Ion Exchange Capacity Values Research Articles

Ionic Polybenzimidazoles Crosslinked through Thiol-Ene Reactions for Anion Exchange Membranes

This research introduces a study outlining the synthesis and characteristics of innovative anion exchange membranes that utilize m-polybenzimidazole (m-PBI) as the polymer backbone structure. These membranes incorporate quaternary ammonium groups and alkene groups as side chains. These ionic m-PBI membranes were further crosslinked through thermal thiol-ene reactions. By adeptly manipulating the quantities of attached quaternary ammonium groups and alkene groups, the ion exchange capacity (IEC) values and crosslinking degrees were independently controlled. A comprehensive range of m-PBI based anion exchange membranes was developed, showcasing IEC values ranging from 1.51 to 2.50 mmol/g. This series of membranes demonstrated hydroxide conductivity levels ranging between 14 and 58 mS/cm at an operational temperature of 80 °C. Particularly noteworthy is the comparison between membranes with similar IEC values: the crosslinked membranes exhibited reduced water absorption while effectively maintaining a level of hydroxide conductivity comparable to that of uncrosslinked membranes. Moreover, the crosslinked membranes exhibited enhanced dimensional stability. An intriguing finding emerged from a crosslinked membrane with an IEC value of 2.46 mmol/g, which retained a remarkable 84% of its original hydroxide conductivity after being immersed in a 1.0 M sodium hydroxide solution at 60 °C for a duration of 720 hours. These membranes demonstrated mechanical strength even in their hydrated state, exhibiting tensile strengths ranging from 10.8 to 14.6 MPa. Given their heightened hydroxide conductivity, improved resistance to alkaline conditions, and favorable mechanical attributes, the crosslinked ionic m-PBIs emerge as promising candidates for anion exchange membranes in fuel cell applications. Keywords ; anion exchange membranes, crosslinking reaction, polybenzimidazole, back titration, mechanical strength.

Tailoring physicochemical properties of quaternized polystyrene-ethylene/butylene-styrene membrane for enhanced pervaporation desalination

Pervaporation offers unique advantages for desalination of hypersaline water using highly hydrophilic and selective membrane. Positively charged membrane is superior in repelling cations and preventing scaling through electrostatic repulsion. This study investigates the quaternization and crosslinking of block copolymer styrene-ethylene-butylene-styrene (SEBS) membrane and explores the potential of quaternized membrane for pervaporation desalination. A one-step immersion process was proposed to easily adjust the physicochemical properties of membrane using trimethylamine (TMA) and N,N,N′,N′-tetramethyl-1,6-hexanediamine (TMHDA) for ammonium grafting and crosslinking. Compared to the quaternization with TMA or TMHDA alone, the combination of TMA and TMHDA produces a synergistic effect, improving crosslinking efficiency and facilitating the grafting reaction. This results in high ion exchange capacity (IEC) values and a transformation of microphase separation structure with more interconnected hydrophilic domains. An ultrahigh water permeability coefficient of 0.6 × 106–1.2 × 106 Barrer and highly intrinsic salt rejection were obtained in treating 3.5–20 wt% NaCl solution. The thin film composite QEBS/nylon membranes showed a superior water flux of 116.5 kg·m−2·h−1 and salt rejection of >99.99 % in desalinating 5 wt% NaCl solution at 85 °C. Additionally, the membrane exhibited excellent long-term performance stability and resistance to acid and alkali environment, showing great potential for desalination of hypersaline water.

Rapid removal of polycyclic aromatic hydrocarbons from water using sulfonated mesoporous polymeric adsorbents

Polycyclic aromatic hydrocarbons (PAHs) are potential hazards and are often found in aquatic environments through industrial effluents. Herein, we report sulfonated modified mesoporous thermoplastic polymers to remove potentially carcinogenic PAHs from water rapidly. Mesoporous structures of the thermoplastics (polystyrene, polysulfone, and polycarbonate) were attained using nano-crystallization induced phase separation by flash-freezing route. Sulfonation reactions carried out hydrophilic surface modifications of the polymers. Their ion exchange capacity (IEC) values determined the degree of sulfonation. The sulfonated mesoporous polymers were characterized using Fourier-Transform Infra-Red spectroscopy (FT-IR) for functional groups, Field-Emission Scanning Electron Microscopy (FE-SEM) for mesoporous structures, Brunauer-Emmet-Teller method for specific surface area, and Barrett-Joyner-Halenda method for pore size distributions. The IEC values for the sulfonated mesoporous polymers range from 1.13 – 1.15 × 10-2 meq. g−1. The sulfonated mesoporous polymers showed high specific surface areas (176–185 m2/g) with pore sizes ranging from 5 nm to 9 nm. The sulfonated mesoporous polymers rapidly adsorb PAHs from nearly saturated water solutions within 60 min with % removal of over 98 %. The adsorbents can also be easily regenerated by simple washing with methanol and are found to be recycled up to 10 cycles with only a marginal reduction in adsorption capacities.

