Polymer electrolyte membranes having sulfoalkyl grafts into ETFE film prepared by radiation‐induced copolymerization of methyl acrylate and methyl methacrylate

Polymer electrolyte membranes (PEMs) containing alkylsulfonic acid grafts can be prepared by radiation‐induced graft copolymerization of methyl acrylate (MA) and methyl methacrylate (MMA) into a poly(ethylene‐co‐tetrafluoroethylene) film followed by sulfonation of the MA units in the copolymer grafts using an equimolar complex of chlorosulfonic acid and 1,4‐dioxane (ClSO₃H‐Complex). PEMs with MA/MMA copolymer grafts that are 33%–79% MA units were prepared by preirradiation with a dose of 20 kGy and grafting in bulk comonomers at 60°C. The grafted films are treated with ClSO3H‐Complex to obtain PEMs with ion exchange capacity of 0.36‐0.81 mmol/g (sulfonation degrees of 20%–40%) and proton conductivity of 0.04‐0.065 S/cm. These values can be controlled by changing the MA content the sulfonation occurring at an α‐carbonyl carbon. The PEMs with higher MMA content showed higher durability in water (80°C) and under oxidative conditions (3% H₂O₂) at 60°C. This is because the PMMA grafts in the PEMs have no proton at an α‐carbonyl carbon, which is considered to be a trigger of the degradation of grafting polymers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

萘磺酸型磺化聚砜的制备及质子交换膜基本性能

以1,4-二氯甲氧基丁烷(BCD)为氯甲基化试剂,通过Fridel?Crafts烷基反应在双酚A型聚砜主链上引入氯甲基基团,制备氯甲基化聚砜(CPS);以2-萘酚-6,8-二磺酸钾(HNS)为小分子试剂,通过大分子反应制备了侧链含萘环的磺化芳香聚合物 PS-NS,对其结构进行了红外光谱和核磁氢谱表征,优化了反应条件。通过注膜方法制备功能聚合物质子交换膜PEMs,考察了PS-NS膜的吸水率和质子传导率。结果表明,合成反应是单分子亲核取代反应,极性大的二甲基亚砜为适宜的溶剂,在100℃下反应40 h,磺酸基团键合量可达1.51 mmol/g。由于亲水基团远离疏水主链,强化了相分离结构,使PEMs具有较好的吸水率和质子传导率,随磺酸基团含量增加,PEMs的吸水率和溶胀率增加,室温时的吸水率和质子传导率最高达21.3%和0.049 S/cm,满足燃料电池的实际应用要求,与商业化Nafion117膜的性能十分接近。     

High Performance Ion Exchange Membranes Prepared via Direct Polyacylation of Racemic and (S)‐1,1′‐Binaphthyl‐Based Cationic/Anionic Monomers

Side‐chain‐type sulfonated/quaternized aromatic polyelectrolytes with precisely controlled contents of ionized groups are successfully synthesized via direct polyacylation of sulfonated/quaternized monomers based on 2,2′‐dihydroxy‐1,1′‐binaphthyl (DHBN). Both proton exchange membranes (PEMs) and anion exchange membranes (AEMs) of the corresponding polyelectrolytes exhibit outstanding properties. Proton conductivity (116 mS cm^?1 at 30 °C) higher than Nafion 115 for the PEMs and OH^– conductivity (28.5–53.7 mS cm^?1 at 30 °C) comparable to Tokuyama A901 for the AEMs are accomplished. In addition, the AEMs can withstand 60 days’ aging in 1 mol L^?1 NaOH at 60 °C without degradation, as proved by ¹H NMR. More intriguingly, when starting from optically active (S)‐DHBN instead of racemic DHBN, an enhancement in proton conductivity of PEMs is observed for the first time, which opens a new door to optically active ion exchange membranes.     

Preparation and properties of chitosan/acidified attapulgite composite proton exchange membranes for fuel cell applications

A composite proton exchange membrane chitosan (CS)/attapulgite (ATP) was prepared with the organic–inorganic compounding of ATP and CS. The composite membranes were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), and fourier transform infrared spectroscopy (FTIR). The mechanical properties, thermal stability, water uptake, and proton conductivity of the composite membranes were fully investigated. The composite membranes exhibited an enhanced mechanical property, dimensional and thermal stability compared to CS membrane, owing to the interface interaction between ATP and CS. The maximum tensile strength of 53.1 MPa and decomposition temperature of 223.4°C was obtained, respectively. More importantly, the proton conductivity of the composite membrane is also enhanced, the composite membrane with 4 wt% ATP content (CS/ATP-4) exhibited the highest proton conductivity of 26.2 mS cm⁻¹ at 80°C with 100% relative humidity, which is 25.1% higher than pure CS membrane. These results may explore a simple and green strategy to prepare CS-based PEMs, which have a great potential in the application of proton exchange membrane fuel cells.     

