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1
Cho, Hyeongrae, Henning Krieg, and Jochen Kerres. "Performances of Anion-Exchange Blend Membranes on Vanadium Redox Flow Batteries." Membranes 9, no. 2 (February 17, 2019): 31. http://dx.doi.org/10.3390/membranes9020031.
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Anion exchange blend membranes (AEBMs) were prepared for use in Vanadium Redox Flow Batteries (VRFBs). These AEBMs consisted of 3 polymer components. Firstly, PBI-OO (nonfluorinated PBI) or F6-PBI (partially fluorinated PBI) were used as a matrix polymer. The second polymer, a bromomethylated PPO, was quaternized with 1,2,4,5-tetramethylimidazole (TMIm) which provided the anion exchange sites. Thirdly, a partially fluorinated polyether or a non-fluorinated poly (ether sulfone) was used as an ionical cross-linker. While the AEBMs were prepared with different combinations of the blend polymers, the same weight ratios of the three components were used. The AEBMs showed similar membrane properties such as ion exchange capacity, dimensional stability and thermal stability. For the VRFB application, comparable or better energy efficiencies were obtained when using the AEBMs compared to the commercial membranes included in this study, that is, Nafion (cation exchange membrane) and FAP 450 (anion exchange membrane). One of the blend membranes showed no capacity decay during a charge-discharge cycles test for 550 cycles run at 40 mA/cm2 indicating superior performance compared to the commercial membranes tested.
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Kuppusamy, Hari Gopi, Prabhakaran Dhanasekaran, Niluroutu Nagaraju, Maniprakundil Neeshma, Baskaran Mohan Dass, Vishal M. Dhavale, Sreekuttan M. Unni, and Santoshkumar D. Bhat. "Anion Exchange Membranes for Alkaline Polymer Electrolyte Fuel Cells—A Concise Review." Materials 15, no. 16 (August 15, 2022): 5601. http://dx.doi.org/10.3390/ma15165601.
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Solid anion exchange membrane (AEM) electrolytes are an essential commodity considering their importance as separators in alkaline polymer electrolyte fuel cells (APEFC). Mechanical and thermal stability are distinguished by polymer matrix characteristics, whereas anion exchange capacity, transport number, and conductivities are governed by the anionic group. The physico-chemical stability is regulated mostly by the polymer matrix and, to a lesser extent, the cationic head framework. The quaternary ammonium (QA), phosphonium, guanidinium, benzimidazolium, pyrrolidinium, and spirocyclic cation-based AEMs are widely studied in the literature. In addition, ion solvating blends, hybrids, and interpenetrating networks still hold prominence in terms of membrane stability. To realize and enhance the performance of an alkaline polymer electrolyte fuel cell (APEFC), it is also necessary to understand the transport processes for the hydroxyl (OH−) ion in anion exchange membranes. In the present review, the radiation grafting of the monomer and chemical modification to introduce cationic charges/moiety are emphasized. In follow-up, the recent advances in the synthesis of anion exchange membranes from poly(phenylene oxide) via chloromethylation and quaternization, and from aliphatic polymers such as poly(vinyl alcohol) and chitosan via direct quaternization are highlighted. Overall, this review concisely provides an in-depth analysis of recent advances in anion exchange membrane (AEM) and its viability in APEFC.
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Lee, Seunghyun, Hyejin Lee, Tae-Hyun Yang, Byungchan Bae, Nguyen Anh Thu Tran, Younghyun Cho, Namgee Jung, and Dongwon Shin. "Quaternary Ammonium-Bearing Perfluorinated Polymers for Anion Exchange Membrane Applications." Membranes 10, no. 11 (October 26, 2020): 306. http://dx.doi.org/10.3390/membranes10110306.
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Perfluorinated polymers are widely used in polymer electrolyte membranes because of their excellent ion conductivity, which are attributed to the well-defined morphologies resulting from their extremely hydrophobic main-chains and flexible hydrophilic side-chains. Perfluorinated polymers containing quaternary ammonium groups were prepared from Nafion- and Aquivion-based sulfonyl fluoride precursors by the Menshutkin reaction to give anion exchange membranes. Perfluorinated polymers tend to exhibit poor solubility in organic solvents; however, clear polymer dispersions and transparent membranes were successfully prepared using N-methyl-2-pyrrolidone at high temperatures and pressures. Both perfluorinated polymer-based membranes exhibited distinct hydrophilic-hydrophobic phase-separated morphologies, resulting in high ion conductivity despite their low ion exchange capacities and limited water uptake properties. Moreover, it was found that the capacitive deionization performances and stabilities of the perfluorinated polymer membranes were superior to those of the commercial Fumatech membrane.
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Pintauro, Peter N. "(Invited) Monopolar and Bipolar Membranes Based on Nanofiber Electrospinning." ECS Meeting Abstracts MA2023-02, no. 39 (December 22, 2023): 1893. http://dx.doi.org/10.1149/ma2023-02391893mtgabs.
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Cation-exchange, anion-exchange, and bipolar membranes play crucial roles in a variety of electrochemical processes and devices, including chloralkali cells, electrodialysis separations for water purification, proton-exchange membrane and hydroxide-exchange membrane (alkaline) fuel cells, redox flow batteries, and processes for direct air capture of CO2. The incorporation of polymeric nanofibers into such membranes provides an attractive and tunable method of creating materials with new nano-morphologies and highly desirable properties. The impregnation of an ionomer solution into a pre-formed nonwoven porous mat of electrospun polymer fibers is a well-known method of making reinforced proton-exchange membranes. The use of simultaneous dual-fiber electrospinning or the electrospinning of polymer blends can be used to intermix/incorporate/co-locate dissimilar and incompatible polymers on the nanoscale. Although less studied in the literature, these methods offer many interesting possibilities for new membrane structures with targeted and unique transport and mechanical properties. In this review talk, the use of dual fiber and blended polymer fiber electrospinning for membrane fabrication will be presented for the following: (1) Nanofiber reinforced cation (proton) exchange membranes, (2) Electrospun NafionTM/PVDF dual fiber and single-fiber membranes for H2/Br2 redox flow batteries, (3) Composite anion exchange membranes, and (4) Bipolar membranes with a 3D nanofiber junction. Materials and methods for membrane fabrication will be described and the properties of the membranes will be discussed.
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Yang, Zezhou, Ryszard Wycisk, and Peter N. Pintauro. "(Invited) Bipolar Membranes with a 3D Junction of Interlocking Electrospun Fibers." ECS Meeting Abstracts MA2022-02, no. 44 (October 9, 2022): 1661. http://dx.doi.org/10.1149/ma2022-02441661mtgabs.
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Bipolar membranes (BPMs), typically laminated layers of anion-exchange and cation-exchange polymers, have the unique capability of splitting water at a potential near 0.83 V. Such membranes are used in electrodialysis membrane separation processes. They also have applications in water electrolyzers, CO2 electrolysis cells, and self-humidifying fuel cells. We report here on recent developments regarding BPMs with a high interfacial area, 3D nanofiber junction. Membranes were prepared by first creating a bipolar junction layer, by the simultaneous electrospinning of anion-exchange and cation-exchange polymers, with the addition of catalyst nanoparticles to facilitate water splitting. Solvent vapor exposure and hot-pressing closed all interfiber pores, to create a dense film of interpenetrating and interlocking nanofibers of positively and negatively charged polymers. In one fabrication method, dense films of solution cast anion and cation-exchange polymers were hot-pressed onto the opposing surfaces of the junction layer to create a tri-layer BPM. Membranes were also fabricated by electrospinning all three layers of the BPM: first spinning anion-exchange fibers, followed by dual fiber spinning with catalyst spraying, and then spinning only cation-exchange fibers. Solvent exposure and hot-pressing closed all interfiber voids. BPMs were made with a junction layer 12-15 mm thick, where the total membrane thickness was 50-80 mm. Membranes were prepared with both hydrocarbon and fluoropolymer ionomers, e.g., sulfonated poly(ether ether ketone) or perfluorosulfonic acid as the cation-exchange polymer and either quaternized poly(phenylene oxide), AEMIONä (an imidazolium-based polymer sold by Ionomr Innovations, Inc.), or PiperION (a poly(aryl piperidinium) from Versogen) as the anion-exchange polymer. A variety of different junction layer catalysts powders were examined, including Al(OH)3 and graphene oxide. Membranes were evaluated in an H-cell for the collection of steady-state current-voltage data and in a flow cell for long-term constant current water splitting (electrolysis) operation, typically with an aqueous Na2SO4 electrolyte. The 3D junction membranes performed exceptionally well: (i) the water splitting potential was low (near the expected value of 0.83 V), (ii) the transmembrane voltage drop was small at high currents (e.g., a voltage drop of 1.1 V up to 1.1 A/cm2), and (iii) the extended bipolar reaction zone for water splitting with interlocking fibers allowed for high current density operation with no evidence of membrane degradation. In this talk, the effect of membrane composition (the type/amount of anion and cation exchange polymers and choice of catalyst) and structure (the thickness of the layers) on short-term and long-term membrane performance will be discussed. Results will be presented for operating the bipolar membrane in water splitting and water generation modes.
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Wu, Wei. "Block copolymers as anion exchange membrane in fuel cells." Applied and Computational Engineering 66, no. 1 (May 29, 2024): 198–203. http://dx.doi.org/10.54254/2755-2721/66/20240951.
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Anion exchange membranes play a crucial part as the primary component of alkaline fuel cells, yet their optimization remains an ongoing endeavor. While research and development efforts have made strides in advancing anion exchange membranes, a pressing need exists to further refine their mechanical properties, ionic conductivity, and chemical stability, especially in comparison to proton exchange membranes. Block copolymers have emerged as promising candidates among the array of materials explored for enhancing anion exchange membranes due to their inherent advantages. These copolymers offer unparalleled flexibility in adjustment and boast superior mechanical properties, making them highly adaptable for modifying anion exchange membranes to meet desired specifications. In order to demonstrate the benefits of block copolymer, this paper primarily summarizes and examines the techniques for varying the material content, investigating composition to identify the block copolymer anion exchanging membrane with exceptional performance characteristics, and contrasting it with the random copolymer, polymer blend, and homopolymer exchange membrane. The results unequivocally demonstrate the efficacy of block copolymers in improving the material structure of exchange membranes by fine-tuning the polymer content. Notably, block copolymers outperform other copolymers in significantly enhancing the performance metrics of anion exchange membranes. In summary, studying block copolymers is a practical way to significantly enhance the performance and functionality of anionic exchange membranes, which will help the alkaline fuel cell industry move toward greater sustainability
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Kerres, Jochen Alfred. "(Invited) Novel Polymer and Membrane Development Strategies for Water Electrolysis." ECS Meeting Abstracts MA2024-01, no. 34 (August 9, 2024): 1741. http://dx.doi.org/10.1149/ma2024-01341741mtgabs.