Ion-Exchange Strategy Enabling Direct Reformation of Unreliable Perfluorinated Cationic Polymer for Robust Proton Exchange Membrane towards Hydrogen Fuel Cells

Perfluorosulfonated anionic ionomers are known for their robust ion conductivity and chemical and mechanical stability. However, the structure and transport property degradation of perfluorinated cationic polymers (PfCPs) are not well understood. Herein, we propose an ion-exchange strategy to identify the structural degradation, ion transport mechanisms, and architectural reformation of PfCPs. Particularly, we demonstrate that the utility of a –SO2–N+ strategy employing the Menshutkin reaction cannot yield reliable PfCPs and anion-exchange membranes, but can yield an unreliable zwitterionic intermediate (cations–anions molar ratio is approximately 7.6%). Moreover, the degradation products were efficiently reformed as proton exchange membranes (PEMs), and the as-reformed PEMs achieved an ion-exchange capacity (IEC) value (0.89 mmol g−1), meanwhile retaining more than 94.7% of their initial capacity. Furthermore, the fuel cell assembled with reformed PEMs displayed a power density of 0.91 Wcm−2 at 2.32 A cm−2, which was 90.1% of that of the robust perfluorosulfonic acid PEMs. Our combined findings shed some fresh light on the state of understanding of the structure–property relationship in PfCPs.

Design and synthesis of poly(styrene-b-(ethylene-co-butadiene)-b-styrene) anion exchange membranes with high ion conductivity

Poly(styrene-b-(ethylene-co-butadiene)-b-styrene) copolymers (SEBS) have garnered significant attention to develop anion exchange membranes (AEMs) for fuel cells. However, SEBS commodities encounter a formidable obstacle of fabricating high-performance AEMs as thermoplastic elastomer. Herein, a series of poly(styrene-b-butadiene-b-styrene) copolymers (SBS) with high content of 1,4-butadiene units (>90 % of middle block) and variable content of polystyrene (PS, 51.3, 61.6 and 70.7 wt%) has been designed to develop SEBS AEMs with high-strength polyethylene phase via hydrogenation, chloromethylation, quaternization and alkalization. The results demonstrate that high PS content broadens the ion transport channel, improves the ion exchange capacity (IEC) and alkali resistance stability, and substantially boosts the ion conductivity, water uptake and swelling ratio of AEMs. Besides, the high proportion of polyethylene phase from 1,4-butadiene unit of SBS copolymers provides good dimensional stability to the AEMs. Remarkably, the AEMs with 70.7 wt% PS and an IEC value of 3.37 mmol g−1 significantly upgrades the ionic conductivity to ∼190 mS cm−1 at 80 °C. It attains a peak power density of ∼1000 mW cm−2 at 2.09 A cm−2 in a H2/O2 single cell operating at 80 °C. This outstanding performance underscores the promising potential of such SEBS copolymers in the development of high-performance SEBS AEMs for fuel cells.

Anisotropic polyphenylene-based anion-exchange membranes with flexible side-chains via click reaction for high-performance water electrolysis

Anion-exchange membrane water electrolysis (AEMWE) represents a promising and cost-effective electrochemical energy conversion system for green hydrogen production owing to its utilization of earth-abundant metals for various cell components (catalysts, porous transport layers, bipolar plates) and the zero-gap design. However, the lack of high-performance anion-exchange membranes (AEMs) has hampered the advancement of AEMWE technology. Here, by using colon coupling and click reactions, the ether-free polyphenylene-based AEMs (QPPBTF-TMA-w) with flexible side-chains containing triazole linkers. The QPPBTF-TMA-w membranes stand out for their lower activation energy for hydroxide conduction which is attributed to the well-structured ion-conducting channels via distinct phase separation facilitated by the triazole linker, which optimizes hydrophilicity and ensures efficient ion transport within the membrane. In addition, the QPPBTF-TMA-w membranes exhibit unique anisotropic swelling and ion-conduction behaviors, such as lower in-plane swelling and higher through-plane conductivity, which are advantageous for practical cell applications. Therefore, despite having a modest ion exchange capacity (IEC) value of 2.0, the QPPBTF-TMA-w membrane delivers high-performance in anion-exchange membrane water electrolysis (AEMWE), achieving 6.4 A/cm2 at 2.0 V at 70 °C using a 1.0 M KOH solution.