Solution‐blown SPEEK/POSS nanofiber–nafion hybrid composite membranes for direct methanol fuel cells

This study aims to develop novel hybrid composite membranes (NHMs) by impregnating Nafion solution into the porous sulfonated poly(ether ether ketone)/polyhedral oligomeric silsesquioxanes (SPEEK/POSS) nanofibers (NFs). The composite membrane was prepared by solution blowing of a mixture of SPEEK/POSS solution. The characteristics of the SPEEK/POSS NFs and the NHMs, including morphology, thermal stability, and performance of membrane as PEMs, were investigated. The performance of NHMs was compared with that of Nafion117 and SPEEK/Nafion composite membranes. Results showed that the introduction of POSS improved the proton conductivity, water swelling, and methanol permeability of membranes. A maximum proton conductivity of 0.163 S cm^?1 was obtained when the POSS content was 6 wt % at 80°C, which was higher than that of Nafion117 and SPEEK/Nafion. NHMs could be used as proton exchange membranes (PEMs) for fuel cell applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42843.     

Silicate and zirconium phosphate modified Nafion/PTFE composite membranes for high temperature PEMFC

The PEMFC performance of MEAs prepared from Nafion-212 (thickness 50 μm, Du Pont Co), porous poly(tetrafluoro ethylene) (PTFE, thickness 15 ~ 18 μm) film reinforced Nafion (NF, thickness 20 ± 2 μm), silicate hybridized NF (NF-Si, thickness 21 ± 2 μm), and zirconium phosphate hybridized NF (NF-Zr, thickness 21 ± 2 μm) membranes were investigated at 110 °C/ 51.7% RH, 120 °C/ 38.2% RH, and 130 °C/ 28.6% RH. We show PEMFC performances of these MEAs decrease in the sequence of: NF-Zr> NF-Si> NF> Nafion-212. The NF, NF-Si, and NF-Zr membranes have lower membrane thickness and lower Nafion content and require less water for proton transport than Nafion-212 at temperatures above 110 °C, and thus have higher conductivity and better PEMFC performance than Nafion-212. Incorporating silicate and zirconium phosphate into NF membranes enhances water retention of membranes at temperatures above 110 °C and improves PEMFC performances. Besides enhancing water retention, incorporating zirconium phosphate into membranes also provides more routes for proton transport via H⁺ exchange between H₃ ⁺O and HPO₄-Zr- and between H₂ ⁺PO₄-Zr- and HPO₄-Zr-. Thus NF-Zr has a higher conductivity and better PEMFC performance than NF and NF-Si.     

交联质子交换膜研究进展

交联是近年来在质子交换膜改性中广泛使用的方法之一,交联可有效控制质子交换膜的水溶胀性,降低膜的甲醇渗透率.增加膜的耐久性,提高膜的力学性能等.作者对质子交换膜的交联方法进行了概述,重点分类讨论了共价交联,离子交联,矗子-共价交联和互穿结构交联,并对其研究进展进行了综述.     

The Preparation of Metal–Organic-Framework/Boron Phosphate Hybrid Materials for Improved Performances in Proton Exchange Membranes

New types of metal–organic framework based hybrid materials are designed and prepared, which involving the hybridization of various content of boron phosphate (BPO₄) with the precursor of HKUST-1. The structure of obtained HKUST-1/BPO₄ hybrid materials (HB) is fully investigated, and then applied to construct sulfonated poly (ether ether ketone) (SPEEK) based proton exchange membranes (SPEEK/HB). Owing to effective interactions between hybrid materials and SPEEK matrix, the achieved composite membranes reflect a considerable improvement in mechanical and thermal stability, oxidative stability, methanol permeation, and proton conductivity. In particular, the tensile strength of SPEEK/HB-20 composite membrane is 41.3 MPa, which is 1.5 times higher than pristine SPEEK, and the methanol permeability reduced to one-third of SPEEK at the same time. The SPEEK/HB-10 displays the highest proton conductivity of 37.4 mS cm⁻¹ at 80 °C, which is obviously higher than pristine SPEEK. These results reveal that the hybridization of HKUST-1 with BPO₄ provide a promising candidate in the modification of proton exchange membranes (PEMs), and this strategy also possess great application potential in other types of MOFs-based hybrid materials.     