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Water electrolysis processes play a crucial role in transitioning to a climate-friendly society. They facilitate the integration of renewable energy, offer a clean and versatile energy carrier, decarbonize industries, improve energy storage and grid stability, and support the development of sustainable transportation solutions. As technology advances and economies of scale are realized, electrolysis is expected to play an increasingly significant role in the clean energy landscape, contributing to a more sustainable and resilient future. Various water-splitting electrolysis processes currently exist, including alkaline, solid oxide, proton exchange membrane (PEM), anion exchange (AEM), acidic-alkaline amphoteric, microbial, and photoelectrochemical methods [1]. In our research group, we are actively involved in membrane development for both PEM and AEM water electrolysis. In PEM electrolysis membrane development, our group explores several approaches, such as (a) aromatic main-chain block copolymers[2],(b) acid-base blend membranes using sulfonated and partially fluorinated aromatic polyether, polybenzimidazole, and a PSU-derived basic polymer[2], (c) poly(fluorene)-based sulfonated ionomers, (d) sulfonated and phosphonated poly(pentafluorostyrene) polymers with flexible side groups, and (d) nanophase-separated block copolymers based on phosphonated[3] or sulfonated pentafluorostyrene and octylstyrene. Additionally, we investigate (e) H+-conductive fiber-mat reinforced perfluorosulfonic acid (PFSA) polymers[4]. The development of anion exchange membranes in our research group includes (a) polystyrene-based side chain anion exchange polymers and their blends with polybenzimidazole[5], (b) polynorbornene-based optionally ionically and covalently crosslinked anion exchange polymers and membranes, (c) side chain anion exchange polymers and membranes prepared by polyhydroxyalkylation[6], and (d) anion exchange blend membranes made from polydiallyldimethylammonium salts and polybenzimidazole. This contribution highlights the application of two polymer types in PEM and AEM membrane water electrolysis, respectively: (A) PEM Water Electrolysis (PEMWE): Membranes from PEM types (a) and (b) demonstrated good performance. PEM (a) achieved 2.2 V@6 A/cm2, and PEM (b) reached 2.26 V@6 A/cm2 (compared to Nafion212: 2.26 V@6 A/cm2)[2]. These performances were accomplished with non-optimized membrane-electrode assemblies using Nafion as the electrode ionomer. Further performance improvements are expected with optimized electrodes containing the same ionomers as used in the membrane. (B) AEM Water Electrolysis (AEMWE): Blend membranes from AEM type (a) exhibited excellent alkali stability (no conductivity decrease after 1000 hrs of storage in 1M KOH@85°C) and good AEMWE performance (CuCo anode catalyst, 1M KOH, 70°C, 2 V@3 A/cm2)[5]. Type (c) AEMs were applied to a seawater electrolysis cell at 60°C, achieving a performance of 2 V@1 A/cm2 using completely noble metal-free catalysts in both the anode and cathode[6]. [1] M. F. Ahmad Kamaroddin, N. Sabli, T. A. Tuan Abdullah, S. I. Siajam, L. C. Abdullah, A. Abdul Jalil, A. Ahmad, Membranes 2021, 11. [2] J. Bender, B. Mayerhöfer, P. Trinke, B. Bensmann, R. Hanke-Rauschenbach, K. Krajinovic, S. Thiele, J. Kerres, Polymers 2021, 13. [3] S. Auffarth, M. Wagner, A. Krieger, B. Fritsch, L. Hager, A. Hutzler, T. Böhm, S. Thiele, J. Kerres, ACS Materials Lett. 2023, 5, 2039. [4] M. S. Mu'min, M. Komma, D. Abbas, M. Wagner, A. Krieger, S. Thiele, T. Böhm, J. Kerres, Journal of Membrane Science 2023, 685, 121915. [5] L. Hager, M. Hegelheimer, J. Stonawski, A. T. S. Freiberg, C. Jaramillo-Hernández, G. Abellán, A. Hutzler, T. Böhm, S. Thiele, J. Kerres, J. Mater. Chem. A 2023. [6] M. L. Frisch, T. N. Thanh, A. Arinchtein, L. Hager, J. Schmidt, S. Brückner, J. Kerres, P. Strasser, ACS Energy Lett. 2023, 8, 2387.
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Samsudin, Asep Muhamad, Sigrid Wolf, Michaela Roschger, and Viktor Hacker. "Poly(vinyl alcohol)-based Anion Exchange Membranes for Alkaline Polymer Electrolyte Fuel Cells." International Journal of Renewable Energy Development 10, no. 3 (February 12, 2021): 435–43. http://dx.doi.org/10.14710/ijred.2021.33168.
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Crosslinked anion exchange membranes (AEMs) made from poly(vinyl alcohol) (PVA) as a backbone polymer and different approaches to functional group introduction were prepared by means of solution casting with thermal and chemical crosslinking. Membrane characterization was performed by SEM, FTIR, and thermogravimetric analyses. The performance of AEMs was evaluated by water uptake, swelling degree, ion exchange capacity, OH- conductivity, and single cell tests. A combination of quaternized ammonium poly(vinyl alcohol) (QPVA) and poly(diallyldimethylammonium chloride) (PDDMAC) showed the highest conductivity, water uptake, and swelling among other functional group sources. The AEM with a combined mass ratio of QPVA and PDDMAC of 1:0.5 (QPV/PDD0.5) has the highest hydroxide conductivity of 54.46 mS cm-1. The single fuel cell tests with QPV/PDD0.5 membrane yield the maximum power density and current density of 8.6 mW cm-2 and 47.6 mA cm-2 at 57 °C. This study demonstrates that PVA-based AEMs have the potential for alkaline direct ethanol fuel cells (ADEFCs) application.
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Shen, Haiyang, Yifei Gong, Wei Chen, Xianbiao Wei, Ping Li, and Congliang Cheng. "Anion Exchange Membrane Based on BPPO/PECH with Net Structure for Acid Recovery via Diffusion Dialysis." International Journal of Molecular Sciences 24, no. 10 (May 11, 2023): 8596. http://dx.doi.org/10.3390/ijms24108596.
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In order to improve the performance of the anion exchange membrane (AEM) used in acid recovery from industrial wastewater, this study adopted a new strategy in which brominated poly (2,6-dimethyl-1,4-phenyleneoxide) (BPPO) and polyepichlorohydrin (PECH) were used as the polymer backbone of the prepared membrane. The new anion exchange membrane with a net structure was formed by quaternizing BPPO/PECH with N,N,N,N-tetramethyl-1,6-hexanediamine (TMHD). The application performance and physicochemical property of the membrane were adjusted by changing the content of PECH. The experimental study found that the prepared anion exchange membrane had good mechanical performance, thermostability, acid resistance and an appropriate water absorption and expansion ratio. The acid dialysis coefficient (UH+) of anion exchange membranes with different contents of PECH and BPPO was 0.0173–0.0262 m/h at 25 °C. The separation factors (S) of the anion exchange membranes were 24.6 to 27.0 at 25 °C. Compared with the commercial BPPO membrane (DF-120B), the prepared membrane had higher values of UH+ and S in this paper. In conclusion, this work indicated that the prepared BPPO/PECH anion exchange membrane had the potential for acid recovery using the DD method.
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Jung, Jiyoon, Young Sang Park, Gwan Hyun Choi, Hyun Jin Park, Cheol-Hee Ahn, Seung Sang Hwang, and Albert S. Lee. "Alkaline-Stable, In Situ Menshutkin Coat and Curable Ammonium Network: Ion-Solvating Membranes for Anion Exchange Membrane Water Electrolyzers." International Journal of Energy Research 2023 (September 30, 2023): 1–12. http://dx.doi.org/10.1155/2023/7416537.
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Anion exchange membranes fabricated through a one-step Menshutkin reaction with down-selected multifunctional alkyl halides and multifunctional tertiary amines within an ion-solvating matrix, poly(ethylene-co-vinyl alcohol), yielded alkaline-stable ammonium network polymers. Due to the vast simplicity in fabrication due to the quaternization/Menshutkin reaction between tertiary amine and alkyl bromides, which does not evolve any by-products that require purification, alkaline-stable membranes were fabricated in one step through facile mixing and curing of alkaline-stable ammonium network forming monomers. Prepared membranes showed controllable ion exchange capacity (IEC), conductivity, and mechanical strength by controlling of poly(ethylene-co-vinyl alcohol) amount which is an ion-solvating polymer. The selection of ammonium network chemical structure allowed for flawless retention of IEC and conductivity under conditions of 70°C, 1M KOH of over 300 h. Anion exchange membrane electrolysis membrane electrode assembly tests with optimized membranes showed a greater performance (1.78 A/cm2 at 2.0 V) and more enhanced water electrolyzer durability than that of commercial anion exchange membrane.
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Cho, Hyeongrae, Vladimir Atanasov, Henning M. Krieg, and Jochen A. Kerres. "Novel Anion Exchange Membrane Based on Poly(Pentafluorostyrene) Substituted with Mercaptotetrazole Pendant Groups and Its Blend with Polybenzimidazole for Vanadium Redox Flow Battery Applications." Polymers 12, no. 4 (April 15, 2020): 915. http://dx.doi.org/10.3390/polym12040915.
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In order to evaluate the performance of the anion exchange membranes in a vanadium redox flow battery, a novel anion exchange polymer was synthesized via a three step process. Firstly, 1-(2-dimethylaminoethyl)-5-mercaptotetrazole was grafted onto poly(pentafluorostyrene) by nucleophilic F/S exchange. Secondly, the tertiary amino groups were quaternized by using iodomethane to provide anion exchange sites. Finally, the synthesized polymer was blended with polybenzimidazole to be applied in vanadium redox flow battery. The blend membranes exhibited better single cell battery performance in terms of efficiencies, open circuit voltage test and charge-discharge cycling test than that of a Nafion 212 membrane. The battery performance results of synthesized blend membranes suggest that those novel anion exchange membranes are promising candidates for vanadium redox flow batteries.
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Vijayakumar, Vijayalekshmi, and Sang Yong Nam. "A Review of Recent Chitosan Anion Exchange Membranes for Polymer Electrolyte Membrane Fuel Cells." Membranes 12, no. 12 (December 14, 2022): 1265. http://dx.doi.org/10.3390/membranes12121265.
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Considering the critical energy challenges and the generation of zero-emission anion exchange membrane (AEM) sources, chitosan-based anion exchange membranes have garnered considerable interest in fuel cell applications owing to their various advantages, including their eco-friendly nature, flexibility for structural modification, and improved mechanical, thermal, and chemical stability. The present mini-review highlights the advancements of chitosan-based biodegradable anion exchange membranes for fuel cell applications published between 2015 and 2022. Key points from the rigorous literature evaluation are: grafting with various counterions in addition to crosslinking contributed good conductivity and chemical as well as mechanical stability to the membranes; use of the interpenetrating network as well as layered structures, blending, and modified nanomaterials facilitated a significant reduction in membrane swelling and long-term alkaline stability. The study gives insightful guidance to the industry about replacing Nafion with a low-cost, environmentally friendly membrane source. It is suggested that more attention be given to exploring chitosan-based anion exchange membranes in consideration of effective strategies that focus on durability, as well as optimization of the operational conditions of fuel cells for large-scale applications.