Synthesis and Characterization of Enhanced Proton-Conducting Nafion<sup>® </sup>117- Silica Composite Membranes for Fuel Cell Applications

Nafion®/silica nanocomposite membranes were prepared by impregnation method from Nafion® 117 and sol-gel pre-synthesized n-octadecyl-trimethoxy silane (C18TMS) coated silica nanoparticles. The scanning electron microscope (SEM) of pristine silica particles displayed monodispersed nanospheres with diameters ranging from 150-350 nm; while Brunauer-Emmett-Teller (BET) analysis presented 760 m2/g BET surface area, a micropore-mesopore bimodal distribution of micropore systems with respective pore volume at 14.6 Å and 17.0 Å (2.01 x 10-3 cm3/g.Å), as well as the prolific mesopores centered at 29.5 Å (5.64 x 10-2 cm3/g.Å). Characterization of Nafion® 117 based membranes on SEM, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and x-ray diffraction (XRD), and tensile stress exhibited varying surface morphology with silica loadings, structural interaction between membrane support and the ion exchanger, thermal stabilities (up to 330 °C), crystalline nature, and reasonable mechanical stability of nanocomposite membranes. The maximum water uptake (44.8 %) and proton conductivity of (1.14 x10-2 S/cm) were obtained on low Nafion®/SiO2 (5%) loaded membrane. While both composite membranes displayed the improved reduction in methanol permeability, 2.43x10-07 cm2/s at 80 °C was obtained with high Nafion®/SiO2 (10%) loading. Improved water uptake and proton conductivity substantiate the high ion exchange capacity (IEC) of 1.81 meq.g-1 when compared to IEC of 0.93 meq.g-1 [pristine Nafion®] and 1.46 meq.g-1 [Nafion®/SiO2 (10%)]. The increase in IEC value may be due to the high acid functionalization of additional sulfonic acid groups surrounded by hydrophilic segments of nanosilica, which improves the properties of the membrane. The high proton conductivity coupled with great water retention capabilities indicated that the Nafion®/SiO2 nanocomposite membranes could be utilized as proton exchange membranes for medium temperature methanol fuel cells. Keywords: Fuel cells; nanocomposite membrane; SiO2 nanofillers; methanol permeability; ion exchange capacity

Sulfonated Cobalt Metal-Organic Framework Embedded Mixed Matrix Membrane towards Fuel-Cell Applications.

New strategies for enhancement of the fuel-cell performance of a poly(2,5-benzimidazole) (ABPBI) membrane loaded with a functionalized cobalt-based metal-organic framework (MOF) for H2-O2 fuel cells. ABPBI was prepared using the polycondensation method, and various proportions of sulfonated cobalt MOF (sCo-MOF) were incorporated into ABPBI to fabricate a proton-exchange membrane (PEM). Later, the fabricated membranes were soaked in 1 M sulfuric acid to produce sulfonated PEMs. The developed composite membranes had increased proton conductivity, tensile strength, physicochemical properties, and fuel-cell performance compared to the sulfonated ABPBI (sABPBI) membrane. A membrane embedded with 4 wt % sCo-MOF shows higher water uptake and ion-exchange capacity values of 23.25% and 2.89 mequiv g-1, respectively. The membrane electrode assemblies were fabricated to perform unit-cell tests for both sABPBI and 4 wt % sCo-MOF/sABPBI membranes. The 4 wt % sCo-MOF-loaded sABPBI membrane demonstrated good unit-cell performance in the fuel-cell test, with a power density of 415.8 mW cm-2 at 80 °C, superior to the pristine sABPBI membrane's power density of 178.6 mW cm-2.

Novel Fluoroboric Acid Additive for Blend Membrane to be Used in PEM Fuel Cell, Characterization Studies, and Performance Test

This study focuses on developing an alternative membrane for PEMFC due to the disadvantages of using Nafion. Fluoroboric acid (FBA) was used as an additive material to SPEEK-PVA blend membranes at different weight ratios (1%, 5%, 7.5%, 10%, and 12.5%), and a synthesis procedure was carried out with the solution-casting. Thermal crosslinking was performed with all membranes. Utilizing FBA, with its highly electronegative fluorine groups, is a novel approach expected to enhance proton conductivity. The structural, morphological, and thermal properties of the synthesized membranes were determined by FTIR, XRD, SEM, TGA-DTG, and DSC. Water uptake capacity (WUC), swelling property, area change, dynamic mechanical analysis, ion exchange capacity (IEC), AC impedance analysis, hydrolytic stability, and oxidative stability analyses were performed for fuel cell applications. Although FBA does not have a crystal structure, the synergy it created with the SPEEK-PVA membrane increased the crystallinity of the membrane and, accordingly, glass transition temperature. SEM images of membranes at a ratio above 7.5% show that agglomerations occur in the structure and this is supported by other analyses. It was determined that the membrane composition with the highest WUC (16.44%), IEC (1.55 meq/g), and proton conductivity (0.57 S/cm) values contained 7.5% FBA from the characterization studies, and a single-cell performance test was actualized with this. 418 mA/cm2 current density and 250.8 mW/cm2 power density were obtained at 0.6 V cell potential, with the membrane containing 7.5% FBA. This study shows that the synthesized membrane, especially the FBA, is a promising option for PEMFC application.Graphical

