燃料电池用聚合物质子交换膜的研究进展

质子交换膜（PEM）是质子交换膜燃料电池的核心组件之一,具有隔绝阴阳极、提供质子传递通道和阻止燃料渗透的作用. 商业化应用的全氟磺酸PEM存在燃料渗透严重、高温条件下导电性差和成本高的问题,开发性能优良的聚合物PEM显得很有必要. 本文讨论了近年来聚合物PEM的研究进展,分别从聚合物的主链、支链和交联结构角度介绍了分子结构对薄膜相分离、质子导电性、稳定性和电池性能等性能的影响,并讨论了聚合物分子结构设计方面存在的问题,最后对燃料电池用聚合物PEM在未来的发展方向进行了展望.     

侧链磺化聚芳醚质子交换膜的研究进展

燃料电池是以氢气、甲醇等作为燃料的一种新型能量转化装置,其中质子交换膜燃料电池（Proton Exchange Membrane Fuel Cell, PEMFC）凭借其能量功率高、启动速度快和使用寿命长等优点已经在移动电源、潜艇和电动汽车等领域得到了广泛应用。质子交换膜（Proton Exchange Membrane, PEM）对PEMFC的性能影响最大,高效的PEMFC需要PEM具有高的质子电导率、良好的热稳定性和机械性能、低燃料渗透率以及优异的物理化学稳定性等。目前市面上多数使用的均是具有优异质子电导率的Nafion系列膜,但其存在制备困难、成本昂贵、质子电导率严重依赖湿度等缺点,在一定程度上限制了其发展。为了让PEM有更多的选择,科学家一直专注于使用新材料替代Nafion膜。近年来,科学家们模拟Nafion结构,通过合成各种侧链含磺酸基团的聚芳醚结构,使得亲水基团磺酸基和疏水基团之间形成微相分离结构,从而获得了一系列具有优异综合性能的PEM。本文将重点对侧链烷基磺化型、侧链磺化嵌段型、侧链局部密集磺化型、侧链磺化交联型和侧链磺化复合型这几种常见策略的合成方法及性能进行了综述,最后展望了侧链磺化聚芳醚在PEM领域的优势及发展前景。     

侧链结构对磺化聚芳醚性能及微观形貌的影响

比较了3种主链结构相同而侧链结构不同的磺化聚芳醚(SPAE)材料的性能. 分析了侧链结构对聚合物的吸水、 溶胀及质子传导行为的影响. 结果表明, 在相同的离子交换容量(IEC)条件下, 具有柔顺脂肪族侧链的聚芳醚材料具有较高的质子传导率. 其原因是由于柔顺的脂肪族侧链比刚性的芳香族侧链更易运动, 有利于侧链末端磺酸基团的聚集, 进而形成离子簇. 3种聚合物微观形貌的分析结果表明, 含柔顺侧链结构的聚合物薄膜具有更大的质子传输通道, 其结果与聚合物的宏观吸水和传导现象相吻合.     

Synthesis and properties of hydroxide conductive polymers carrying dense aromatic side-chain quaternary ammonium groups

A series of hydroxide conductive polymers QTBMs carryingdense aromatic side-chain quaternary ammonium groups has been synthesized by using a new monomer of 3,3′-di(3′′,5′′-dimethylphenyl)-4,4′-difluorodiphenyl sulfone and other commercial monomers via polycondensation reaction, and subsequent bromination, quaternization and alkalization.The chemical structures of the ionomers were confirmed by ~1H-and ~(13)C-NMR spectroscopy. Water uptake, swelling ratio, hydroxide conductivity, the number of bonded water per ammonium group(λ), volumetric ion exchange capacity(IEC_(Vwet)), mechanical and thermal properties, and chemical stability were systematically evaluated for the series of QTBMs membranes. QTBMs showed IECs ranging from1.02 meq·g~(-1)to 2.11 meq·g~(-1); in particular, QTBM-60 membrane with the highest IEC(2.11 meq·g~(-1)) had very high hydroxide ion conductivity of 131.9 m S·cm~(-1) at 80 °C, which was attributed to the well assembled nano-channels with distinct phase separation evidenced by small-angle X-ray scattering(SAXS). It was found that the hydrated QTBMs membranes were mechanically stable with moderate water uptakes and swelling ratios, high chemical stability under the harsh alkaline conditions. This work provides a facile way to prepare anion exchange membranes(AEMs) with high performances for the application in alkaline fuel cells.     