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Luong, Triet Nguyen Dai, Si Chen, and Patric Jannasch. "Hydroxide Conducting Naphthalene-Containing Polymers and Membranes Via Polyhydroxyalkylations." ECS Meeting Abstracts MA2023-02, no. 39 (December 22, 2023): 1890. http://dx.doi.org/10.1149/ma2023-02391890mtgabs.
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Anion exchange membranes (AEMs) are critical components of alkaline membrane water electrolyzers and fuel cells that are under development today [1,2]. Consequently, there is a strong demand for highly conductive and alkali-stable AEMs. In this context, polyhydroxyalkylation has emerged as one of the most efficient synthetic pathways to chemically resistant polymer backbones for AEMs. In these Friedel-Crafts type polycondensations, an electron-rich aromatic compound reacts with an activated ketone or aldehyde to produce an aryl-ether-free polymer. The desired quaternary ammonium cations are then usually introduced through a Menshutkin reaction [3,4]. In the current work, we have employed naphthalene-based compounds as monomers in polyhydroxyalkylations to prepare a series of high-molecular weight poly(naphthalene alkylene)s with various naphthalene contents. These polymers were then quaternized and cast into AEMs. Here, we will discuss the influence of the naphthalene monomer type and content on AEM properties such as solubility, water uptake, ion conductivity, ionic clustering, thermal and alkaline stability, and also the prospects of using these AEMs in electrochemical systems. References: [1] Chen, N., Wang, H.H., Kim, S.P. et al. Poly(fluorenyl aryl piperidinium) membranes and ionomers for anion exchange membrane fuel cells. Nat. Commun. 12, 2367 (2021). [2] Li, D., Park, E.J., Zhu, W. et al. Highly quaternized polystyrene ionomers for high performance anion exchange membrane water electrolysers. Nat. Energy 5, 378–385 (2020). [3] Olsson, J.S., Pham, T.H., Jannasch, P., Poly(arylene piperidinium) hydroxide ion exchange membranes: synthesis, alkaline stability, and conductivity. Adv. Funct. Mater. 28, 1702758 (2017). [4] Pan, D., Bakvand, P.M., Pham, T.H., Jannasch, P. Improving poly(arylene piperidinium) anion exchange membranes by monomer design. J. Mater. Chem. A 10, 16478–16489 (2022).
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Singh, Siddhant, Flora Tseng, Wei Lu, Jeff Sakamoto, and David G. Kwabi. "Electrochemical Desalination Using a Hybrid Redox-Flow Cell with a Ceramic Ion Conductor." ECS Meeting Abstracts MA2022-02, no. 27 (October 9, 2022): 1058. http://dx.doi.org/10.1149/ma2022-02271058mtgabs.
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Electrochemical desalination is a potentially energy-efficient strategy for distributed, small-scale purification of brackish sources, especially as compared to conventional processes that are reliant on heat or reverse osmosis. One promising subcategory of electrochemical desalination systems features a combination of sodium-intercalating electrodes and polymer-based anion-exchange membranes. Although desalination is technically feasible with this design, polymer-based ion-exchange membranes tend to have imperfect permselectivities and to be susceptible to water crossover between diluate and concentrate streams. These issues result in parasitic losses that increase the energetic cost of desalination. We propose a hybrid flow cell design that features a redox-active electrolyte separated from a solid, anion-converting or anion-intercalating electrode with a solid ceramic ion-exchange membrane. By making use of a dense, ceramic membrane with a far greater selectivity for sodium ion conduction than analogous polymeric ion-exchange membranes, the parasitic issues described above are avoided. We discuss considerations that will impact the relationship among electrode and electrolyte properties, operational parameters (e.g. current density, concentration factor and water recovery percentage) and the energetic cost of desalination.
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Kruczala, Krzysztof, and Dario R. Dekel. "(Invited) Operando EPR Study on Radicals in Anion-Exchange Membrane Fuel Cells." ECS Meeting Abstracts MA2022-02, no. 43 (October 9, 2022): 1623. http://dx.doi.org/10.1149/ma2022-02431623mtgabs.
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In the rapidly developing modern society, there is an urgent need for the wide-ranging availability of advanced and eco-friendly energy sources. One of the possible alternatives is the application of anion exchange membrane fuel cells (AEMFCs) with a catalyst reducing dioxygen efficiently. These promising devices can revolutionize the energy sector since they practically produce no pollution. However, to make them more widely used, several obstacles must be overcome. As a result, vast-ranging investigations focus on improving the properties of conductive polymer membranes [1] and catalysts for the oxygen reduction reaction (ORR) [2]. The durability of the membrane electrode assembly (MEA) is one of the critical requirements for the successful commercialization of anion exchange membrane fuel cells (AEMFCs). Despite significant impacts of nucleophilic degradation on ion-exchange capability and the anionic conductivity of investigated membranes, it is believed to affect only cationic sites of membrane polymers and thus cannot explain the reported loss in the mechanical strength of degraded AEMs. Such a phenomenon might be related to polymer backbone degradation caused by free radicals. This was widely described in the literature in the case of fuel cells using proton-conducting membranes [3] but barely mentioned for AEMFCs [4]. Since the oxidative degradation of hydrocarbon polymers is very well known, we aimed to comprehensively investigate the formation of the short-lived species generated during the operation of AEMFCs as well as stable radicals present in the polymer membranes. We investigated the LDPE-base membranes with Pt black, Pd black, PdAg, and Ag as the ORR catalysts, whereas for HOR the Pt black, Pd black, and NiFe catalysts were used. The in-situ measurements are performed with a micro-AEMFC inserted into a resonator of an electron paramagnetic resonance (EPR) spectrometer, which enables separate monitoring of radicals formed on the anode and cathode sides. The creation of radicals was monitored by the EPR spin trapping technique. In Figure 1 the EPR spectra of DMPO spin adducts trapped during operation of micro-fuel cell placed in EPR spectrometer cavity are presented. In this experiment, the LDPE-base membrane with platinum catalysts on both sides was used. The main detected adducts during the operation of the micro-AEMFC were DMPO-OOH and DMPO-OH on the cathode side and DMPO-H on the anode side. Additionally, we clearly show the formation and presence of stable radicals in AEMs during and after long-term AEMFC operation [5]. Preliminary results suggest that the creation of the short-living radicals during AEMFCs operation is independent of the used membrane. However, the applied catalysts determine the number of detected radicals. The EPR investigations indicate that, in addition to the known chemical degradation mechanisms of the cationic ammonium groups of the membrane, oxidative degradation, including radical reactions, has to be taken into account when the stability of an anion conductive polymer for AEMFCs is investigated. The formation of stable radicals in AEMs was proven for the first time in this study. All short-living radicals formed during the AEMFC operation were fully identified. The presence of radicals in the AEM after AEMFC testing indicates that reactive oxygen species may play a very important role in the degradation mechanism of the anion conducting polymers. Results from this study shed light on the understanding of radical formation and presence in the membranes during AEMFC tests, which in turn may help to solve the challenge of anion exchange membrane stability. Acknowledgments. This work was supported by the Polish National Science Centre (NCN) project OPUS-14, No. 2017/27/B/ST5/01004. References: Dekel, D. R.; Rasin, I. G.; Brandon, S. Predicting Performance Stability of Anion Exchange Membrane Fuel Cells, Power Sources 2019, 420, 118−123. Kostuch A.; Jarczewski S.; Surówka M.K.; Kuśtrowski P.; Sojka Z.; Kruczała K. The joint effect of electrical conductivity and surface oxygen functionalities of carbon supports on the oxygen reduction reaction studied over bare supports and Mn–Co spinel/carbon catalysts in alkaline media, Catal. Technol., 2021, 11, 7578–7591 Łańcucki, L.; Schlick, S.; Danilczuk, M.; Coms, F. D.; Kruczała, K. Sulfonated Poly(Benzoyl Paraphenylene) as a Membrane for PEMFC: Ex Situ and in Situ Experiments of Thermal and Chemical Stability, Polym. Degrad. Stab. 2013, 98 (1), 3. Mustain, W.; Chatenet, M.; Page, M.; Kim, Y. S. Durability Challenges of Anion Exchange Membrane Fuel Cells, Energy Environ. Sci. 2020, 17−19. Wierzbicki, S.; Douglin, J. C.; Kostuch, A.; Dekel D. R.; Kruczała, K. Are Radicals Formed During Anion-Exchange Membrane Fuel Cell Operation?, J. Phys. Chem. Lett., 2020, 11, 7630–7636. Figure 1
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Palanivel, Tamilazhagan, Shankara Kalanur, Vinodh Rajangam, and Bruno Georges Pollet. "Development of a Superior Anion Exchange Membrane with Hyperbranched Polymer for Anion Exchange Membrane Water Electrolysis." ECS Transactions 114, no. 5 (September 27, 2024): 169–77. http://dx.doi.org/10.1149/11405.0169ecst.
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The production of hydrogen using membrane-based electrolyzersposes significant advantages and benefits compared to traditionalelectrolysis methods. Among the electrolyzers, anion exchangemembrane water electrolysis (AEMWE) has emerged as one of thepromising technologies owing to its unique advantages. However,the development of efficient AEMs for water electrolysis presentssignificant challenges, particularly in achieving enhanceddimensional stability and conductivity. In this study, ahyperbranched polyesteramide (HPEA) was synthesized andblended with poly(ether sulfone) (PES) to address the challenges.The resulting QPES-HPEA blend membrane exhibited a lowswelling ratio and high water uptake, which are critical formaintaining dimensional stability and enhancing the hydroxide iontransport efficiency of AEM. The enhanced physical properties andoptimized structure of the membrane make it a promising candidatefor next-generation AEMs in water electrolysis systems.
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Mothupi, Moshito Lethabo, and Phumlani Fortune Msomi. "Quaternized Polyethersulfone (QPES) Membrane with Imidazole Functionalized Graphene Oxide (ImGO) for Alkaline Anion Exchange Fuel Cell Application." Sustainability 15, no. 3 (January 25, 2023): 2209. http://dx.doi.org/10.3390/su15032209.
