logo

Chinese Science Bulletin, Volume 64, Issue 2: 145-152(2019) https://doi.org/10.1360/N972018-00770

Alkali stability of anion exchange membrane

More info
  • ReceivedJul 31, 2018
  • AcceptedOct 26, 2018
  • PublishedDec 21, 2018

Abstract

Anion exchange membrane fuel cells (AEMFCs) are attractive alternatives to proton exchange membrane fuel cells due to using non-noble metal catalysts and faster cathode reaction kinetics. Anion exchange membranes (AEMs) are one of the key materials composed of AEMFCs. The hydroxide conductivity of AEMs has been able to meet operating requirements of fuel cells. Although the hydroxide conductivity is no longer a problem, the stability of AEMs is still a notable challenge. This work mainly introduces the development of alkaline stability of AEMs.

AEMs mainly consist of functional groups, side chains and polymer backbones. The degradation of functional groups causes by attacking of hydroxide ion through Hofmann elimination, nucleophilic substitution and ylide-intermediate degradation pathways. Numerous functional groups have been developed in order to improve the alkaline stability of AEMs. The introductions of appropriate electron donors and steric shielding are effective ways to weaken the attack of hydroxide ion. Developing new functional groups is a very important way. In addition, the development of novel stable groups is an important way for long-lived AEMs. For example, hetero-cycloaliphatic quaternary ammonium cations (QAs) are proved to be especially stable in both model compound studies and even AEM studies.

The most commonly studied AEMs were synthesized by chloromethylation/bromination of the aromatic backbones, followed by a Menshutkin reaction to introduce QAs. Benzylic groups, electron-withdrawing groups, are prone to degrade by nucleophilic substitution on the benzylic carbon/α-carbon, Hofmann elimination and N-ylide intermediate formation in the presence of hydroxide ion. Therefore, the tethering linkage between the polymer backbone and functional groups is quite important. Recent studies have mainly introduced long side chains between functional groups and polymer backbones, leaving functional groups away from the benzene ring of the polymer backbone. The all-alkyl, amine- and ether-containing branched-chain structures are proved to be stable.

Poly(arylene ether)s have been extensively studied in AEMs due to the advantages of good thermal stability, high mechanical property and easy modification. Frequently employed polyaromatic electrolytes are quaternized poly(aryl ether sulfone)s, which are prepared via the nucleophilic polycondensation reaction. The introduction of functional groups leads to degrade of these main chains containing aryl ether bonds, which are unable to avoid in the polycondensation reaction. It is necessary that main chains are devoid of aryl ether bonds so as to develop AEMs with excellent alkaline stability. Diels-Alder reaction, coupling reaction and acid-catalyzed Friedel-Craft polycondensation are effective methods for synthesizing aromatic backbones devoid of aryl ether bonds. In addition, aliphatic backbones, such as poly(ethylene-co-tetrafluoroethylene), are proved to have good stability in alkaline conditions, so its modification for AEMs has also become an important research direction.

At present, the alkaline stability of AEMs has made great progress. Three major aspects have been studied in an effort to develop stable AEMs: (1) screening stable functional groups such as five- or six-membered cyclic amines, substituted imidazoles; (2) developing effective linkages between functional groups and polymer backbones; (3) designing aryl ether-free aromatic backbones and stable aliphatic backbones. The designed AEMs can remain for hundreds of hours without degradation in alkaline solution, which is a significant advancement in increasing alkaline stability of AEMs.


Funded by

国家重点研发计划(2016YFB0101203)

国家自然科学基金(21406031)

国家自然科学基金(U1663223)

中央高校基本科研业务费(DUT18JC40)

辽宁省科学技术计划(201601037)


References

[1] Liu J G, Sun G Q. A survey of fuel cells (in Chinese). Physics, 2004, 33: 70–84 [刘建国, 孙公权. 燃料电池概述. 物理, 2004, 33: 70–84]. Google Scholar

[2] Yu H M, Yi B L. Current status of vehicle fuel cells and electrocatalysis (in Chinese). Sci Sin Chim, 2012, 42: 480-494 CrossRef Google Scholar

[3] Zhuang L. Alkaline polymer electrolyte fuel cells completely free from noble metal catalysts (in Chinese). China Basic Sci, 2009, 6: 28–29 [庄林. 完全不使用贵金属催化剂的聚合物电解质燃料电池. 中国基础科学, 2009, 6: 28–29]. Google Scholar

[4] Couture G, Alaaeddine A, Boschet F, et al. Polymeric materials as anion-exchange membranes for alkaline fuel cells. Prog Polymer Sci, 2011, 36: 1521-1557 CrossRef Google Scholar