Effect of Plasma pretreatment and Graphene oxide ratios on the transport properties of PVA/PVP membranes for fuel cells

In this study, a novel proton-conducting polymer electrolyte membrane based on a mixture of polyvinyl alcohol (PVA)/polyvinyl pyrrolidone (PVP) (1:1) mixed with different ratios of graphene oxide (GO) and plasma-treated was successfully synthesized. Dielectric barrier dielectric (DBD) plasma was used to treat the prepared samples at various dose rates (2, 4, 6, 7, 8, and 9 min) and at fixed power input (2 kV, 50 kHz). The treated samples (PVA/PVP:GO wt%) were soaked in a solution of styrene and tetrahydrofuran (70:30 wt%) with 5 × 10−3 g of benzoyl peroxide as an initiator in an oven at 60 °C for 12 h and then sulfonated to create protonic membranes (PVA/PVP-g-PSSA:GO). The impacts of graphene oxide (GO) on the physical, chemical, and electrochemical properties of plasma-treated PVA/PVP-g-PSSA:x wt% GO membranes (x = 0, 0.1, 0.2, and 0.3) were investigated using different techniques. SEM results showed a better dispersion of nanocomposite-prepared membranes; whereas the AFM results showed an increase in total roughness with increasing the content of GO. FTIR spectra provide more information about the structural variation arising from the grafting and sulfonation processes to confirm their occurrence. The X-ray diffraction pattern showed that the PVA/PVP-g-PSSA:x wt% GO composite is semi-crystalline. As the level of GO mixing rises, the crystallinity of the mixes decreases. According to the TGA curve, the PVA/PVP-g-PSSA:x wt% GO membranes are chemically stable up to 180 °C which is suitable for proton exchange membrane fuel cells. Water uptake (WU) was also measured and found to decrease from 87.6 to 63.3% at equilibrium with increasing GO content. Ion exchange capacity (IEC) was calculated, and the maximum IEC value was 1.91 meq/g for the PVA/PVP-g-PSSA: 0.3 wt% GO composite membrane. At room temperature, the maximum proton conductivity was 98.9 mS/cm for PVA/PVP-g-PSSA: 0.3 wt% GO membrane. In addition, the same sample recorded a methanol permeability of 1.03 × 10−7 cm2/s, which is much less than that of Nafion NR-212 (1.63 × 10−6 cm2/s). These results imply potential applications for modified polyelectrolytic membranes in fuel cell technology.

Oligo (ethylene glycol)-grafted poly(terphenyl indole piperidinium) with high water diffusivity for anion exchange membrane fuel cells

The water diffusivity of polymeric anion exchange membranes (AEMs) plays a critical role in determining the AEM fuel cells (AEMFCs) performance because it generates an imbalance in the amount of water at the anode and cathode. However, the correlation between water diffusivity and the chemical structure of AEMs remains unclear. This study focuses on a series of oligo(ethylene glycol) (OEG) functionalized poly(arylene indole piperidinium) AEMs, in which OEG grafts are directly attached onto the polymer backbones. The polar and flexible OEG side chains afford a microphase-separated morphology, close polymer-chain packing, and extra sites for water–ion transport, resulting in high ion-exchange-capacity (IEC)-normalized conductivity, improved water diffusivity, and dimensional stability. Moreover, these side chains provide excellent ex-situ stability in a 1 M NaOH solution (80 °C) for 1080 h, surpassing the stability of its alkyl side chain counterpart (PITP-C10Q85) by a significant margin. The resultant PITP-OEG-85 with the highest water diffusivity exhibits a highest peak power density of 1.23 W cm−2 at 80 °C despite its low IEC value and conductivity. In-situ durability tests of this membrane at 0.2 A cm−2 for 24 h revealed the degradation of piperidinium under harsh conditions (70 % anode relative humidity at 60 °C). This work opens a new avenue for designing highly conductive and alkali-stable AEM materials with high water diffusivity to realize high-performance AEMFCs.

