and after the experiments and cation concentrations in the water were monitored by ICP. An electrochemical model is proposed to explain the observed behavior of the electrolyzer with DI water and in the presence of impurities.The results show that the presence of cations affects the performance of the electrolyzer at different levels depending on the concentration of the cation and its valence (Mg2+ > Na+ >DI water). Mg+2 had the same effect as Na+ even at 5 times lower concentration. Cations have higher affinity than protons for sulfonic acid groups (-SO3 -), leading to a displacement of protons and a consequent reduction in the membrane proton conductivity. However. according to the polarization curves, there are effects beyond the ohmic potential due to the increase in membrane resistance. The major effect of cations is on the reaction kinetics, which is the primary reason for the observed increase in cell voltage. The presence of cations within the membrane blocks the transport of protons, which creates a lack of protons at the cathode, resulting in the kinetic change from proton reduction to reduction of water. Moreover, the EDX results showed that Na+ and Mg2+ ions transfer from anode to cathode and deposit on the membrane and catalyst layers, which may cover the active catalyst sites, block the proton transport inside the membrane and degrade the catalyst ionomer layers.References Sazali N. Emerging technologies by hydrogen: A review. International Journal of Hydrogen Energy. 2020 (45): 18753-18771Becker H, Murawski J, Shinde DV, Stephens IEL, Hinds G, Smith G. Impact of impurities on water electrolysis: A review. Sustainable Energy & Fuels. 2023;7(7):1565-603.

(Invited) Comparison of Catalyst-Coated Electrodes vs. Catalyst-Coated Membranes in PEM Water Electrolysis Cells

The PEM (Proton-Exchange Membrane or Polymer Electrolyte Membrane) cell concept [1] is used in fuel cells and water electrolysis cells. PEM water electrolysis is a compact, efficient and flexible technology for the production of “green-hydrogen” from renewable (intermittent) energy sources. The unit cell (Figure 1) is made of several adjacent functional layers: (i) the proton-conducting polymer membrane (1); (ii) two catalysts layers (CLs) for hydrogen/oxygen evolution containing platinum group metals or PGMs (2;2’); (iii) a porous transport layer used for mass transport of reactants/products and electricity distribution (3;3’); (iv) water flow fields for water circulation (4;4’); bipolar plates (5;5’). From a practical viewpoint, the CLs can be deposited on either side of the interfaces formed between the polymer membrane and the porous transport layer: (i) on the supporting porous transport layers to form catalyst-coated electrodes which are then hot pressed against the bare membrane to form membrane – electrode assemblies; (ii) directly onto the membrane to form catalyst-coated membranes (CCM).The aim of this paper is to evaluate the efficiency and durability of both concepts, drawing on recent advances in manufacturing techniques to reduce the loading of PGM catalysts.[1] W.T. Grubb Jr., Batteries with Solid Ion-Exchange Electrolytes. Journal of the Electrochemical Society. 106 (1959) 275-279.[2] C. Rozain, P. Millet, Electrochemical characterization of Polymer Electrolyte Membrane Water Electrolysis Cells, Electrochimica Acta, 131 (2014) 160-167. Figure 1. Schematic diagram showing the cross-section of a PEM water electrolysis cell [2]. Figure 1

Direct Non-Oxidative Methane Conversion and Hydrogen Co-Production in a Proton Conducting Membrane Reactor

Direct Non-oxidation Methane Conversion (DMNC) has been recognized a promising technology for the upgrading of cheap and abundant methane to higher hydrocarbons (C2+) and H2, but this technology has not been commercialized yet because of the low methane equilibrium conversion and severe carbon deposition.1-3 Here, we present our effort to develop a proton conducting membrane reactor (SrCe0.7Zr0.2Eu0.1O3- ⴃ) combined with the catalysts (Fe©SiO2) to circumvent the equilibrium limitations of the DMNC reaction and solve the coking (i.e., solid carbon deposition) problem. By coupling the Fe©SiO2 catalysts with H2 permeable membrane reactor, part of produced H2 during the catalytic conversion can be extracted from the effluent gas, which not only provides a one-step hydrogen production without additional separation process, but also shifts the equilibrium of the reaction to the product side and achieves an improved methane conversion and higher C2+ yield when compared to the traditional fixed-bed reactor. In addition, an air sweep outside the reactor results in O-permeation into catalyst to oxidize any deposited carbon to CO thus preventing coking.The membranes were fabricated using tape casting of the support layer followed by dip coating process to form the dense membrane layer. Using this method, we obtained 25 µm for the thickness of the dense layer and around 700 µm for the thickness of the support layer (see Fig. 1a and 1b). The catalyst was synthesized by a simple sol-gel method followed by fusing process, and then was crushed into 40-80 mesh and loaded inside of membrane reactor to test.The performance metrics include methane conversion, selectivity, and product yield. Our membrane reactor achieved single-pass methane conversion of 17.5%, and a C2+ yield of 15% (see Fig. 1c) at 1323K.Finally, our membrane reactors were stable for over 350 hours, which, along with the aforementioned performance metrics, constitutes a major advance in the development of commercial DMNC technology. References Guo, X.; Fang, G.; Li, G.; Ma, H.; Fan, H.; Yu, L.; Ma, C.; Wu, X.; Deng, D.; Wei, M.; Tan, D.; Si, R.; Zhang, S.; Li, J.; Sun, L.; Tang, Z.; Pan, X.; Bao, X., Direct Nonoxidative Conversion of Methane to Ethylene, Aromatics, and Hydrogen. Science 2014, 344 (6184), 616-619.Thyssen, V. V.; Vilela, V. B.; de Florio, D. Z.; Ferlauto, A. S.; Fonseca, F. C., Direct Conversion of Methane to C2 Hydrocarbons in Solid-State Membrane Reactors at High Temperatures. Chemical Reviews 2022, 122 (3), 3966-3995.Sakbodin, M.; Schulman, E.; Cheng, S.; Huang, Y.-L.; Pan, Y.; Albertus, P.; Wachsman, E. D.; Liu, D., Direct Nonoxidative Methane Conversion in an Autothermal Hydrogen-Permeable Membrane Reactor. Advanced Energy Materials 2021, 11 (46), 2102782. Figure 1