[5] Shin D W, Guiver M D, Lee Y M. Hydrocarbon-based polymer electrolyte membranes: Importance of morphology on ion transport and membrane stability. Chem Rev, 2017, 117: 4759-4805 CrossRef Google Scholar

[6] Gottesfeld S, Dekel D R, Page M, et al. Anion exchange membrane fuel cells: Current status and remaining challenges. J Power Sources, 2018, 375: 170-184 CrossRef ADS Google Scholar

[7] Arges C G, Zhang L. Anion Exchange Membranes' Evolution toward High Hydroxide Ion Conductivity and Alkaline Resiliency. ACS Appl Energy Mater, 2018, 1: 2991-3012 CrossRef Google Scholar

[8] Ge Q, Ran J, Miao J, et al. Click chemistry finds its way in constructing an ionic highway in anion-exchange membrane. ACS Appl Mater Interfaces, 2015, 7: 28545-28553 CrossRef Google Scholar

[9] He S, Liu L, Wang X, et al. Azide-assisted self-crosslinking of highly ion conductive anion exchange membranes. J Membrane Sci, 2016, 509: 48-56 CrossRef Google Scholar

[10] Dong X, Xue B, Qian H, et al. Novel quaternary ammonium microblock poly (p-phenylene-co-aryl ether ketone)s as anion exchange membranes for alkaline fuel cells. J Power Sources, 2017, 342: 605-615 CrossRef ADS Google Scholar

[11] Wu X, Chen W, Yan X, et al. Enhancement of hydroxide conductivity by the di-quaternization strategy for poly(ether ether ketone) based anion exchange membranes. J Mater Chem A, 2014, 2: 12222-12231 CrossRef Google Scholar

[12] Chen W, Hu M, Wang H, et al. Dimensionally stable hexamethylenetetramine functionalized polysulfone anion exchange membranes. J Mater Chem A, 2017, 5: 15038-15047 CrossRef Google Scholar

[13] Li X, Yu Y, Liu Q, et al. Synthesis and characterization of anion exchange membranes based on poly(arylene ether sulfone)s containing various cations functioned tetraphenyl methane moieties. Int J Hydrogen Energy, 2013, 38: 11067-11073 CrossRef Google Scholar

[14] Pan J, Chen C, Li Y, et al. Constructing ionic highway in alkaline polymer electrolytes. Energy Environ Sci, 2014, 7: 354-360 CrossRef Google Scholar

[15] Hugar K M, Kostalik Iv H A, Coates G W. Imidazolium Cations with Exceptional Alkaline Stability: A Systematic Study of Structure–Stability Relationships. J Am Chem Soc, 2015, 137: 8730-8737 CrossRef Google Scholar

[16] Liu Y, Wang J, Yang Y, et al. Anion transport in a chemically stable, sterically bulky α-C modified imidazolium functionalized anion exchange membrane. J Phys Chem C, 2014, 118: 15136-15145 CrossRef Google Scholar

[17] Wang J, Wei H, Yang S, et al. Constructing pendent imidazolium-based poly(phenylene oxide)s for anion exchange membranes using a click reaction. RSC Adv, 2015, 5: 93415-93422 CrossRef Google Scholar

[18] Si Z, Sun Z, Gu F, et al. Alkaline stable imidazolium-based ionomers containing poly(arylene ether sulfone) side chains for alkaline anion exchange membranes. J Mater Chem A, 2014, 2: 4413-4421 CrossRef Google Scholar

[19] Wang J, Li S, Zhang S. Novel hydroxide-conducting polyelectrolyte composed of an poly(arylene ether sulfone) containing pendant quaternary guanidinium groups for alkaline fuel cell applications. Macromolecules, 2010, 43: 3890-3896 CrossRef ADS Google Scholar

[20] Cheng J, Yang G, Zhang K, et al. Guanidimidazole-quanternized and cross-linked alkaline polymer electrolyte membrane for fuel cell application. J Membrane Sci, 2016, 501: 100-108 CrossRef Google Scholar

[21] Qu C, Zhang H, Zhang F, et al. A high-performance anion exchange membrane based on bi-guanidinium bridged polysilsesquioxane for alkaline fuel cell application. J Mater Chem, 2012, 22: 8203-8207 CrossRef Google Scholar

[22] Gu S, Cai R, Luo T, et al. A soluble and highly conductive ionomer for high-performance hydroxide exchange membrane fuel cells. Angew Chem Int Ed, 2009, 48: 6499-6502 CrossRef Google Scholar