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Membranes made up of composite materials have shown promising advantages for application in alkaline fuel cell anion exchange membranes. In this study, a general method is employed to improve the overall performance and properties of alkaline anion exchange membranes by making use of polyethersulfone quaternized with imidazolium groups and blended with imidazolium functionalized graphene oxide inorganic filler (ImGO). The inorganic filler blended with the polymer matrix yielded better ionic transport, with 73.2 mS·cm−1 being the highest ion conductivity for the polymer membrane with 0.5% ImGO content, which is higher than that of the QPES parent material. The 0.5% ImGO content also showed better swelling ratio, water uptake, alkaline stability, ion exchange capacity and alkaline stability in comparison to other membranes. Furthermore, it also exhibited 130 mW·cm−2 peak power.
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Xu, Jiahe, Johna Leddy, and Carol Korzeniewski. "Cyclic Voltammetry as a Probe of Selective Ion Transport within Layered, Electrode-Supported Ion-Exchange Membrane Materials." Journal of The Electrochemical Society 169, no. 2 (February 1, 2022): 026520. http://dx.doi.org/10.1149/1945-7111/ac51fd.
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Cyclic voltammetry was applied to investigate the permselective properties of electrode-supported ion-exchange polymer films intended for use in future molecular-scale spectroscopic studies of bipolar membranes. The ability of thin ionomer film assemblies to exclude mobile ions charged similarly to the polymer (co-ions) and accumulate ions charged opposite to the polymer (counterions) was scrutinized through use of the diffusible redox probe molecules [Ru(NH3)6]3+ and [IrCl6]2−. With the anion exchange membrane (AEM) phase supported on a carbon disk electrode, bipolar junctions formed by addition of a cation exchange membrane (CEM) overlayer demonstrated high selectivity toward redox ion extraction and exclusion. For junctions formed using a Fumion® AEM phase and a Nafion® overlayer, [IrCl6]2− ions exchanged into Fumion® prior to Nafion® overcoating remained entrapped and the Fumion® excluded [Ru(NH3)6]3+ ions for durability testing periods of more than 20 h under conditions of interest for eventual in situ spectral measurements. Experiments with the Sustainion® anion exchange ionomer uncovered evidence for [IrCl6]2− ion coordination to pendant imidazolium groups on the polymer. A cyclic voltammetric method for estimation of the effective diffusion coefficient and equilibrium extraction constant for redox active probe ions within inert, uniform density electrode-supported thin films was applied to examine charge transport mechanisms.
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Park, Eun Joo, Christopher Arges, Hui Xu, Chulsung Bae, Cy Fujimoto, Ivana Matanovic, and Yu Seung Kim. "Polymer Design Strategies for Alkaline Membrane Water Electrolysis." ECS Meeting Abstracts MA2023-02, no. 42 (December 22, 2023): 2066. http://dx.doi.org/10.1149/ma2023-02422066mtgabs.
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Water electrolysis is a carbon-free hydrogen production technology, making it a promising candidate to mitigate aggravating climate change. Ion exchange membranes are an essential component of membrane-based water electrolysis, enabling high hydrogen production efficiency through a zero-gap configuration. The recent research efforts to develop anion exchange membranes and electrode ionomers have made significant improvement in durability of alkaline membrane water electrolyzers without sacrificing performance and efficiency. Still, there are several factors related to polymer electrolytes that contribute to the voltage loss for water splitting in the alkaline condition including electrode local pH, the interface between membrane and electrodes, and electrochemical oxidation of ionomers at high potentials. This presentation will provide the state-of-the-art performance of alkaline membrane water electrolyzers with respect to the structure of anion exchange membranes and ionomers. The material design strategies and future directions to develop advanced polymer electrolytes will be discussed for this green hydrogen production technology. Reference: Park, E.J., Arges, C.G., Xu, H., Kim, Y.S. ACS Energy Lett. 2022 , 7, 10, 3447–3457 Motz, A.R., Li, D., Keane, A., Manriquez, L.D., Park, E.J., Maurya, S., Chung, H., Fujimoto, C., Jeon, J., Pagels, M.K., Bae, C., Ayers, K.E., Kim, Y.S. Mater. Chem. A 2021 , 9, 22670-22683 Matanovic, I., Kim, Y.S. Current Opinion in Electrochemistry 2023 , 38, 101218 Leonard, D.P., Lehmann, M., Klein, J.M., Matanovic, I., Fujimoto, C., Saito, T., Kim, Y.S. Advanced Energy Materials 2023 , 13, 2203488
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Singh, Siddhant, Wei Lu, Jeff Sakamoto, and David G. Kwabi. "Electrochemical Desalination Using a Hybrid Redox Flow Cell." ECS Meeting Abstracts MA2022-01, no. 55 (July 7, 2022): 2285. http://dx.doi.org/10.1149/ma2022-01552285mtgabs.
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Electrochemical desalination is an attractive, energy-efficient strategy for small-scale, distributed water purification systems, as compared to conventional thermal desalination or reverse osmosis. Many incumbent electrochemical desalination cells feature a combination of sodium-intercalating electrodes and polymer-based anion-exchange membranes with non-ideal permselectivities. We propose a hybrid flow cell design that features a redox-active electrolyte separated by a cation exchange membrane from a solid, anion-converting or anion-intercalating electrode. This design makes use of a dense, ceramic membrane with a greater selectivity for sodium ion conduction than polymeric ion-exchange membranes, which are also susceptible to energy losses from water crossover between dilute and concentrated salt streams. We discuss considerations that will impact the relationship among electrode and electrolyte properties, operational parameters (e.g. current density, concentration factor and water recovery percentage) and the energetic cost of desalination.
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Nikolic, Nikola, Björn Eriksson, Rakel Lindstrom, Carina Lagergren, and Göran Lindbergh. "Hydrogen Crossover in Anion Exchange Membrane Fuel Cells." ECS Meeting Abstracts MA2023-02, no. 39 (December 22, 2023): 1912. http://dx.doi.org/10.1149/ma2023-02391912mtgabs.
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In recent years anion exchange membrane fuel cells (AEMFC) have started to draw more attention by potentially allowing catalysts based on more abundant materials, and by showing high performance [1]. One often overlooked parameter in these systems is membrane permeability of hydrogen, often referred to as hydrogen crossover, which directly affects fuel cell stability and efficiency. This undesirable effect creates mixed potential due to the permeated hydrogen reacting with oxygen on the cathode, and not generating useful electric energy, only water and heat [2]. The generated heat creates hotspots of temperatures enough to cause membrane defects or even destruction which further accelerates the degrading process [3]. During fuel cell operation relative humidity (RH) and temperature varies in the system, therefore in this study hydrogen crossover is measured at different temperatures (between 50 and 70 ⁰C) and RH (between 30 and 100 %), on Aemion anion exchange membranes (AEMs) with and without reinforcement and with a variety of membrane thicknesses (25 and 50 μm in Figure 1. a). The hydrogen crossover is measured using a mass spectrometer (MS) at the inert gas exhaust. To avoid effects of other components pure membranes and gas diffusion layers (GDLs) were utilized without electrodes. It is shown that AEMs increase in permeability with temperature for all tested while the effect of RH depends on if they are reinforced or not (Figure 1. a). The non-reinforced membranes show a constant decrease in hydrogen crossover with increasing RH, while the reinforced show constant hydrogen crossover until full humidification where it sharply decreases. While the observed trends are different, the quantitative values between reinforced and non-reinforced membranes were relatively similar: at dry conditions, RHs lower than 50 %, crossover is 10 to 30 % lower for reinforced membranes, around 10 % higher at 70 % RH, and at full humidification a non-significant difference compared with non-reinforced (Figure 1. a). It is shown that an increase in the membrane thickness is not proportional to the decrease in hydrogen crossover, suggesting that interface resistance is not negligible. The calculated interface resistance is higher than the bulk resistance for both reinforced and non-reinforced membranes at all RHs (Figure 1. b). However, the bulk resistance is higher for reinforced membranes than for non-reinforced, while interface resistances are relatively similar. Interestingly, the ratio between the interface and the bulk resistance remains constant at all RHs. However, for the membranes without reinforcement the bulk resistance is 20 % of total crossover resistance, while for reinforced it is two times higher, 40 %. Scanning electron microscope (SEM) cross-section analysis shows that the reinforcement is a relatively thin layer of a different polymer in the membrane, which suggests that even a very thin reinforcement could affect membrane permeability properties. Understanding the effects of the reinforcement and their influence on fuel cells will allow for more durable and safer AEMFCs. Figure 1. H2 crossover measured using a MS at the inert gas side. a) At different temperatures, relative humidities and membrane thicknesses. b) H2 crossover resistance at the interface and in the bulk for membranes with and without reinforcement. Measurements are done at 70 °C and at flows 20 ml/min of both hydrogen and the inert gas (Ar). [1] D. R. Dekel, “Review of cell performance in anion exchange membrane fuel cells,” J. Power Sources, vol. 375, pp. 158–169, 2018, doi: 10.1016/j.jpowsour.2017.07.117. [2] S. S. Kocha, J. D. Yang, and J. S. Yi, “Characterization of Gas Crossover and Its Implications in PEM Fuel Cells,” 2006, doi: 10.1002/aic.10780. [3] Q. Tang, B. Li, D. Yang, P. Ming, C. Zhang, and Y. Wang, “Review of hydrogen crossover through the polymer electrolyte membrane,” Int. J. Hydrogen Energy, vol. 46, no. 42, pp. 22040–22061, 2021, doi: 10.1016/j.ijhydene.2021.04.050. Figure 1
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Samsudin, Asep Muhamad, Merit Bodner, and Viktor Hacker. "A Brief Review of Poly(Vinyl Alcohol)-Based Anion Exchange Membranes for Alkaline Fuel Cells." Polymers 14, no. 17 (August 29, 2022): 3565. http://dx.doi.org/10.3390/polym14173565.
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Anion exchange membrane fuel cells have unique advantages and are thus gaining increasing attention. Poly(vinyl alcohol) (PVA) is one of the potential polymers for the development of anion exchange membranes. This review provides recent studies on PVA-based membranes as alternative anion exchange membranes for alkaline fuel cells. The development of anion exchange membranes in general, including the types, materials, and preparation of anion exchange membranes in the last years, are discussed. The performances and characteristics of recently reported PVA-based membranes are highlighted, including hydroxide conductivity, water uptake, swelling degree, tensile strength, and fuel permeabilities. Finally, some challenging issues and perspectives for the future study of anion exchange membranes are discussed.
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Son, Tae Yang, Jun Seong Yun, Kihyun Kim, and Sang Yong Nam. "Electrochemical Performance Evaluation of Bipolar Membrane Using Poly(phenylene oxide) for Water Treatment System." Journal of Nanoscience and Nanotechnology 20, no. 11 (November 1, 2020): 6797–801. http://dx.doi.org/10.1166/jnn.2020.18788.