高性能氢化星型聚(苯乙烯-b-丁二烯-b-苯乙烯)嵌段共聚物阴离子交换膜的制备、结构与性能

利用常压催化加氢法合成氢化星型聚(苯乙烯-b-丁二烯-b-苯乙烯)嵌段共聚物(HSBS),依次通过氯甲基化、季铵化和碱化反应,制备两种综合性能良好的碱性阴离子交换膜(AEMs),HSBS4303-OH和HSBS4402-OH(二者制备原料中苯乙烯质量分数分别为30%和40%)。 采用傅里叶变换红外光谱(FTIR)对AEMs的结构和制备过程进行表征,并对膜的离子电导率、吸水率、溶胀度、机械性能、微相结构和耐碱稳定性等进行系统地研究。 结果表明,HSBS在90 ℃左右出现了对应于结晶结构的特征熔融峰,相较于SBS,其机械性能及尺寸稳定性显著提高。 两种AEMs中,HSBS4402-OH的性能最佳,该膜的离子交换容量为1.99 mmol/g,30 ℃时的吸水率和溶胀度分别为27.65%和5.12%,80 ℃下的离子电导率高达86.8 mS/cm。 在60 ℃下,采用2 mol/L NaOH溶液浸泡432 h后,该膜的离子电导率损失仅为8.3%。 显而易见,本文方法能为碱性阴离子交换膜燃料电池提供很有前途的AEMs。     

Comb‐shaped guanidinium functionalized poly(ether sulfone)s for anion exchange membranes: Effects of the spacer types and lengths

A series of poly(ether sulfone)‐based anion exchange membranes (AEMs), tethering with guanidinium side chains with different spacers, were synthesized via azide‐alkyne cycloaddition, deprotection, and the subsequent ion exchange reactions. The designed polymer structures were verified by the ¹H NMR spectra. Because of the appropriate water uptake and formation of interconnected ionic clusters, the GPES‐3C with propyl spacer showed higher conductivity than the GPES‐1C and GPES‐9C, with methylene and nonyl spacers, respectively. Comparatively, the GPES‐EO AEM with two ethylene oxide (EO) spacers exhibited even higher conductivity, these can be interpreted by interconnectivity of ionic channels and hydrophilicity nature of the EO spacer. Additionally, although the GPES membranes displayed sufficient thermal stability, the chemical stability of as‐prepared materials needs to be much improved for fuel cell applications. Overall, these results demonstrated that the properties of “pendent‐type” AEM can be tuned facilely by the spacer types and lengths. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1313–1321     

Improving the conductivity and dimensional stability of anion exchange membranes by grafting of quaternized dendrons

High conductivity is critical for the practical applications of anion exchange membranes (AEMs) in fuel cells. In this study, a new strategy for enhanced conductivity and dimensional stability of AEMs by incorporating quaternized dendrons is proposed. Thanks to the introduced quaternized dendrons, distinct nanoscale phase separation and well-connected ion conductive channels are formed in the as-prepared membranes (PPO-QG-x). As a result, PPO-QG-x AEMs achieve high hydroxide conductivities up to 65.5 mS cm⁻¹ at 20 °C and 121.5 mS cm⁻¹ at 80 °C (IEC = 1.95 mmol g⁻¹), while possessing good dimensional stability. Meanwhile, PPO-QG-x AEMs show good alkaline stability with the maximum loss in conductivity of 15.1% after treated in 2 M NaOH at 80 °C for 960 h. In addition, the single-cell assembled with PPO-QG-12 membrane exhibit a peak power density of 249.4 mW cm⁻² at 60 °C. Overall, this work provides a new insight to achieve high conductivity of AEMs.     