[23] Zhang B, Gu S, Wang J, et al. Tertiary sulfonium as a cationic functional group for hydroxide exchange membranes. RSC Adv, 2012, 2: 12683-12685 CrossRef Google Scholar

[24] Gu S, Wang J, Kaspar R B, et al. Permethyl cobaltocenium (Cp*2Co+) as an ultra-stable cation for polymer hydroxide-exchange membranes. Sci Rep, 2015, 5: 11668 CrossRef ADS Google Scholar

[25] Zha Y, Disabb-Miller M L, Johnson Z D, et al. Metal-cation-based anion exchange membranes. J Am Chem Soc, 2012, 134: 4493-4496 CrossRef Google Scholar

[26] Ge X, He Y, Guiver M D, et al. Alkaline anion-exchange membranes containing mobile ion shuttles. Adv Mater, 2016, 28: 3467-3472 CrossRef Google Scholar

[27] Si Z, Qiu L, Dong H, et al. Effects of substituents and substitution positions on alkaline stability of imidazolium cations and their corresponding anion-exchange membranes. ACS Appl Mater Interfaces, 2014, 6: 4346-4355 CrossRef Google Scholar

[28] Wright A G, Weissbach T, Holdcroft S. Poly(phenylene) and m-Terphenyl as Powerful Protecting Groups for the Preparation of Stable Organic Hydroxides. Angew Chem Int Ed, 2016, 55: 4818-4821 CrossRef Google Scholar

[29] Marino M G, Kreuer K D. Alkaline stability of quaternary ammonium cations for alkaline fuel cell membranes and ionic liquids. ChemSusChem, 2015, 8: 513-523 CrossRef Google Scholar

[30] Dang H S, Jannasch P. A comparative study of anion-exchange membranes tethered with different hetero-cycloaliphatic quaternary ammonium hydroxides. J Mater Chem A, 2017, 5: 21965-21978 CrossRef Google Scholar

[31] Pan Y, Zhang Q, Yan X, et al. Hydrophilic side chain assisting continuous ion-conducting channels for anion exchange membranes. J Membrane Sci, 2018, 552: 286-294 CrossRef Google Scholar

[32] Yan X, Deng R, Pan Y, et al. Improvement of alkaline stability for hydroxide exchange membranes by the interactions between strongly polar nitrile groups and functional cations. J Membrane Sci, 2017, 533: 121-129 CrossRef Google Scholar

[33] Gao L, He G, Pan Y, et al. Poly(2,6-dimethyl-1,4-phenylene oxide) containing imidazolium-terminated long side chains as hydroxide exchange membranes with improved conductivity. J Membrane Sci, 2016, 518: 159-167 CrossRef Google Scholar

[34] Yan X, Gao L, Zheng W, et al. Long-spacer-chain imidazolium functionalized poly(ether ether ketone) as hydroxide exchange membrane for fuel cell. Int J Hydrogen Energy, 2016, 41: 14982-14990 CrossRef Google Scholar

[35] Gong X, Yan X, Li T, et al. Design of pendent imidazolium side chain with flexible ether-containing spacer for alkaline anion exchange membrane. J Membrane Sci, 2017, 523: 216-224 CrossRef Google Scholar

[36] Hou J, Wang X, Liu Y, et al. Wittig reaction constructed an alkaline stable anion exchange membrane. J Membrane Sci, 2016, 518: 282-288 CrossRef Google Scholar

[37] Dang H S, Jannasch P. Exploring different cationic alkyl side chain designs for enhanced alkaline stability and hydroxide ion conductivity of anion-exchange membranes. Macromolecules, 2015, 48: 5742-5751 CrossRef ADS Google Scholar

[38] Lin B, Qiu L, Qiu B, et al. A soluble and conductive polyfluorene ionomer with pendant imidazolium groups for alkaline fuel cell applications. Macromolecules, 2011, 44: 9642-9649 CrossRef ADS Google Scholar

[39] You W, Hugar K M, Coates G W. Synthesis of alkaline anion exchange membranes with chemically stable imidazolium cations: Unexpected cross-linked macrocycles from ring-fused romp monomers. Macromolecules, 2018, 51: 3212-3218 CrossRef ADS Google Scholar

[40] Zhuo Y Z, Lai A L, Zhang Q G, et al. Enhancement of hydroxide conductivity by grafting flexible pendant imidazolium groups into poly(arylene ether sulfone) as anion exchange membranes. J Mater Chem A, 2015, 3: 18105-18114 CrossRef Google Scholar

[41] Fujimoto C, Kim D S, Hibbs M, et al. Backbone stability of quaternized polyaromatics for alkaline membrane fuel cells. J Membrane Sci, 2012, 423-424: 438-449 CrossRef Google Scholar