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This study describes the use of poly(phenylene oxide) polymer-based ion-exchange polymers, polystyrene-based ion-exchange particles and a porous support for fabricating bipolar membranes and the results of an assessment of the applicability of these materials to water splitting. In order to achieve good mechanical as well as good ion-exchange properties, bipolar membranes were prepared by laminating poly(phenylene oxide) and polystyrene based ion-exchange membranes with a sulfonated polystyrene-block-(ethylene-ran-butylene)-block-polystyrene) (S-SEBS) modified interface. PE pore-supported ion-exchange membranes were also used as bipolar membranes. The tensile strength was 13.21 MPa for the bipolar membrane which utilized only a cation/anion-exchange membrane. When ion-exchange nanoparticles were introduced for high efficiency, a reduction in the tensile strength to 6.81 MPa was observed. At the same time, bipolar membrane in the form of a composite membrane using PE support exhibited the best tensile strength of 32.41 MPa. To confirm the water-splitting performance, an important factor for a bipolar membrane, pH changes over a period of 20 min were also studied. During water slitting using CA-P-PE-BPM, the pH at the CEM part and the AEM part changed from 5.4 to 4.18 and from 5.4 to 5.63, respectively.
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Fang, Jun, Chang Ming Zhang, and Yi Xu Yang. "Preparation and Characterization of Polymer Electrolyte Membranes by Radiation Grafted Copolymerization." Advanced Materials Research 485 (February 2012): 110–13. http://dx.doi.org/10.4028/www.scientific.net/amr.485.110.
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Novel anion exchange membranes were synthesized by grafted copolymerization of 1-vinylimidazole onto pre-irradiated ethylene-tetrafluoroethylene copolymer (ETFE) film, followed by quaternization and alkalization. The structure of the membranes was studied by Fourier transform infrared (FT-IR). The physicochemical and electrochemical properties of the membranes were also characterized. The ionic conductivity of the synthesized membrane is 0.03 S/cm at 30°C. This result indicates that the membrane is suitable polymer electrolyte membrane and so may find potential applications in alkaline membrane fuel cells.
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Park, Habin, Chenyu Li, and Paul Kohl. "Durability and Performance of Poly(norbornene) Anion Exchange Membrane Alkaline Electrolyzer with High Ionic Strength Anolyte." ECS Meeting Abstracts MA2024-01, no. 34 (August 9, 2024): 1792. http://dx.doi.org/10.1149/ma2024-01341792mtgabs.
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Anion exchange polymer electrolytes enable low-temperature alkaline water electrolysis for reliable green hydrogen production. Anion exchange membrane water electrolysis (AEMWE) with alkaline electrolytes has several advantages over the proton exchange membrane water electrolysis using acid-based polymer electrolytes. The advantages include low-cost catalysts, all hydrocarbon non-fluorinated polymer membrane, and low-cost cell components. Long-term durability of AEMWEs in high pH operation has been challenging, although there have been significant performance improvements. AEMWE operated at low hydroxide anolyte provides improved chemical stability. In this study, an understanding of the high ionic-strength anolyte is provided along with demonstration of the AEMWE performance and durability. Anion exchange poly(norbornene) solid polymer electrolytes show high-performance, durable membrane electrode assemblies for alkaline electrolysis. Covalently bonded, self-adhesive solid polymer ionomers were used in electrodes for durable electrolysis. Hydration problem with the low pH alkaline anolyte in dry-cathode AEMWE is presented. The effect of anolyte concentration and mobile cations on the cathode electrolysis performance using a low hydroxide anolyte was investigated. High ionic strength anolyte was prepared by changing the mobile cation concentration while maintaining a constant anolyte pH. The mechanism of cathode hydration improvement through use of a high ionic strength anolyte is presented. Long-term durability with the optimal high ionic strength electrolyte is discussed.
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Herring, Andrew M., Mei-Chen Kuo, Ivy Wu, Jack Creel, Marco Salgado, and E. Bryan Coughlin. "Understanding How Anion Exchange Membranes and Cationic Polymer/Catalyst Interactions Behave with Time in Alkaline Electrolysis." ECS Meeting Abstracts MA2023-02, no. 39 (December 22, 2023): 1895. http://dx.doi.org/10.1149/ma2023-02391895mtgabs.
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We are leveraging our existing success with anion exchange membranes (AEM) to develop new highly stable and highly conductive membranes and ionomers for AEM electrolysis. Our novel and scalable tri-block co-polymers ABA or BAB, where the A block can be functionalized with an advanced chemically stable cation and the B block is an unsaturated polymer that when hydrogenated results in high anion conduction membranes with exceptional mechanical strength and durability analogous to polyethylene (PE). We have also developed a novel immobilization technology for processable catalyst inks. Synergistically the A and B block lengths and chemistries are tuned to achieve all the properties desirable for an anion exchange membrane for electrolyzer applications. Random polymers of the same A and B chemistries can also be formulated for additional fidelity in chemically compatible ionomers for the membrane electrode assemblies (MEA). These systems are unique in that they achieve very high dissociation of anions beyond OH-, giving CO3 2- σ<100 mS cm-1 ca. 60°C and enhanced chemical stability as the water is separated from the high MW polyethylene backbone that additionally gives the materials unprecedented strength. This will allow us to fabricate thinner membranes for long durability pressure differentiated operation. Because of the unusual and exceptional CO3 2- conductivity that we have designed into our membrane, we are able to optimize these for a carbonate electrolyte electrolyzer. While we lose a 100 mV in activity compared to operation in OH-, the advantages including high current densities enabled by our novel membrane outweigh that disadvantage. Chemical stability of the membrane is not a concern, and the system is less complicated as we do not need to use expensive components to protect against caustic corrosion or protect the hydroxide electrolyte from carbon dioxide present in air to avoid its inevitable conversion to CO3 2-. Not all proposed AEM polymer chemistries are scalable, many involve too many synthetic steps, suffer from low overall yields, and are highly exothermic reactions (thus only safely executed on a small scale), or do not produce sufficiently high molecular weight for film formation. The polymer systems proposed here have already been demonstrated on the 1 kg scale. This novel AEM intellectual property, jointly invented by Mines and UMass, has been licensed to Spark Ionix who are commercializing an early version of this polymer technology. The next generation of tailored polymers proposed are increasingly robust, scalable, efficient and more amenable to high volume manufacture to produce inexpensive hydrocarbon polymer membranes for use in electrolyzers. The block lengths, overall molecular weight and chemistries are completely tunable to fabricate AEMs with all desired properties or compatible ionomer chemistries that allow high levels of catalyst utilization, through both ionic conductivity and chemical transport. We have been investigating this polymer system in 1M K2CO3 at 50°C with great success and have shown good performance and durability in 5cm2cells. We are developing the system for >60°C and 25 cm2 cells. We have begun to understand the science behind ionomer catalyst interactions and initially used a commercial Ag nano-catalyst as a model system. Few ave studied the effect of ionomer chemistry and catalyst or catalyst type and loadings on performance. We have shown durability of > 600 h at 0.5 A cm-2 and continue to see improvements. It should be noted that the voltage is dropping in theses tests, at end of test at –ve 60 µV h-1 is achieved, while this may be interpreted as evidence of membrane thinning when the cell was dissembled the membrane thickness was ca. the same as at the beginning of test (80 µm), indicating slow, but long term conditioning, the cell did not reach the point at which a +ve degradation rate was observed. Further investigation of cell conditioning indicated that these cells currently take 40-50 hs under load to reach steady state operation (this break in time will be understood and significantly shortened) giving 400MV improvement at 1 A cm-2. With a MnO2 catalyst the voltage at 0.5 A cm-2drops to 1.5 V indicating that the target of 2 A cm-2 at 1.8 V will be easily achieved with further investigation.
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Butylskii, Dmitrii Yu, Vasiliy A. Troitskiy, Maria A. Ponomar, Ilya A. Moroz, Konstantin G. Sabbatovskiy, and Mikhail V. Sharafan. "Efficient Anion-Exchange Membranes with Anti-Scaling Properties Obtained by Surface Modification of Commercial Membranes Using a Polyquaternium-22." Membranes 12, no. 11 (October 29, 2022): 1065. http://dx.doi.org/10.3390/membranes12111065.
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Anion-exchange membranes modified with a polyquaternium-22 (PQ-22) polymer were studied for their use in electrodialysis. The use of PQ-22 for modification makes it possible to “replace” weakly basic amino groups on the membrane surface with quaternary amino groups. It was found that the content of quaternary amino groups in PQ-22 is higher than the content of carboxyl groups, which is the reason for the effectiveness of this polymer even when modifying Ralex AHM-PES membranes that initially contain only quaternary amino groups. In the case of membranes containing weakly basic amino groups, the PQ-22 polymer modification efficiency is even higher. The surface charge of the modified MA-41P membrane increased, while the limiting current density on the current-voltage curves increased by more than 1.5 times and the plateau length decreased by 2.5 times. These and other characteristics indicate that the rate of water splitting decreased and the electroconvective mixing at the membrane surface intensified, which was confirmed by direct visualization of vortex structures. Increasing the surface charge of the commercial MA-41P anion-exchange membrane, reducing the rate of water splitting, and enhancing electroconvection leads to mitigated scaling on its surface during electrodialysis.
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Chen, Nanjun, Hong Zhu, Yuhao Chu, Rui Li, Yang Liu, and Fanghui Wang. "Cobaltocenium-containing polybenzimidazole polymers for alkaline anion exchange membrane applications." Polymer Chemistry 8, no. 8 (2017): 1381–92. http://dx.doi.org/10.1039/c6py01936f.
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Eti, Mine, Aydın Cihanoğlu, Enver Güler, Lucia Gomez-Coma, Esra Altıok, Müşerref Arda, Inmaculada Ortiz, and Nalan Kabay. "Further Development of Polyepichlorohydrin Based Anion Exchange Membranes for Reverse Electrodialysis by Tuning Cast Solution Properties." Membranes 12, no. 12 (November 26, 2022): 1192. http://dx.doi.org/10.3390/membranes12121192.
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Recently, there have been several studies done regarding anion exchange membranes (AEMs) based on polyepichlorohydrin (PECH), an attractive polymer enabling safe membrane fabrication due to its inherent chloromethyl groups. However, there are still undiscovered properties of these membranes emerging from different compositions of cast solutions. Thus, it is vital to explore new membrane properties for sustainable energy generation by reverse electrodialysis (RED). In this study, the cast solution composition was easily tuned by varying the ratio of active polymer (i.e., blend ratio) and quaternary agent (i.e., excess diamine ratio) in the range of 1.07–2.00, and 1.00–4.00, respectively. The membrane synthesized with excess diamine ratio of 4.00 and blend ratio of 1.07 provided the best results in terms of ion exchange capacity, 3.47 mmol/g, with satisfactory conductive properties (area resistance: 2.4 Ω·cm2, electrical conductivity: 6.44 mS/cm) and high hydrophilicity. RED tests were performed by AEMs coupled with the commercially available Neosepta CMX cation exchange membrane (CEMs).