(Invited) Overview of Ion-Conducting Polymer Membranes and Membrane Separators for Water Electrolysis

Traditional liquid alkaline electrolyzer uses a porous diaphragm to allow diffusion of hydroxide ion from a feed of concentrated KOH solution while separating anode and cathode and suppressing mixing of produced H2 and O2 gases. Although liquid alkaline electrolyzer is considered as a matured technology, recent renaissance of new electrode separators suggests there is significant potential for improvement in efficiency and cost reduction by lowering area specific resistance and increasing operation current density.Ion-conducting polymers (e.g., proton or hydroxide) are used as a key component of polymer electrolyte membranes, such as acidic proton exchange membrane (PEM) and alkaline anion exchange membrane (AEM), in electrochemical energy conversion and storage technologies including water electrolyzers. For example, the state-of-the-art PEM electrolyzers have used Nafion for a PEM and ionomer catalyst binder for decades, though it is not ideal proton-conducting membrane material for those applications. Recent pressure on perfluoroalkyl substrates (PFASs) from government and environmental activist groups due to their environmental and health hazard has attracted the development of alternative polymer electrolyte membranes based on hydrocarbon polymers within electrochemical society. Compared to perfluorosulfonated Nafion, hydrocarbon ion-conducting polymers (both PEMs and AEMs) can offer advantages of flexible synthetic tunability, lower gas permeability, and importantly lower production cost.In this tutorial, an overview of recent progress in the development of advanced porous membrane separators, PEMs and AEMs, their key membrane properties, and the state-of-the-art performance in applications of water electrolyzers will be discussed. Figure 1

Synergistic Molecular Alignment and Dipole Polarization in Stretched Nafion/Poly(vinylidene fluoride) Blend Membranes for High Proton Conduction in PEMFCs.

The nanostructure of Nafion and poly(vinylidene fluoride) (PVDF) blend membranes is successfully aligned through a mechanical uniaxial stretching method. The phase-separated morphology of Nafion molecules distinctly forms hydrophilic proton channels with increased connectivity, resulting in enhanced proton conductivity. Additionally, the crystalline phase of PVDF molecules undergoes a successful transformation from the α- to β-phase during membrane stretching, demonstrating an alignment of fluorine and hydrogen atoms with a TTTT(trans) structure. The aligned nanostructure of the blend film, combined with the dipole polarization of the β-phase PVDF, synergistically enhances the proton conduction through the membrane for operating proton-exchange membrane fuel cells (PEMFCs). The controlled structures of the blend membranes are thoroughly investigated using atomic force microscopy and small-angle X-ray scattering. Furthermore, the improved in-plane proton conductivity facilitates increased proton conduction at the interface between the membrane and catalyst layer in the membrane-electrode assembly, ultimately enhancing the power generation of PEMFCs.

The Incorporation of Sulfonated PAF Enhances the Proton Conductivity of Nafion Membranes at High Temperatures.