[42] Arges C G, Ramani V. Two-dimensional NMR spectroscopy reveals cation-triggered backbone degradation in polysulfone-based anion exchange membranes. Proc Natl Acad Sci USA, 2013, 110: 2490-2495 CrossRef ADS Google Scholar

[43] Mohanty A D, Tignor S E, Krause J A, et al. Systematic alkaline stability study of polymer backbones for anion exchange membrane applications. Macromolecules, 2016, 49: 3361-3372 CrossRef ADS Google Scholar

[44] Miyanishi S, Yamaguchi T. Ether cleavage-triggered degradation of benzyl alkylammonium cations for polyethersulfone anion exchange membranes. Phys Chem Chem Phys, 2016, 18: 12009-12023 CrossRef ADS Google Scholar

[45] Hibbs M R. Alkaline stability of poly(phenylene)-based anion exchange membranes with various cations. J Polym Sci Part B-Polym Phys, 2013, 51: 1736-1742 CrossRef ADS Google Scholar

[46] Fan J, Wright A G, Britton B, et al. Cationic Polyelectrolytes, Stable in 10 M KOHaq at 100 °C. ACS Macro Lett, 2017, 6: 1089-1093 CrossRef Google Scholar

[47] Lee W H, Kim Y S, Bae C. Robust hydroxide ion conducting poly(biphenyl alkylene)s for alkaline fuel cell membranes. ACS Macro Lett, 2015, 4: 814-818 CrossRef Google Scholar

[48] Lee W H, Mohanty A D, Bae C. Fluorene-based hydroxide ion conducting polymers for chemically stable anion exchange membrane fuel cells. ACS Macro Lett, 2015, 4: 453-457 CrossRef Google Scholar

[49] Pham T H, Olsson J S, Jannasch P. N-Spirocyclic Quaternary Ammonium Ionenes for Anion-Exchange Membranes. J Am Chem Soc, 2017, 139: 2888-2891 CrossRef Google Scholar

[50] Olsson J S, Pham T H, Jannasch P. Poly(arylene piperidinium) hydroxide ion exchange membranes: Synthesis, alkaline stability, and conductivity. Adv Funct Mater, 2018, 28: 1702758 CrossRef Google Scholar

[51] Ponce-González J, Whelligan D K, Wang L Q, et al. High performance aliphatic-heterocyclic benzyl-quaternary ammonium radiation- grafted anion-exchange membranes. Energy Environ Sci, 2016, 9: 3724–3735. Google Scholar

[52] Noonan K J T, Hugar K M, Kostalik Iv H A, et al. Phosphonium-functionalized polyethylene: A new class of base-stable alkaline anion exchange membranes. J Am Chem Soc, 2012, 134: 18161-18164 CrossRef Google Scholar

[53] Zhu T, Xu S, Rahman A, et al. Cationic metallo-polyelectrolytes for robust alkaline anion-exchange membranes. Angew Chem Int Ed, 2018, 57: 2388-2392 CrossRef Google Scholar

[54] Liu X, Gao H, Chen X, et al. Poly(tetrafluoroethylene-co-perfluorovinyl ether sulfonamide) for anion exchange membranes. Polym Chem, 2016, 7: 2904-2912 CrossRef Google Scholar

[55] Olsson J S, Pham T H, Jannasch P. Poly( N , N-diallylazacycloalkane)s for Anion-Exchange Membranes Functionalized with N-Spirocyclic Quaternary Ammonium Cations. Macromolecules, 2017, 50: 2784-2793 CrossRef ADS Google Scholar

  • Figure 1

    Functional groups for anion exchange membranes. (1) Quaternary ammonium; (2) DABCO based ammonium; (3) imidazolium; (4) benzimidazolium; (5) guanidium; (6) hexamethylenetetrammonium; (7) pyridinium; (8) pyrrolidinium; (9) permethyl cobaltocenium; (10) piperidinium; (11) morpholinium; (12) piperazinium; (13) quinuclidium; (14) azepanium; (15) 6-azonia-spiro[5.5]undecane based ammonium; (16) methoxy- substituted triarylsulfonium; (17) tris(2,4,6-trimethoxyphenyl) phosphonium; (18) bis(terpyridine)ruthenium(II)

  • Figure 2

    Chemical structures of branched AEMs

  • Figure 3

    Chemical structures of aryl ether-free polymer based AEMs

Copyright 2020 Science China Press Co., Ltd. 《中国科学》杂志社有限责任公司 版权所有

京ICP备18024590号-1