Development of durable anion-exchange membranes using polyfluorene–based electrolytes and pore-filling method for direct formate fuel cells

Highly durable ether-linkage-free polyfluorene–based electrolytes with different ion exchange capacities (IECs) were synthesized, followed by the preparation and evaluation of cast and pore-filling (PF) membranes as anion exchange membranes (AEMs). The performance of these membranes was tested in direct formate fuel cells (DFFCs). The membrane properties, including formate permeability, were investigated to clarify the relationship between membrane performance and the performance of DFFCs. The formate permeability of the membrane was drastically affected by the existence of OH− anion, as OH− ions induce larger membrane swelling. In addition, the PF method was more effective in reducing the formate permeation than the cast membranes. The PF membrane using the polyelectrolyte with a low IEC value showed 20-fold lower formate permeability compared to that of the original cast membrane, leading to a higher improvement in open-circuit voltage (OCV), from 0.55 to 0.95 V in DFFCs. For the first time, a quantitative correlation between the formate permeability of AEMs and OCV values in DFFCs was established. From this correlation, formate permeation less than 0.03 mol L−1 h−1 is necessary to keep high OCV value. Using the developed membrane, we also demonstrated the high stability of DFFC at 80 °C for 5 days.

In-Situ Analysis of Electrodes Using Fine-Tuned Poly(Terphenyl Piperidinium) Ionomers in Anion Exchange Membrane Fuel Cells

In the field of low temperature polymer electrolyte fuel cells, anion exchange membrane fuel cells (AEMFCs) have been considered a promising alternative by circumventing the obstacles to commercialization faced by the established PEMFC technology. The application of platinum group metal-free catalysts for the oxygen reduction reaction, the potential to utilize cheaper and more sustainable polymers than the industry benchmark Nafion®, and the generally less corrosive alkaline operation conditions, have all been identified as inherent advantages of the AEMFC technology, potentially enabling more cost-effective and environmental-friendly mass production of AEMFC system.The first major challenge in developing AEMFC systems was the lack of stable and conductive anion exchange polymers to be used as membrane and ionomer materials. This challenge was at least partly overcome by the successful development of a variety of next-generation polymers. Among those, poly(arylene piperidinium) show great potential through the combination an ether-free aromatic backbone for increased mechanical stability with a piperidinium-based cationic groups displaying excellent resistance to hydroxide attack in highly alkaline environment [1]. Furthermore, the crucial parameters ion exchange capacity (IEC), water uptake and dimensional swelling can be finely controlled via copolymerization and partial substitution of the cationic functional group in the repeating unit [2].In a previous study using a series of poly(terphenyl piperidinium) membranes with different IECs, we established the importance of these three parameters, in particular for the ionomer used in the catalyst layer of the electrode [3]. Furthermore, it was established that water balance of AEMFC systems proved to be one of the greatest challenges in reaching and maintaining high cell performance. The asymmetrical nature of the simultaneous electrochemical production and consumption of water at the anode and cathode, respectively, necessitates fine-tuning the ionomer properties, as well as selecting operational parameters for each electrode individually in order to strike an optimal water balance [4].In this study, we expand on our previous work by analyzing a matrix of electrode combination based on three poly(terphenyl piperidinium)ionomers with different IEC values. Furthermore, we complemented our analysis by evaluating the effects of substituting a fraction of regular dissolvable ionomer with insoluble non-conformal particles of cross-linked poly(terphenyl piperidinium). The beneficial effects of insoluble non-conformal ionomer particles in the catalyst layer has been previously shown by Varcoe and coworkers utilizing radion-grafted anion exchange membranes [5], and by Holdcroft and coworkers utilizing phenylated poly(phenylene) ionomers for PEMFCs [6].Different electrode combinations were evaluated while varying operational parameters such as gas flow rates, gas relative humidities and back pressure. The recording of observed cell performances were complemented by in-situ analysis of in-let/out-let gas relative humidities, H2/O2 electrochemical impedance spectroscopy for kinetic analysis and information on ohmic losses, H2/Ar electrochemical impedance spectroscopy to measure ionic conductivity, cyclic voltammetry to measure electrochemically active surface area as well as ex-situ characterization of the electrodes before/after the test run.The study was carried out with the aim to establish a correlation between the properties of individually tuned ionomers and operational parameters, and to investigate reasons for performance losses due to mass transport limitations, drop in ionomer conductivity, loss of active area, and decreased kinetics caused by phenyl adsorption.Finally, we demonstrate how the application of individually optimized electrodes using fine-tuned poly(terphenyl piperidinium) based ionomers in conjunction with suitable operating conditions will lead to a drastic increase in fuel cell performance compared to symmetrical non-optimized electrodes.A selection of experimental data is shown in Figure 1.[1] J. S. Olsson, T. H. Pham, P. Jannasch, Adv. Funct. Mater. 2017, 28, 1702758.[2] J. S. Olsson, T. H. Pham, P. Jannasch, Tuning poly(arylene piperidinium) anion-exchange membranes by copolymerization, partial quaternization and crosslinking, J. Membrane Sci., 2019, 578, 183-195.[3] T. Novalin, D. Pan, G. Lindbergh, C. Lagergren, P. Jannasch, R.W. Lindström, Electrochemical performance of poly(arylene piperidinium) membranes and ionomers in anion exchange membrane fuel cells, J. Power Sources, 2021, 507, 230287. [4] D. P. Leonard, S. Maurya , E. J. Park , S. Noh , C. Bae , E. D. Baca , C. Fujimoto and Y. S. Kim , J. Mater. Chem. A, 2020, 8 , 14135-14144.[5] L. Q. Wang , J. J. Brink , Y. Liu , A. M. Herring , J. Ponce-Gonzalez , D. K. Whelligan and J. R. Varcoe, Energy Environ. Sci., 2017, 10 , 2154-2167.[6] E. Balogun, S. Cassegrain, P. Mardle, M. Adamski, T. Saatkamp, and S. Holdcroft, ACS Energy Lett. 2022, 7, 2070-2078. Figure 1