Polymers with Tethered Anionic and Cationic Groups as Membranes for Fuel Cells

Ionic clustering, water binding, and ion conductivity were studied in polymers functionalized with sulfonic acid and quaternary ammonium hydroxide groups. Small-angle x-ray scattering showed that no clustering occurred in the quaternary ammonium containing anion exchange membranes, while evidence of ionic clusters was present in both sulfonated poly(phenylene) and in Nafion, a poly(perfluorosulfonic acid). Interestingly, the water self-diffusion coefficients of the anion exchange membranes were generally greater than those observed for the sulfonated poly- (phenylene)s, and moreover, the water self diffusion coefficients in anion exchange membranes were not a strong function of diffusion time. The water binding behavior lead to increased normalized conductivity in anion exchange membranes as compared to proton exchange membranes at the highest ion exchange capacities.     

Synthesis and properties of polyimide ionomers containing sulfoalkoxy and fluorenyl groups

A series of sulfopropylated and sulfobutylated polyimide copolymers containing fluorenyl groups, SPI‐4, were synthesized to investigate the effect of alkyl side chains on the properties (stability, mechanical strength, water uptake, and proton conductivity) of the polymimide electrolyte membranes. SPI‐4 showed much better hydrolytic stability (in 10% MeOH aq at 100 °C) than the main chain sulfonated polyimide, SPI‐1. Tough, flexible, and ductile membranes were obtained from these copolymers. At high relative humidity all the SPI‐4 membranes showed high mechanical properties (>34 MPa of the maximum stress) and proton conductivity (>0.1 Scm^?1). These properties are comparable to or even better than those of the perfluorosulfonic acid ionomer (Nafion 112). The new polyimide ionomers have proved to be a possible candidate as polymer electrolyte membrane for PEFCs and DMFCs. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4439–4445, 2005     

The impact of alkyl tri‐methyl ammonium side chains on perfluorinated ionic membranes for electrochemical applications

Three different perfluorinated type polymers as anion exchange membranes for electrochemical applications were studied. They have a sulfonamide linkage to a spacer methylene chain attached to a tri‐methyl ammonium cation, specifically using a three carbon spacer chain (PFAEM_H_C3), and methylated imide polymers with three (PFAEM_CH3_C3) and six carbon spacer chain (PFAEM_CH3_C6). There are significant number of zwitterionic side chains in the PFAEM_H_C3 polymer and very few in the PFAEM_CH3_C3 or the PFAEM_CH3_C6 polymer. They have similar halide conductivity, but the PFAEM_CH3_C6 showed highest OH^? conductivity, 122 mS cm^?1 at 80 °C and 95% RH. The larger spacer chain polymer, PFAEM_CH3_C6 has a higher water uptake value (λ = 9) compared to PFAEM_CH3_C3(λ = 7) at 60 °C and 95% RH in the Cl^? form. Therefore, it has a larger domain spacing of 4.9 nm versus 4.1 nm from small angle X‐ray scattering data. The polymer was characterized by FTIR and DFT was used to fully assign the spectra. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 700–712     

高支化梳型聚芳醚砜/咪唑鎓盐功能化氧化石墨烯阴离子交换复合膜的制备与性能

通过Williamson反应, 在羟基化氧化石墨烯(GO-OH)表面修饰1-(6-溴己基)-3-甲基咪唑溴化物(6BrIm), 合成了1-(6-溴己基)-3-甲基咪唑溴化物功能化氧化石墨烯(6BrIm-GO). 将6BrIm-GO引入高支化梳型聚芳醚砜(ImHBPES-8)基体中, 经物理共混、 浇铸成膜及离子交换, 制备了一系列阴离子交换纳米复合膜(ImHBPES-8/x-6BrIm-GO). 6BrIm-GO的引入, 既作为一种功能纳米填料, 又提供了更多OH ^-离子传输位点, 在提高ImHBPES-8膜机械强度的同时保证了离子电导率. 研究了引入6BrIm-GO的含量对ImHBPES-8膜结构与性能的影响. 研究结果表明, 引入6BrIm-GO后, ImHBPES-8膜整体性能均得到改善. 当6BrIm-GO含量为0.75%时, ImHBPES-8/0.75%-6BrIm-GO复合膜的综合性能最佳, 其拉伸强度为18.32 MPa, 与ImHBPES-8膜相比, 提高了22.9%; 80 ℃下OH ^-离子电导率最高达79.8 mS/cm. 将ImHBPES-8/0.75%-6BrIm-GO复合膜浸泡在60 ℃的1 mol/L KOH溶液中进行碱稳定性测试, 300 h后离子电导率保留在初始的70%以上, 远高于ImHBPES-8膜(56%), 表明ImHBPES-8/0.75%-6BrIm-GO复合膜具有良好的耐碱稳定性. ImHBPES-8/0.75%-6BrIm-GO复合膜整体性能优异, 有望应用于碱性聚电解质燃料电池中.     