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Thangarasu, Sadhasivam, and Tae-Hwan Oh. "Recent Developments on Bioinspired Cellulose Containing Polymer Nanocomposite Cation and Anion Exchange Membranes for Fuel Cells (PEMFC and AFC)." Polymers 14, no. 23 (December 1, 2022): 5248. http://dx.doi.org/10.3390/polym14235248.
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Hydrogen fuel cell (FC) technologies are being worked on as a possible replacement for fossil fuels because they produce a lot of energy and do not pollute the air. In FC, ion-exchange membranes (IEMs) are the vital components for ion transport between two porous electrodes. However, the high production cost of commercialized membranes limits their benefits. Various research has focused on cellulose-based membranes such as IEM with high proton conductivity, and mechanical, chemical, and thermal stabilities to replace the high cost of synthetic polymer materials. In this review, we focus on and explain the recent progress (from 2018 to 2022) of cellulose-containing hybrid membranes as cation exchange membranes (CEM) and anion exchange membranes (AEM) for proton exchange membrane fuel cells (PEMFC) and alkaline fuel cells (AFC). In this account, we focused primarily on the effect of cellulose materials in various membranes on the functional properties of various polymer membranes. The development of hybrid membranes with cellulose for PEMFC and AFC has been classified based on the combination of other polymers and materials. For PEMFC, the sections are associated with cellulose with Nafion, polyaryletherketone, various polymeric materials, ionic liquid, inorganic fillers, and natural materials. Moreover, the cellulose-containing AEM for AFC has been summarized in detail. Furthermore, this review explains the significance of cellulose and cellulose derivative-modified membranes during fuel cell performance. Notably, this review shows the vital information needed to improve the ion exchange membrane in PEMFC and AFC technologies.
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Bae, Chulsung. "(Invited) Molecular Engineering of Ion-Conducting Polymer Membranes for Electrochemical Energy Storage and Conversion Technologies." ECS Meeting Abstracts MA2022-01, no. 39 (July 7, 2022): 1731. http://dx.doi.org/10.1149/ma2022-01391731mtgabs.
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Anion exchange membranes (AEMs) based on hydroxide-conducting polymers are a key component for anion-based electrochemical energy technology such as fuel cells, electrolyzers, and advanced batteries. Although these alkaline electrochemical technologies offer a promising alternative to acidic proton exchange membrane electrochemical devices, the access to chemically stable, mechanically durable, high-performing polymer electrolyte materials has been bottleneck to advance electrochemical technologies for hydrogen and other green chemicals until now. Despite vigorous research of AEM polymer design, examples of high-performance polymers with good alkaline stability at an elevated temperature are uncommon. Traditional aromatic polymers used in AEM applications contain a heteroatomic backbone linkage which is prone to degradation via nucleophilic attack by hydroxide ion. In this presentation, I will highlight recent progress at the Bae group of Rensselaer Polytechnic Institute in the development of advanced hydroxide-conducting polymers and membranes for AEM technology applications. We have developed a number of synthetic methodologies that produce polymer design made of all C−C bond backbones and a flexible chain-tethered quaternary ammonium group and that provide an effective solution to the problem of alkaline stability. The advantage of good solvent processability, synthetic versatility, and convenient scalability of the reaction process has generated considerable interest of these polymers, and they are considered leading candidates for commercial standard AEM. AEM fuel cells, electrolyzer, and redox flow battery tests of some of the developed polymer membranes showed excellent performance, suggesting that this new class of AEMs open a new avenue to electrochemical devices with real-world applications.
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Veh, Philipp, Benjamin Britton, Steven Holdcroft, Roland Zengerle, Severin Vierrath, and Matthias Breitwieser. "Improving the water management in anion-exchange membrane fuel cells via ultra-thin, directly deposited solid polymer electrolyte." RSC Advances 10, no. 15 (2020): 8645–52. http://dx.doi.org/10.1039/c9ra09628k.
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Phua, Yin Kan, Tsuyohiko Fujigaya, and Koichiro Kato. "Nuclear Magnetic Resonance Chemical Shift As Highly Explainable Chemical Structure Fingerprints for Anion Exchange Membrane Polymers." ECS Meeting Abstracts MA2023-02, no. 65 (December 22, 2023): 3153. http://dx.doi.org/10.1149/ma2023-02653153mtgabs.
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Recent shift towards clean energy increased the demand for both fuel cells (used as clean power generator) and water electrolyzer (used as hydrogen supply) significantly. Anion exchange membrane (AEM) serves as a core component for these devices, though its low anion conductivity and durability inhibit their potential for commercialization. Many research and development (R&D) have been done seeking for improvements in AEM1, but current empirical-centric method consumes significant amount of resources, such as cost, labor, and time. To reduce resource consumptions, implementing materials informatics (MI) that allows high-speed screening of materials through a pre-trained AEM polymer machine learning (ML) model is important. However, AEMs are made up of polymers whose chemical structures are complex and hard to represent in a machine-understandable form. Fingerprints are often used to represent chemical structures in numerical forms generated through algorithm2. Majority of these fingerprints are designed for small molecules, not polymers, but they are usually unintuitive and difficult to understand due to their topological nature. In contrast, nuclear magnetic resonance (NMR) chemical shift have long been used in chemistry to identify the chemical structure of a particular sample3. In this study, we aim to utilize the high-resolution nature of NMR chemical shift to identify structural formula as chemical structure fingerprint for ML model, such that a polymer-suited and highly explainable fingerprint can be developed. First, an AEM database containing structural and experimental condition information was built using data extracted from 62 papers. Experimental conditions included were anion conductivity measuring temperature, alkaline stability test measuring condition (test temperature, length of test, and concentration of alkaline solution). Then, the 13C NMR chemical shift for the chemical structure contained in structural information was calculated using ChemDraw. The obtained chemical shifts were converted to numerical strings and is named as “NMR fingerprint”. A new AEM database containing both structural (molar ratio of each building blocks and NMR fingerprints) and experimental condition was used as the training database for ML models. Target variable was set to anion conductivity, and the rest were explanatory variables. ML model used was XGBoost. Cross-validation was used to evaluate the capability of ML models to predict anion conductivity of novel AEM polymers. Prediction logic was analyzed using Shapley additive explanations (SHAP) value. The database built contains data from 62 AEM papers, with 2,197 anion conductivity data points. Each AEM chemical structures present in the database was converted to NMR fingerprints using NMR chemical shifts, obtaining around 2,000 NMR fingerprints for each AEM polymer unit. Together with the experimental conditions and structural information included in the database, the data were used as train-validation dataset for XGBoost. The coefficient of determination (R2) obtained for cross-validated model was 0.9235, implying that the model learnt and determined the relationship between anion conductivity and AEM polymer structure with high accuracy, with the aid of experimental conditions. Then, the prediction logic of the ML model was explored using SHAP values, which are values computed from coalitional game theory, and is used to increase transparency and interpretability of ML models. Analyzing the plot of SHAP values for top 20 important variables used in XGBoost showed that measuring temperature for anion conductivity ranked highest, which is in coherence to the well-known behavior of AEM polymers. Besides, non-experimental condition variables such as 29.8_A ranked into the top 3 important variables. 29.8_A is the chemical shift for alkyl groups attached in between two imidazolium group of AEM polymer, suggesting that the presence or absence of more than one imidazolium group per side chain is important to determine the anion conductivity of an AEM polymer. SHAP values for 29.8_A show that higher feature value (pink color) gives higher impact (positive region of x-axis) to the target variable, inferring that having alkyl groups between imidazolium groups give beneficial effect to anion conductivity. Such ability to explain the prediction logic of ML model shows that using NMR chemical shifts as fingerprints for AEM polymer structures provide intuitive, human-understandable ML prediction logic explanation. Together with the high cross-validation accuracy, NMR chemical shifts hold the potential to not only be a gold standard in expressing polymer structures in machine-understandable form, but also to strongly push the adoption of ML in the AEM polymer field, creating a paradigm shift for AEM R&D. Reference S. Gottesfeld et al., J. Power Sources 2018, 375, 170-184. J. Bajorath, J. Chem. Inf. Comput. Sci. 2001, 41, 2, 233–245. P. Jezzard et al., Adv. Mater. 1992, 4, 2, 82-90. Figure 1
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Koch, Susanne, Joey Disch, Sophia K. Kilian, Lukas Metzler, and Severin Vierrath. "Water Transport and Salt Precipitation in Anion-Exchange Membrane Electrolyzers." ECS Meeting Abstracts MA2023-02, no. 42 (December 22, 2023): 2068. http://dx.doi.org/10.1149/ma2023-02422068mtgabs.
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The hydrophilic nature of hydrocarbon ionomers and membranes presents a major challenge in anion-exchange membrane (AEM) electrolysis, despite improved stability from reinforcements and modified polymer chemistry. Durability and performance are still highly influenced by the operation mode and water management within the membrane-electrode-assembly (MEA). Dry cathode operation in AEM water electrolysis, where only the anode is supplied with liquid electrolyte (KOH), offers increased hydrogen purity but poses challenges for non-fluorinated anion-exchange polymers that are sensitive to water content. In-situ neutron imaging with high resolution (~6 µm effective resolution) revealed that adjusting the anion-exchange capacity of the cathode binder ionomer can retain membrane humidification (Fig. 1)1. In the electrochemical reduction of CO2 using AEM, water management and salt precipitation are significant challenges. High-resolution neutron imaging of a zero-gap CO2 electrolyzer operating at 200 mA cm-² and 2.8 V showed salt precipitates penetrating the cathode gas diffusion layer, leading to blocked CO2 gas transport and a decay in Faraday efficiency. Salt accumulation was higher under the cathode channel of the flow field than the land2. Both studies demonstrate the substantial impact of water management and salt precipitation on the operation of AEM-based electrolyzers and how neutron imaging can assist in addressing these challenges. References (1) Koch, S.; Disch, J.; Kilian, S. K.; Han, Y.; Metzler, L.; Tengattini, A.; Helfen, L.; Schulz, M.; Breitwieser, M.; Vierrath, S. Water management in anion-exchange membrane water electrolyzers under dry cathode operation. RSC Adv 2022, 12, 20778–20784. (2) Disch, J.; Bohn, L.; Koch, S.; Schulz, M.; Han, Y.; Tengattini, A.; Helfen, L.; Breitwieser, M.; Vierrath, S.; High-resolution neutron imaging of salt precipitation and water transport in zero-gap CO2 electrolysis. Nat Commun 2022, 13, 6099. Figure 1
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Ji, Yuanyuan, Hongxi Luo, and Geoffrey M. Geise. "Effects of fixed charge group physicochemistry on anion exchange membrane permselectivity and ion transport." Physical Chemistry Chemical Physics 22, no. 14 (2020): 7283–93. http://dx.doi.org/10.1039/d0cp00018c.