High Durability of Pemion® Proton Exchange Membranes in Cross-Pressure Accelerated Mechanical Stress Tests

Polymer electrolyte membrane fuel cells (PEMFC) are the dominant technology for hydrogen-powered fuel cell electric vehicles in clean transportation systems. To be suitable for commercialization and applicability in real-world use-cases, light and heavy-duty fuel cell vehicles require lifetimes of over 8,000 and 30,000 hours, respectively [1]. Hence, enhancing the durability of all fuel cell components, particularly the proton exchange membrane (PEM), is of great importance.Recently, fuel cell membranes based on hydrocarbon (HC) chemistries have become increasingly common in the literature [2]. Materials with polyaromatic backbones, tunable electrochemical properties, and low reactant permeability are increasingly seen as potential alternatives to incumbent perfluorosulfonic acid (PFSA) materials [2]. Additionally, as restrictions on the use of fluorinated materials in various industries continue to grow, the importance of HC chemistries will as well. Sulfo-phenylated polyphenylenes (sPPPs) are a particular class of HC materials that show promise [3]. However, the phase separation between hydrophilic and hydrophobic domains within sPPPs may not be as discrete as in PFSAs [3], requiring higher ion exchange capacity (IEC) values than PFSAs to achieve similar protonic conductivity. High IEC typically results in greater material hydrophilicity, which can render membranes dimensionally unstable in a fuel cell [4].State-of-the-art commercial PEMs are now manufactured as thin films (≤ 18 µm), offering small ohmic loss and therefore high fuel cell performance. To improve dimensional stability and eliminate the risks of electrical shorting, PEMs are commonly mechanically reinforced using a porous, inert, and non-ionic substrate, such as expanded polytetrafluoroethylene (ePTFE). In a work by Miyake et al. [5], sulfonated polyphenylene-based ionomer membranes with flexible polyethylene mechanical reinforcement were prepared and the results indicated promising mechanical properties and improved longevity in RH cycling tests. However, there is still a lack of data about the fatigue durability of HC membranes in the literature, and evaluating and comparing the mechanical durability of numerous PEMs with a mechanical reinforcement layer in a traditional wet-dry cycling accelerated stress test would be a time-consuming and thus costly process [6].In our previous work, [7] we combined constant pressure differential across an ePTFE-reinforced perfluorosulfonic acid (PFSA) ionomer membrane with in-situ RH cycles (ΔP-AMST) to simulate the actual mechanical stresses in the fuel cell environment, while accelerating the durability testing for reinforced PEMs. In this study, ΔP-AMST is used to benchmark the fatigue lifetime curves for Pemion® membranes and compare it with a commercial reinforced PFSA-based PEM. The test temperature was set to 90 °C, and dry and wet (90% RH) phases were 60s and 30s, respectively. The hardware and semi-MEA specifications used for the test are shown in Figure 1a-c. A semitransparent polycarbonate spacer plate with 20 mm thickness and a circular aperture (25.4 mm) in the middle was used to allow free expansion of the membrane (Figure 1d). The cathode side was pressurized to create a cross pressure between the two sides and intensify the stress on the membrane during the RH cycling process. The ultimate failure of the membrane is shown in Figure 1e. The radial stress at the center of the deformed membrane is estimated by Hencky’s solution, as reported in our previous work [7]. Figure 1f demonstrates the estimated nominal stress on the membranes as a function of their lifetimes in terms of RH cycles. According to the fatigue S-N curves, reinforced Pemion® membranes afford longer lifetime than incumbent PFSA materials if the membrane edges are well protected. In addition, the impact of IEC on the fatigue durability of Pemion® membranes is investigated and the results are evaluated against stress of dehydration and dynamic mechanical analysis measurements. Acknowledgements This project was financially supported by Natural Sciences and Engineering Research Council of Canada (NSERC), Ionomr Innovations Inc, Canada Foundation for Innovation (CFI), British Columbia Knowledge Development Fund (BCKDF), Western Economic Diversification Canada (WD), and Canada Research Chairs (CRC).