Highly Conductive Anion‐Exchange Membranes from Microporous Tröger's Base Polymers

The development of polymeric anion‐exchange membranes (AEMs) combining high ion conductivity and long‐term stability is a major challenge for materials chemistry. AEMs with regularly distributed fixed cationic groups, based on the formation of microporous polymers containing the V‐shape rigid Tröger's base units, are reported for the first time. Despite their simple preparation, which involves only two synthetic steps using commercially available precursors, the polymers provide AEMs with exceptional hydroxide conductivity at relatively low ion‐exchange capacity, as well as a high swelling resistance and chemical stability. An unprecedented hydroxide conductivity of 164.4 mS cm^?1 is obtained at a relatively a low ion‐exchange capacity of 0.82 mmol g^?1 under optimal operating conditions. The exceptional anion conductivity appears related to the intrinsic microporosity of the charged polymer matrix, which facilitates rapid anion transport.     

Diaxial diureido decalins as compact, efficient, and tunable anion transporters

Decalins bearing two axial -NHCONHAr substituents and an ester-linked alkyl side chain have been synthesized and studied as anion receptors and transporters. The design relates to steroid-based "cholapods" but is more compact and less intrinsically lipophilic. Transport rates depend on both NHAr and the alkyl side chain. High activities can be achieved; with optimal substitution, chloride-nitrate exchange across vesicle membranes is measurable at transporter/lipid ratios as low as 1:250,000.     

用于碱性膜燃料电池的新型聚苯醚阴离子交换膜的制备与性能

以2,6-二甲基聚苯醚(PPO)为原料, 经溴代及N-甲基咪唑季铵化反应, 制备了N-甲基咪唑季铵化PPO, 并进行了红外光谱(FTIR)和氢核磁共振波谱(¹H NMR)表征.所得季铵化产物与聚乙烯醇(PVA)按不同比例共混后用戊二醛交联成膜, 在碱性液中浸泡转化为OH^-型, 得到一系列阴离子交换膜.通过扫描电子显微镜(SEM) 、交流阻抗(AC)、拉伸实验和热重分析(TGA)等手段考察了膜的微观形貌及电导率、力学性能、热稳定性及耐碱性等性能.结果表明, 膜的外观形貌平整均一; 含水率为50.4%~151.2%; 溶胀度为79.2%~164.2%; 离子交换容量为0.47~1.52 mmol/g; 90℃时, M4膜的电导率高达49.1 mS/cm; 断裂伸长率达到128%, 极大改善了PPO膜应力易裂的状况.同时, N-甲基咪唑鎓基团分解温度达到170℃, 高于常用的阴离子交换膜中的季铵基团(120℃).在2 mol/L的NaOH溶液中浸泡192 h后, 电导率仅下降19%, 具备良好的耐碱性能力.     