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Understanding the effects of polymer chemistry on membrane ion transport properties is critical for enabling efforts to design advanced highly permselective ion exchange membranes for water purification and energy applications.
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Atlaskin, A. A., A. A. Andronova, and O. V. Kazarina. "Thermal Decomposition Characteristics of Poly((4-Vinylbenzyl) Trimethylammonium Bis (Trifluoromethanesulfonimide)) Studied by Pyrolysis-GS / MS." Key Engineering Materials 887 (May 2021): 91–97. http://dx.doi.org/10.4028/www.scientific.net/kem.887.91.
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Over the past decades, significant advances have been made in the development and research of gas separation membranes based on ionic liquids (IL) and their polymer analogs (PIL) for membrane separation of "acid gases" such as CO2 and H2S from gas mixtures. Polymers containing various amino groups are of great interest for the selective separation of acid gases from gas mixtures, since ammonia and its derivatives are used in conventional purification. In this work, we have synthesized a monomeric ionic liquid based on 4 vinylbenzyl chloride with included triethylamine by the Menshutkin reaction. Further, on its basis, polymer ionic liquids were obtained by the method of free radical polymerization, then an anion exchange reaction was carried out to replace the Cl anion with Tf2N. To analyze the process of thermal pyrolysis of poly [VBTEA-Tf2N] a pyrolysis-gas chromatography/mass spectrometer (Py-GC/MS) was employed in this research. The obtained materials, which are high molecular weight compounds, can be used to obtain polymer membranes of various architectures by traditional methods: both non-porous symmetric membranes and microporous asymmetric membranes.
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Shang, Zhihao, Ryszard Wycisk, and Peter Pintauro. "Electrospun Composite Proton-Exchange and Anion-Exchange Membranes for Fuel Cells." Energies 14, no. 20 (October 15, 2021): 6709. http://dx.doi.org/10.3390/en14206709.
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A fuel cell is an electrochemical device that converts the chemical energy of a fuel and oxidant into electricity. Cation-exchange and anion-exchange membranes play an important role in hydrogen fed proton-exchange membrane (PEM) and anion-exchange membrane (AEM) fuel cells, respectively. Over the past 10 years, there has been growing interest in using nanofiber electrospinning to fabricate fuel cell PEMs and AEMs with improved properties, e.g., a high ion conductivity with low in-plane water swelling and good mechanical strength under wet and dry conditions. Electrospinning is used to create either reinforcing scaffolds that can be pore-filled with an ionomer or precursor mats of interwoven ionomer and reinforcing polymers, which after suitable processing (densification) form a functional membrane. In this review paper, methods of nanofiber composite PEMs and AEMs fabrication are reviewed and the properties of these membranes are discussed and contrasted with the properties of fuel cell membranes prepared using conventional methods. The information and discussions contained herein are intended to provide inspiration for the design of high-performance next-generation fuel cell ion-exchange membranes.
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Lee, Ming-Tsung. "Functionalized Triblock Copolymers with Tapered Design for Anion Exchange Membrane Fuel Cells." Polymers 16, no. 16 (August 22, 2024): 2382. http://dx.doi.org/10.3390/polym16162382.
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Triblock copolymers such as styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) have been widely used as an anion exchange membrane for fuel cells due to their phase separation properties. However, modifying the polymer architecture for optimized membrane properties is still challenging. This research develops a strategy to control the membrane morphology based on quaternized SEBS (SEBS-Q) by dual-tapering the interfacial block sequences. The structural and transport properties of SEBS-Q with various tapering styles at different hydration levels are systematically investigated by coarse-grained molecular simulations. The results show that the introduction of the tapered regions induces the formation of a bicontinuous water domain and promotes the diffusivity of the mobile components. The interplay between the solvation of the quaternary groups and the tapered fraction determines the conformation of polymer chains among the hydrophobic–hydrophilic subdomains. The strategy presented here provides a new path to fabricating fuel cell membranes with controlled microstructures.
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Feng, Zhiming, Gaurav Gupta, and Mohamed Mamlouk. "Degradation of QPPO-based anion polymer electrolyte membrane at neutral pH." RSC Advances 13, no. 29 (2023): 20235–42. http://dx.doi.org/10.1039/d3ra02889e.
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Pismenskaya, Natalia, Veronika Sarapulova, Anastasia Klevtsova, Sergey Mikhaylin, and Laurent Bazinet. "Adsorption of Anthocyanins by Cation and Anion Exchange Resins with Aromatic and Aliphatic Polymer Matrices." International Journal of Molecular Sciences 21, no. 21 (October 23, 2020): 7874. http://dx.doi.org/10.3390/ijms21217874.
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This study examines the mechanisms of adsorption of anthocyanins from model aqueous solutions at pH values of 3, 6, and 9 by ion-exchange resins making the main component of heterogeneous ion-exchange membranes. This is the first report demonstrating that the pH of the internal solution of a KU-2-8 aromatic cation-exchange resin is 2-3 units lower than the pH of the external bathing anthocyanin-containing solution, and the pH of the internal solution of some anion-exchange resins with an aromatic (AV-17-8, AV-17-2P) or aliphatic (EDE-10P) matrix is 2–4 units higher than the pH of the external solution. This pH shift is caused by the Donnan exclusion of hydroxyl ions (in the KU-2-8 resin) or protons (in the AV-17-8, AV-17-2P, and EDE-10P resins). The most significant pH shift is observed for the EDE-10P resin, which has the highest ion-exchange capacity causing the highest Donnan exclusion. Due to the pH shift, the electric charge of anthocyanin inside an ion-exchange resin differs from its charge in the external solution. At pH 6, the external solution contains uncharged anthocyanin molecules. However, in the AV-17-8 and AV-17-2P resins, the anthocyanins are present as singly charged anions, while in the EDE-10P resin, they are in the form of doubly charged anions. Due to the electrostatic interactions of these anions with the positively charged fixed groups of anion-exchange resins, the adsorption capacities of AV-17-8, AV-17-2P, and EDE-10P were higher than expected. It was established that the electrostatic interactions of anthocyanins with the charged fixed groups increase the adsorption capacity of the aromatic resin by a factor of 1.8–2.5 compared to the adsorption caused by the π–π (stacking) interactions. These results provide new insights into the fouling mechanism of ion-exchange materials by polyphenols; they can help develop strategies for membrane cleaning and for extracting anthocyanins from juices and wine using ion-exchange resins and membranes.
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Zhou, Hengcheng, Peihai Ju, Shaowei Hu, Lili Shi, Wenjing Yuan, Dongdong Chen, Yujie Wang, and Shaoyuan Shi. "Separation of Hydrochloric Acid and Oxalic Acid from Rare Earth Oxalic Acid Precipitation Mother Liquor by Electrodialysis." Membranes 13, no. 2 (January 27, 2023): 162. http://dx.doi.org/10.3390/membranes13020162.
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In this study, the hydrochloric acid from rare earth oxalic acid precipitation mother liquor was separated by electrodialysis (ED) with different anion exchange membranes, including selective anion exchange membrane (SAEM), polymer alloy anion exchange membrane (PAAEM), and homogenous anion exchange membrane (HAEM). In addition to actual wastewater, nine types of simulated solutions with different concentrations of hydrochloric acid and oxalic acid were used in the experiments. The results indicated that the hydrochloric acid could be separated effectively by electrodialysis with SAEM from simulated and real rare earth oxalic acid precipitation mother liquor under the operating voltage 15 V and ampere 2.2 A, in which the hydrochloric acid obtained in the concentrate chamber of ED is of higher purity (>91.5%) generally. It was found that the separation effect of the two acids was related to the concentrations and molar ratios of hydrochloric acid and oxalic acid contained in their mixtures. The SEM images and ESD–mapping analyses indicated that membrane fouling appeared on the surface of ACS and CSE at the diluted side of the ED membrane stack when electrodialysis was used to treat the real rare earth oxalic acid precipitation mother liquor. Fe, Yb, Al, and Dy were found in the CSE membrane section, and organic compounds containing carbon and sulfur were attached to the surface of the ACS. The results also indicated that the real rare earth precipitation mother liquor needed to be pretreated before the separation of hydrochloric acid and oxalic acid by electrodialysis.
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Letsau, Thabakgolo T., Penny P. Govender, and Phumlani F. Msomi. "Imidazolium-Quaternized Poly(2,6-Dimethyl-1,4-Phenylene Oxide)/Zeolitic Imidazole Framework-8 Composite Membrane as Polymer Electrolyte for Fuel-Cell Application." Polymers 14, no. 3 (February 1, 2022): 595. http://dx.doi.org/10.3390/polym14030595.
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Anion exchange membrane fuel cells (AEMFCs) are considered superior to their counterpart proton exchange fuel cells due to their many advantages. Both fuel cells use membranes as polymer electrolytes to improve fuel-cell properties and power output. This work evaluates a series of imidazolium-quaternized poly(2,6-dimethyl-1,4-phenylene oxide) (ImPPO) functionalized zeolitic imidazole framework-8 (ZIF-8) (ImPPO/ZIF-8) as anion exchange membrane (AEM) electrolytes in a direct methanol alkaline fuel cell. FTIR and 1H NMR were used to confirm the successful membrane fabrication. SEM and TGA were used to study the morphological and thermal stability properties of the ImPPO/ZIF-8 membranes. The AEMs obtained in this work had contact angles ranging from 55.27–106.73°, water uptake from 9–83%, ion exchange capacity (IEC) from 1.93–3.15 mmol/g, and ion conductivity (IC) from 1.02–2.43 mS/cm. The best-performing membrane, ImPPO/3%ZIF-8, showed a water uptake of up to 35% at 80 °C, a swelling ratio of 15.1% after 72 h, IEC of 4.06 mmol/g, and IC of 1.96 mS/cm. A power density of 158.10 mW/cm2 was obtained. This makes ZIF-8 a good prospect as a filler for enhancing membrane properties.
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Mamlouk, M., J. A. Horsfall, C. Williams, and K. Scott. "Radiation grafted membranes for superior anion exchange polymer membrane fuel cells performance." International Journal of Hydrogen Energy 37, no. 16 (August 2012): 11912–20. http://dx.doi.org/10.1016/j.ijhydene.2012.05.117.
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Terin, Denis, Marina Kardash, Denis Ainetdinov, Timur Turaev, and Ilya Sinev. "Anion-Exchange Membrane “Polikon A” Based on Polyester Fiber Fabric (Functionalized by Low-Temperature High-Frequency Plasma) with Oxidized Metal Nanoparticles." Membranes 13, no. 8 (August 18, 2023): 742. http://dx.doi.org/10.3390/membranes13080742.