Nafion membranes are widely used as proton exchange membranes, but their proton conductivity deteriorates in high-temperature environments due to the loss of water molecules. To address this challenge, we propose the utilization of porous aromatic frameworks (PAFs) as a potential solution. PAFs exhibit remarkable characteristics, such as a high specific surface area and porosity, and their porous channels can be post-synthesized. Here, a novel approach was employed to synthesize a PAF material, designated as PAF-45D, which exhibits a specific surface area of 1571.9 m2·g-1 and possesses the added benefits of facile synthesis and a low cost. Subsequently, sulfonation treatment was applied to PAF-45D in order to introduce sulfonic acid groups into its pores, resulting in the formation of PAF-45DS. The successful incorporation of sulfonic groups was confirmed through TG, IR, and EDS analyses. Furthermore, a novel Nafion composite membrane was prepared by incorporating PAF-45DS. The Nyquist plot of the composite membranes demonstrates that the sulfonated PAF-45DS material can enhance the proton conductivity of Nafion membranes at high temperatures. Specifically, under identical film formation conditions, doping with a 4% mass fraction of PAF-45DS, the conductivity of the Nafion composite membrane increased remarkably from 2.25 × 10-3 S·cm-1 to 5.67 × 10-3 S·cm-1, nearly 2.5 times higher. Such promising and cost-effective materials could be envisioned for application in the field of Nafion composite membranes.

Imine–linked covalent organic framework synthesis

Imine-linked covalent organic frameworks (COFs) are highly ordered polymer networks that are more chemically stable compared to their boron-linked counterparts making them more attractive for a variety of applications, including as energy storage devices, proton-conductive membranes, and catalytic supports. Furthermore, these imines linked COFs may be synthesized using a diverse spectrum of monomers, providing tremendous design freedom and versatility. We report a general method for synthesizing Imine linked COFs based on the Schiff-base condensation reaction of anilines. The synthesis of 4,4′,4′′-(benzene-1,3,5-triyltris(ethyne-2,1-diyl) trianiline, 4,4′-dicarbaldehyde, 4,4′-(ethyne-1,2-diyl) dibenzaldehyde (BPDA), and terephthalaldehyde (PDA) monomers produced by multistep coupling processes.

Improving the performance and long-term durability of high-temperature PEMFCs: A polyvinylpyrrolidone grafting modification strategy of polybenzimidazole membrane

This study introduces an innovative approach to graft Polyvinylpyrrolidone (PVP) onto Polybenzimidazole (PBI) to synthesise Proton Exchange Membranes (PEMs) with high performance and durability. As a widely used hydrophilic polymer in industry, PVP can add numerous nitrogen-containing functional groups to the membrane to enhance its phosphoric acid (PA) binding ability. In this work, Polybenzimidazole-graft-polyvinylpyrrolidone (PVP-g-PBI) polymers with varying grafting degrees were synthesized and tested to investigate the impact of the grafting modification on the membrane's proton conductivity, thermal properties, and electrochemical performance. With the introduction of PVP side chains, the fuel cell showed enhanced PA uptake and substantial improvements in peak power density. Notably, PBI-g-PVP membranes with a grafting degree of 22.4 % achieved a peak power density enhancement up to 1312 mW cm⁻2 at 160 °C, a 59.6 % increase over pristine PBI membranes. Due to the increased PA binding sites in the membrane, the PBI-g-PVP PEMs exhibit better PA adsorption ability and long-term durability than pristine membranes. The accelerated stress test (AST) demonstrated that the PBI-g-PVP membranes maintain a peak power density of 1105 mW cm⁻2 after a 70-h test, equivalent to 183.9 % of the pristine PBI membrane. The improved fuel cell performance and durability of PBI-g-PVP PEMs underscore the potential of this grafting strategy.

High performance and robust durability proton conductive composite membranes containing CeO2-TiC incorporated sulfonated poly(arylene ether) for hydrogen fuel cells

Degradation of proton exchange membrane (PEM) due to free radicals often decreases the overall performance of proton exchange membrane fuel cells (PEMFC). The incorporation of antioxidative additives into the polymer matrix has been widely exploited to mitigate oxidative degradation but is still challenging. Herein, butylsulfonated poly(arylene ether)(SAFPAE) was synthesized by polycondensation followed by nucleophilic substitution and highly crystalline CeO2-TiC filler was prepared by simple hydrothermal process. SAFPAE alleviates the problematic characteristics of proton-exchange membranes (PEMs) whereas CeO2 scavenges free radicals and TiC improves tensile strength. Variable weight ratios of CeO2-TiC were blended into the SAFPAE matrix to study its physicochemical, and electrochemical properties. The random distribution of CeO2-TiC in the SAFPAE matrix enhanced thermal and mechanical strength and increased water absorption, ion exchange capacity, as well as proton conductivity. Specifically, SAFPAE/CeO2-TiC (1.0 wt%) exhibited a current output of 0.18 A cm−2 and a power output of 0.087 Wcm−2 at 20 % RH and 60°C. It also experienced a degradation of 0.145 mV h−1 over 1100 hours of operation. Under operating conditions of RH 20 % and 60°C, PEMFCs with SAFPAE/CeO2-TiC (1.0 wt%) membrane exhibited significantly improved performance and enhanced durability compared to PEMFCs with pure SAFPAE and without sacrificing their cell performance.