Highly alkaline stable anion exchange membranes from nonplanar polybenzimidazole with steric hindrance backbone

The anion exchange membranes (AEMs) with both high ionic conductivity and alkali stability are always the research focus of the AEM fuel cells. Here, a novel nonplanar polymer for AEMs manufacture, mPBI‐TP‐x‐R, with excellent hydroxide stability and satisfactory processability is reported for the first time. The serial mPBI‐TP‐x resins with steric hindrance were prepared by copolymerization among 3,3′,4,4′‐tetraaminobiphenyl, isophthalic acid and tetraphenyl‐terephthalic acid (TP) in different ratios under microwave condensation. The copolymers mPBI‐TP‐x were quaternized at N1/N3‐sites of benzimidazole unit in backbone with alkyl groups (R?CH₃, C₂H₅, n‐C₃H₇, or n‐C₄H₉) to prepare soluble ionomers, and the corresponding membranes in hydroxyl ion form were prepared by a solution casting method and subsequent ion‐exchange process. The chemical structure of all membranes was characterized using FTIR and ¹H NMR spectroscopy. The properties of ion exchange capacity, water uptake, swelling ratio, tensile strength, ionic conductivity, and alkaline stability were measured. Among the prepared membranes, the mPBI‐TP‐15%‐(n‐Bu) exhibited the excellent alkaline stability (only degradation ca. 5% under 1M NaOH aqueous solution at 60 °C for 800 h) and satisfactory OH^? conductivity (46.66 mS/cm at 80 °C). The current research provides a useful exploration to commercial application of alkaline fuel cell. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1087–1096     

Novel Crosslinked Alkaline Exchange Membranes Based on Poly(phthalazinone ether ketone) for Anion Exchange Membrane Fuel Cell Applications

Novel crosslinked anion exchange membranes based on poly(phthalazinone ether ketone) (PPEK) were successfully prepared through chloromethylation, quaternization, membrane casting and OH‐ ionic exchange reaction from the quaternized PPEK (QPPEK) membrane. The quaternization was performed with N‐methylimidazolium (MIm) as ammonium agent and tetramethylethylenediamine (TMEDA) as crosslinking agent. The ion‐exchange capacity, swelling ratio (SR), water uptake (WU), and ionic conductivity of the QPPEK alkaline membranes have been systematically investigated. The results showed that QPPEK membranes have a high hydroxide conductivity and very low SR. For the QPPEK‐4 alkaline membrane with ion‐exchange capacity (IEC) 2.63 mmol/g, the WU was 35.8%, and the hydroxide conductivity was 0.028 S/cm at 30 °C and 0.032 S/cm at 70 °C, while its SR was only 7.6%. The thermal properties of the QPPEK alkaline membrane and CMPPEK were characterized using thermo‐gravimetric analysis measurements in a nitrogen atmosphere. The alkaline resistance of membrane QPPEK ?4 was also briefly investigated in 6 M KOH at 60 °C. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1632–1638     

Synthesis of ionic polybenzimidazoles with broad ion exchange capacity range for anion exchange membrane fuel cell application

In this study, new anion exchange membranes (AEM) based on crosslinked polybenzimidazole (m-PBI) with quaternary ammonium groups, crosslinkable allyl groups, and hydrophobic ethyl groups as side chains are synthesized and characterized. The AEMs are crosslinked by thermal thiol-ene reaction using a dithiol crosslinker. The ion exchange capacity (IEC) values and crosslinking density were controlled by the number of quaternary ammonium groups and allyl groups, respectively. The introduction of ethyl groups improved the solubility of ionic PBIs even at very low IEC values by eliminating the hydrogen bonding interaction of imidazole rings. This method allows ionic PBIs with broad IEC values, from 0.75 to 2.55 mmol/g, to be prepared. The broad IEC values were achieved by independently controlling the numbers of quaternary ammonium groups, allyl groups, and hydrophobic ethyl groups during preparation. The crosslinked ionic PBIs revealed hydroxide conductivity from 16 to 86 mS/cm at 80°C. The wet membranes also showed excellent mechanical strength with tensile strength of 12.2 to 20.1 MPa and Young's Modulus of 0.67 to 1.45 GPa. The hydroxide conductivity of a crosslinked membrane (0.40Q0.60Et1.00Pr, IEC = 0.95 mmol/g) decreased only 7.9% after the membranes was immersed in a 1.0 M sodium hydroxide solution at 80°C for 720 h. A single fuel cell based on this membrane showed a maximum peak power density of 136 mW/cm² with a current density of 377 mA /cm² at 60°C.     