Fabrication of dense anion exchange membranes by filling polymer matrix into quaternized branched polyethyleneimine @cellulose aerogel through in-situ polymerization

In order to construct interconnected three-dimensional ion transport structures within anion exchange membranes (AEMs), we proposed the idea of preparing AEMs by filling the aerogel three-dimensional network skeleton by in-situ polymerization. First, quaternized branched polyethyleneimine (QBPEI) with a large number of quaternary ammonium groups was cross-linked with cellulose to construct an aerogel with a three-dimensional network. Then, poly(4-vinylbenzyl chloride) (PVBC) was filled into the aerogel network through in-situ polymerization. Finally, dense AEMs with internal three-dimensional ion transport networks were prepared by hot pressing PVBC/QBPEI@cellulose. The prepared AEMs have low ion exchange capacity (IEC) values and high ionic conductivities, with the membrane with the best overall performance (IEC value of 1.58 meq./g) having a maximum hydroxide conductivity of 38.88 mS/cm at 80 °C. In addition, the optimized membrane has good chemical and dimensional stability, and the maximum power density of the fuel cell assembled based on it is 46.32 mW/cm2. Although the performance of the prepared composite membranes needs to be further improved due to the preparation process, the design idea in this work provides a feasible solution for the construction of continuous ion fast transport channels in AEMs.

Synthesis and fabrication of Cu-trimesic acid MOF anchored sulfonated Poly(2,5-benzimidazole) membranes for PEMFC applications

Porous metal–organic frameworks (MOFs) have started to gain attention because of their high crystallinity, porosity and structural designability, and they can facilitate proton conduction, but the poor membrane forming ability of MOFs limits their application. In this work, composite membranes based on poly (2,5-benzimidazole) (ABPBI) are focused, and the polymer ABPBI was synthesized from its monomer by solution polycondensation method using polyphosphoric acid (PPA) as solvent. Copper-trimesic acid (Cu-TMA) based metal-organic framework (MOF) was prepared by solvothermal synthesis. Varying ratios of MOF were incorporated into the ABPBI polymer matrix to develop a polymer electrolyte membrane (PEM) by solvent casting technique. Sulfonated composites were obtained by immersing the membranes in 20% sulfuric acid and the membranes were used to characterize the crystallographic structure and surface morphology by XRD and SEM. The membrane's mechanical, thermal and physicochemical properties, like tensile strength, thermogravimetric analysis, contact angle, water uptake, swelling ratio, ion exchange capacity, oxidative stability and proton conductivity, have also been evaluated. The 3 wt% Cu-TMA loaded membrane exhibited the highest proton conductivity of 0.039 S cm−1 at 80 °C, whereas the neat sABPBI showed 0.024 S cm−1. Cu-TMA/sABPBI based PEMs are good candidates for polymer electrolyte membrane fuel cells, as shown by their water uptake and ion exchange capacity values of 21.58% and 1.66 meq g−1.

Design and Development of Copper Trimesic Acid Anchored sPEEK/Polyimide Composite Membranes for Fuel Cell Applications

AbstractElectrolyte membranes play a critical role as their properties directly influences the performance of fuel cell. A copper‐based metal organic framework (MOF) anchored polymeric blend membrane was developed for fuel cell application. Cu‐MOF serves as an excellent filler material due to its small size, high degree of crystallinity and surface area. Through XRD analysis well defined crystallite sites was evidenced and the average crystallite size measured ∼ 0.3 Å. The acidic functional group in MOF interacts with sulfonic acid (−SO3H) group in sulfonated polyetheretherketone (sPEEK) matrix which further improves proton conduction via. hydrogen bonding interaction. With the as‐prepared sPEEK as the matrix; polyimide (PI) was blended to improve its processibility and thermal stability. Cu‐MOF loaded composite membranes (X wt.% Cu‐MOF‐sPEEK/PI) were prepared and characterized. To assess the suitability of the developed membranes for proton exchange membrane fuel cell (PEMFC) applications, ion exchange capacity (IEC), water uptake and proton conductivity was measured. 3 wt.% Cu‐MOF‐2‐sPEEK/PI membrane displayed an IEC value of 2.35 meq g−1 with a water uptake of 38.18 % and proton conductivity of 0.0711 S cm−1. Overall, the experimental results of the prepared membranes revealed that they act as an efficient proton exchange membrane (PEM) for PEMFCs.