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An experimental laboratory set of samples of composite heterogeneous anion-exchange membranes was obtained by us for the development of our original method of polycondensation filling. Anion-exchange membranes were prepared on plasma-treated and non-plasma-treated polyester fiber fabrics. The fabric was treated with low-temperature argon plasma at a power of 400 W for 10 min at a pressure of 5 × 10−5 mbar. On the surface and bulk of the polyester fiber, a polyfunctional anionite of mixed basicity was synthesized and formed. The anion-exchange membrane contained secondary and tertiary amino groups and quaternary ammonium groups, which were obtained from polyethylene polyamines and epichlorohydrins. At the stage of the chemical synthesis of the anion matrix, oxidized nanoparticles (~1.5 wt.%) of silicon, nickel, and iron were added to the monomerization composition. The use of ion-plasma processing of fibers in combination with the introduction of oxidized nanoparticles at the synthesis stage makes it possible to influence the speed and depth of the synthesis and curing processes; this changes the formation of the surface morphology and the internal structure of the ion-exchange polymer matrix, as well as the hydrophobic/hydrophilic balance and—as a result—the different operational characteristics of anion-exchange membranes.
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Ge, Qianqian, Yazhi Liu, Zhengjin Yang, Bin Wu, Min Hu, Xiaohe Liu, Jianqiu Hou, and Tongwen Xu. "Hyper-branched anion exchange membranes with high conductivity and chemical stability." Chemical Communications 52, no. 66 (2016): 10141–43. http://dx.doi.org/10.1039/c6cc04930c.
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Das, Gautam, Ji-Hyeok Choi, Phan Khanh Thinh Nguyen, Dong-Joo Kim, and Young Soo Yoon. "Anion Exchange Membranes for Fuel Cell Application: A Review." Polymers 14, no. 6 (March 16, 2022): 1197. http://dx.doi.org/10.3390/polym14061197.
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The fuel cell industry is the most promising industry in terms of the advancement of clean and safe technologies for sustainable energy generation. The polymer electrolyte membrane fuel cell is divided into two parts: anion exchange membrane fuel cells (AEMFCs) and proton exchange membrane fuel cells (PEMFCs). In the case of PEMFCs, high-power density was secured and research and development for commercialization have made significant progress. However, there are technical limitations and high-cost issues for the use of precious metal catalysts including Pt, the durability of catalysts, bipolar plates, and membranes, and the use of hydrogen to ensure system stability. On the contrary, AEMFCs have been used as low-platinum or non-platinum catalysts and have a low activation energy of oxygen reduction reaction, so many studies have been conducted to find alternatives to overcome the problems of PEMFCs in the last decade. At the core of ensuring the power density of AEMFCs is the anion exchange membrane (AEM) which is less durable and less conductive than the cation exchange membrane. AEMFCs are a promising technology that can solve the high-cost problem of PEMFCs that have reached technological saturation and overcome technical limitations. This review focuses on the various aspects of AEMs for AEMFCs application.
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Düerkop, Dennis, Hartmut Widdecke, Carsten Schilde, Ulrich Kunz, and Achim Schmiemann. "Polymer Membranes for All-Vanadium Redox Flow Batteries: A Review." Membranes 11, no. 3 (March 18, 2021): 214. http://dx.doi.org/10.3390/membranes11030214.
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Redox flow batteries such as the all-vanadium redox flow battery (VRFB) are a technical solution for storing fluctuating renewable energies on a large scale. The optimization of cells regarding performance, cycle stability as well as cost reduction are the main areas of research which aim to enable more environmentally friendly energy conversion, especially for stationary applications. As a critical component of the electrochemical cell, the membrane influences battery performance, cycle stability, initial investment and maintenance costs. This review provides an overview about flow-battery targeted membranes in the past years (1995–2020). More than 200 membrane samples are sorted into fluoro-carbons, hydro-carbons or N-heterocycles according to the basic polymer used. Furthermore, the common description in membrane technology regarding the membrane structure is applied, whereby the samples are categorized as dense homogeneous, dense heterogeneous, symmetrical or asymmetrically porous. Moreover, these properties as well as the efficiencies achieved from VRFB cycling tests are discussed, e.g., membrane samples of fluoro-carbons, hydro-carbons and N-heterocycles as a function of current density. Membrane properties taken into consideration include membrane thickness, ion-exchange capacity, water uptake and vanadium-ion diffusion. The data on cycle stability and costs of commercial membranes, as well as membrane developments, are compared. Overall, this investigation shows that dense anion-exchange membranes (AEM) and N-heterocycle-based membranes, especially poly(benzimidazole) (PBI) membranes, are suitable for VRFB requiring low self-discharge. Symmetric and asymmetric porous membranes, as well as cation-exchange membranes (CEM) enable VRFB operation at high current densities. Amphoteric ion-exchange membranes (AIEM) and dense heterogeneous CEM are the choice for operation mode with the highest energy efficiency.
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Wu, Ivy, Mei-Chen Kuo, Kevin Dunn, Jack Creel, Andrew Johnson, Kaylee Beiler, and Andrew M. Herring. "Using a Tunable Triblock Cationic Polymer to Unravel Performance and Durability Effects in Anion Exchange Membrane Based Electrolysis." ECS Meeting Abstracts MA2023-01, no. 36 (August 28, 2023): 2030. http://dx.doi.org/10.1149/ma2023-01362030mtgabs.
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The use of anion exchange membranes (AEMs) as the polymer electrolyte membrane and related cationic polymers as ionomers in the electrodes of water splitting electrolyzers could lead to significant advantages including the elimination of precious metal electrocatalysts. Because oxygenated radicals in base have a very much lower half life than in acid these materials can be based on hydrocarbon backbones. This leads to an enormous possible variation in polymer chemistry and, while exciting from the point of view of the creation of new polymer chemistries, has led to a lack of detail in determining exactly how all of these many polymers really behave in terms of performance and durability. All of the new materials that are currently being commercialized are designed to be free standing films that are chemically stable to attack by the strongly nucleophilic hydroxide anion. Often these polymers have excessive swelling and poor mechanical properties and lack easy variation enabling their modification to the properties required for an ionomer. Studies where the effect of film processing on performance or durability are also lacking. There is a chronic lack of knowledge in how cationic polymers interact with catalyst particles, charge carrier and the AEM in electrodes. Further complicating these studies is whether the device is operated in water, carbonate or hydroxide solution. The first of which give unexpectedly low performance but may be more amenable to long durability and latter of which gives high performance and low durability. We have developed a triblock co-polymer, with polychlorostyrene blocks that can be quaternized to give a hydrophilic phase and a central hydrophobic polyethylene (pE) block that gives the material good mechanical properties. This seemingly simple system can show tremendous variations. We can control the polymer block lengths and overall molecular weight of the polymer. The material can be suspension cast or melt processed to obtain uniform films. The films are post-quaternized and we can control the degree of functionalization and the nature of the cation. What is interesting about these materials is that for all anions that we have studied their conductivity behavior indicates that they are fully dissociated. We hypothesize that the pE content of the films localizes the water, this has the effect of both promoting anion conduction and also not wetting much of the polymer and so improving the durability and mechanical properties. In a series of films where we systematically increase the pE content, the materials swell less but do not necessarily loose performance. They do however show durability improvements, where a material that is 50% pE will thin in an electrolysis test giving rise to a degradation rate of -23 mV/h, a material with 80% pE will show a degradation rate of +400mV/h, at 500 μA/cm2. Further understanding of these materials is likely to result in further durability improvements. Performance and durability can also be varied by the method by which the film is processed. By using an unsaturated version of the cationic triblock co-polymer in electrode formulations and post hydrogenating we can insolubilize the polymer (by creating an insoluble pE containing polymer insitu) as the ionomer in the electrode. This allows us to study, ionomer loading and to begin to control the positioning of the ionomer. We have baselined these materials using Ni supports, and studied Membrane electrode assemblies on our optimized membranes. These ionomers are surprisingly durable as they contain aromatic groups, leading to further speculation that the localization of the water in the material again gives performance and durability advantages. In this talk we will also show how ionomer chemistry can be used to improve the performance and durability of electrolysis electrodes with either silver, cobalt oxide, or manganese oxide.
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Parajuli, D., N. Murali, K. Samatha, N. L. Sahu, and B. R. Sharma. "Anion Exchange Membrane Functionalized by Phenol-formaldehyde Resins: Ion Exchange Capacity, Electrical Properties, Chemical Stability, Permeability, and All-iron Flow Battery." Journal of Nepal Physical Society 9, no. 2 (December 31, 2023): 47–55. http://dx.doi.org/10.3126/jnphyssoc.v9i2.62322.
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An anion exchange membrane (AEM) is a type of selectively permeable membrane that facilitates the movement of negatively charged ions while impeding the passage of positively charged ions. These membranes are designed to selectively transport anions across them based on their charge and size. They are commonly used in various electrochemical devices and processes, such as fuel cells, electrodialysis, electrolysis, water treatment, and other applications requiring ion exchange. These membranes are typically made from synthetic polymer materials with positively charged functional groups that attract and transport anions while repelling cations. They are used for selection, conduction, and stabilizing the ion anion exchange phenomena. We recently released a study on the creation of a quick and easy approach to creating an AEM with increased ionic conduction capacity and good alkaline stability. The technique's simplicity makes it a desirable substitute for conventional methods. By using this approach, the carcinogenic reagent often employed for AEM preparation—chloromethyl methyl ether—is avoided. Membrane surfaces appeared to be rather homogeneous in Scanning Electron Microscope (SEM) pictures. Water content, ion exchange capacity, and electrical conductivity all improved as the amount of ion-exchange material in the casting fluid increased. The Thermogravimetric Analysis (TGA) of the membranes revealed thermal stability up to 150°C which shows that these membranes are ideal for applications in that temperature range. The composite membranes exhibited enhanced chemical stability in strong chemical environments and this can be attributed to the resonance stabilized guanidine group as negative ion-exchange site. By considering the AC impedance data, the conductivity measurements showed a marked enhancement in conductivity by increasing the content of ion-exchange material. Galvanostatic charged discharge tests were used to examine the electrochemical performance of an all-iron redox flow cell, and the system demonstrated a columbic efficiency of 80% during the repeated charge-discharge cycles. The findings of this work provide a compelling alternative to the established methods for the synthesis of AEMs.
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Sun, Pengzhan, Kunlin Wang, Jinquan Wei, Minlin Zhong, Dehai Wu, and Hongwei Zhu. "Effective recovery of acids from iron-based electrolytes using graphene oxide membrane filters." J. Mater. Chem. A 2, no. 21 (2014): 7734–37. http://dx.doi.org/10.1039/c4ta00668b.
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Efficient recovery of acids from iron-based electrolytes using GO membranes was demonstrated. The trans-membrane transport of H+ was two orders of magnitude greater than that of Fe3+. The circular penetration of iron-based electrolytes could produce acids with high purity, which was superior to other traditional diffusion dialysis processes conducted by polymer-based anion-exchange membranes.