Effect of crosslinking on the properties of partially fluorinated anion exchange membranes

A series of crosslinked, ammonium‐functionalized, and partially fluorinated copolymers have been prepared and evaluated as anion exchange membranes. In order to investigate the effect of crosslinking on the membrane properties, precursor copolymers containing chloromethyl groups were crosslinked with various aliphatic diamines followed by quaternization with monoamines. Crosslinking was effective in lowering water absorbability at no expense of high hydroxide ion conductivity of the membranes. By tuning the degree of crosslinking (20 mol %) and crosslinker chain length (C6 and C8), the highest ion conductivity of 73 mS/cm (at 80°C in water) was achieved. Furthermore, alkaline stability of the membranes was also improved by the crosslinking; the remaining ion conductivity after the stability test (in 1 M potassium hydroxide at 80°C) was 8.2 mS/cm (after 1000 h) for the C6 crosslinked membrane and 1 mS/cm (after 500 h) for the uncrosslinked membrane, respectively. The ammonium groups attached with the crosslinkers seemed more alkaline stable than the uncrosslinked benzyltrimethylammonium groups, while the polymer main chain was intact under the harsh alkaline conditions. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 1059–1069     

支化型聚苯并咪唑高温质子交换膜的制备与性能研究

通过引入1,3,5-苯三酸作为支化结构,制备了一种新型的支化型聚醚聚苯并咪唑(OPBI)高温燃料电池质子交换膜,并对支化OPBI质子交换膜的磷酸掺杂率、抗氧化稳定性、机械性能以及质子传导率等一系列性质进行了深入研究.与线型聚苯并咪唑(PBI)相比,支化OPBI具有独特的三维空间结构,极大地提高了磷酸掺杂量,随着支化度的提高,磷酸掺杂率和质子传导率随之提高.支化度为9%时,聚合物的磷酸掺杂率高达9.2 PRU?1,质子传导率达到0.0314 S/cm.此外,支化OPBI膜的溶解性较线型PBI也有较大的改善,进一步提高了聚合物的可加工性.同时,支化OPBI膜的热稳定性和抗氧化稳定性也得到了一定程度的提高,虽然机械性能略有下降,但仍能满足高温燃料电池的使用要求.     

Synthesis and characterization of bisulfonated poly(vinyl alcohol)/graphene oxide composite membranes with improved proton exchange capabilities

Composite membranes based on poly(vinyl alcohol) (PVA) and graphene oxide (GO) were prepared by solution-casting method to be used as proton exchange membranes (PEMs) in fuel cell (FC) applications. Bisulfonation was employed as a strategy to enhance the proton conductivity of these membranes. First, a direct sulfonation of the polymer matrix was accomplished by intra-sulfonation of the polymer matrix with propane sultone, followed by the inter-sulfonation of the polymer chains using sulfosuccinic acid (SSA) as a crosslinking agent. Furthermore, the addition of graphene oxide (GO) as inorganic filler was also evaluated to enhance the proton-conducting of the composite membranes. These membranes were fully characterized by scanning electron microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and tensile tests. Besides, the proton conductivity of these membranes in a fully hydrated state was also analyzed by electrochemical impedance spectroscopy (EIS). The effect of the intra- and inter-sulfonation of the polymer matrix on the structural, morphological, thermal and mechanical properties of the membranes were determined. Increasing the density of sulfonic acid groups in the membranes resulted in a trade-off between a better proton conductivity (improving from 0.26 to 1.00 mS/cm) and a decreased thermal and mechanical stability. In contrast, the incorporation of GO nanoparticles into the polymer matrix improved the thermal and mechanical stability of both bisulfonated composite membranes. The proton conductivity appreciably increased by the combination of bisulfonation and introduction of GO nanoparticles into the polymer matrix. The sPVA/30SSA/GO composite membrane exhibited a proton conductivity of 1.95 mS/cm at 25 °C. The combination of the GO nanoparticles with the chemical bisulfonation approach of PVA allows thus assembling promising proton exchange membrane candidates for fuel cell applications.