Multi-Block Copolymer Membranes Consisting of Sulfonated Poly(p-phenylene) and Naphthalene Containing Poly(arylene Ether Ketone) for Proton Exchange Membrane Water Electrolysis

Glassy hydrocarbon-based membranes are being researched as a replacement for perfluorosulfonic acid (PFSA) membranes in proton exchange membrane water electrolysis (PEMWE). Here, naphthalene containing Poly(arylene Ether Ketone) was introduced into the Poly(p-phenylene)-based multi-block copolymers through Ni(0)-catalyzed coupling reaction to enhance π-π interactions of the naphthalene units. It is discovered that there is an optimum input ratio of the hydrophilic monomer and NBP oligomer for the multi-block copolymers with high ion exchange capacity (IEC) and polymerization yield. With the optimum input ratio, the naphthalene containing copolymer exhibits good hydrogen gas barrier property, chemical stability, and mechanical toughness, even with its high IEC value over 2.4 meq g-1. The membrane shows 3.6 times higher proton selectivity to hydrogen gas than Nafion 212. The PEMWE single cells using the membrane performed better (5.5 A cm-2) than Nafion 212 (4.75 A cm-2) at 1.9 V and 80 °C. These findings suggest that naphthalene containing copolymer membranes are a promising replacement for PFSA membranes in PEMWE.

Lead(II) sulfide micro‐crystals doped graphene nanosheets dispersed thermoplastic and multifunctional poly(benzoxazines) cured epoxy resin nanocomposites for medium temperature proton exchange membrane fuel cell applications

AbstractThe amphiphilic polybenzoxazines‐co‐epoxy membrane (POPBOs/PTGP) was created by thermally cross‐linking the multi‐functional octylamine‐based benzoxazine monomer (OPBOs) with synthesized 1,3,5‐tris(oxiran‐2‐yl methoxy)benzene epoxy monomer (TGP). Fourier transform infrared spectroscopy, powder x‐ray diffraction, scanning electron microscopy, and high‐resolution transmission electron microscopy were used to investigate the functionality, crystallinity, and morphology of microcrystal lead(II) sulfide (PbS)/graphene nanosheets (mPbS/GNs). The bare POPBOs/PTGP and different amounts of mPbS/GNs dispersed polymer nanocomposites (PNCs) were obtained from the thermal curing process. Following that, these PNCs were used in medium‐temperature proton exchange membrane fuel cells. The water uptake, ion exchange capacity (IEC), swelling ratio, oxidative stability, and proton conductivity (PC) of bare and loaded mPbS/GNs hybrid nanostructures on POPBOs/PTGP composite membranes were determined. 3 wt% mPbS/GNs distributed with POPBOs/PTGP PNCs exhibit the highest IEC value of 3.61 mmol/g−1 at room temperature, and a PC value of around 6.33 × 10−2 S/cm−1 at 120°C was obtained for the POPBOs/PTGP PNCs. In addition, the single‐cell electrode analysis of the 3 wt% mPbS/GNs‐filled POPBOs/PTGP amphiphilic PNCs showed excellent peak power density and open circuit voltage values of 0.897 W cm−2 and 0.97 V at 120°C.

Synthesis and characterization of sulfonated polytriazoles utilizing 1,4‐bis(4‐azido‐2‐(trifluoromethyl)phenoxy)benzene for the proton exchange membrane applications

AbstractThe aromatic hydrocarbon‐based sulfonated polytriazoles have a reputation as a high‐performing polymer because of their excellent properties. This work demonstrates the synthesis of a new semi‐fluorinated diazide monomer, that is, 1,4‐bis(4‐azido‐2‐(trifluoromethyl)phenoxy)benzene (BATFB), and exploiting this compound a series of aromatic hydrocarbon‐based semi‐fluorinated sulfonated polytriazoles (BABPSSH‐60, −70, −80, −90) was synthesized utilizing the Cu(I)‐induced “click” cycloaddition polymerization reaction along with the sulfonated diazide monomer, 4,4′‐diazido‐2,2′‐stilbenesulfonic acid disodium salt tetrahydrate (DASSA) and the terminal dialkyne monomer, 4,4′‐(propane‐2,2′‐diyl)bis((prop‐2‐ynyloxy)benzene) (BPAAL). The structural analysis of those copolymers was completed by the FTIR and the NMR (1H and 13C) spectroscopic methods. Further, the degree of sulfonation (DS) and the ion exchange capacity (IEC) values of the copolymers were confirmed using the 1H NMR spectrums. They are readily soluble in respective solvents, and a light yellowish membrane was obtained using the solution casting procedure. These membranes demonstrated admissible mechanical and thermal stabilities, balanced water absorption properties, and reasonable chemical stability. The surface phase (SAXS, AFM) and bulk phase (TEM) morphological analysis proved the well‐separated phase morphology. The BABPSSH‐90 displayed a proton conductivity of 104 mS cm−1 at 90.