金属有机框架材料中的质子传导及其在质子交换膜中的应用

质子交换膜（proton exchange membrane，PEM）是保证燃料电池安全、高效运行的关键部件。当前，Nafion及部分Nafion衍生物PEM被广泛应用于燃料电池、电解制氢、传感检测、液流电池等领域。但是，其仍存在制造成本过高、高效温度范围狭窄（\mathrm{约}\mathrm{20}~\mathrm{80}℃）等问题。近年来，部分金属有机框架材料（metal-organic frameworks，MOFs）因具有结晶性、可设计性和高比表面积等优点，作为潜在的新型质子导体，被用于修饰、改进现有高分子质子交换膜，或直接被作为主要质子传导介质制成质子交换膜，取得了一系列重要进展。本文详细介绍了在MOFs中五种质子传导的常见方式，综述了近年来国内外在高性能质子传导MOFs领域的代表性成果，总结了质子传导MOFs在质子交换膜中的三类常见应用方法，指出MOFs材料在提高PEM质子电导率、降低PEM成本、拓宽PEM高效工作区间等方面具有巨大的发展潜力。最后，本文提出现有MOFs在质子交换膜中的应用还存在稳定性、耐久性、有害物质逸出等方面的问题，这为新型MOFs质子交换膜的开发提供了参考与思路。     

Novel cross-linked membranes based on polybenzoxazine and polybenzimidazole containing 4-phenyl phthalazinone moiety for high-temperature proton exchange membrane

Here, we report a series of novel PA-doped cross-linked benzoxazine-polybenzimidazole copolymer membranes. These membranes were obtained by mixing PBI containing 4-phenyl phthalazinone moieties (PPBI) and 4-phenyl phthalazinone-based benzoxazine (Bp) in N-methyl pyrrolidone (NMP), followed by heating to 260 °C. The cross-linking reaction was determined by DSC and gel fraction tests. These copolymer membranes showed excellent comprehensive properties, with high proton conductivity up to 14.7 mS/cm at 160 °C under anhydrous conditions. Besides, the P(PBp-co-PPBI)-30 membrane exhibited excellent mechanical property (approximately 50% improvement in tensile modules and strength compared to the pristine PPBI) and oxidative stability in Fenton’s test (remaining intact after 226 h). This study proved that using benzoxazine as a cross-linking agent is a promising method for improving the properties of proton exchange membranes (PEMs).     

Preparation and properties of pore-filling membranes based on sulfonated copolyimides and porous polyimide matrix

The porous polyimide films were prepared by a wet phase inversion process. The influence of coagulating non-solvent on morphology, pore size and porosity of porous films was investigated. A series of pore-filling sulfonated polyimide (PFSPI) membranes, which derived from a homogenous spongy-like porous polyimide film as matrix filled with sulfonated copolyimides, were prepared and characterized. These PFSPI membranes exhibited excellent thermal stability with desulfonation temperature of 283–330 °C and good oxidative stability in Fenton's agent due to the protective effect of porous polyimide matrix on the sulfonic acid groups. The swelling of PFSPI membranes could be effectively suppressed by the porous matrix, which leads to the excellent dimensional stability and good water stability of membranes. The PFSPI membranes exhibited high proton conductivity at elevated temperature. All the PFSPI membranes displayed better permselectivity as compared with Nafion 115, which is attributed to their much lower methanol permeability.     

用于质子交换膜的高质子传导率聚合物研究进展

质子传导率超过Nafion膜的质子交换膜是近年来研究的焦点。质子交换膜的质子传导率与它们的IEC值和形态有关。形成离子通道是开发高质子传导率的质子交换膜的一种有效方法。形成离子通道主要有3种:1)用嵌段共聚物的微相分离;2)侧链和支链磺化的聚合物;3)局部区域的高密集磺化。此外,与无机纳米材料形成纳米复合材料的质子交换膜也能提高质子交换膜的质子传导率及质子交换膜的机械强度、尺寸稳定性、耐氧化稳定性等性能。综述了关于用于高质子传导率的燃料电池质子交换膜(PEM)的聚合物的研究进展。对高质子传导率的燃料电池膜聚合物的发展趋势进行了展望。     

Investigation on carbon nanotube oxide for anhydrous proton exchange membranes application

The widespread participation of polymers in the membrane preparation has been considering to be critical for the development of proton exchange membranes (PEMs). For the polymers without functional groups to conduct protons, the introduction of proton conduction carriers with the formation of composite membranes is an effective strategy to prepare PEMs with the outstanding proton conductivity. However, there remains a potential risk of the components leaking from composite membranes due to the lack of the interaction force. Here, the composite of carbon nanotube oxide (OCNT) assembling with cadmium telluride (CdTe) and 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF₆) was introduced into the system of phosphoric acid (PA) doping poly(vinylidene fluoride) (PVDF) with the formation of PVDF/OCNT-CdTe-bmimPF₆/85%PA membranes. PA molecules are anchored by the inorganics of OCNT-CdTe-bmimPF₆ and are stabilized in membranes. The high and stable proton conductivity values at the elevated temperature are obtained comparing the reported PVDF/bmimPF₆/PA membranes. Specifically, the proton conductivity value reached 1.28 × 10⁻¹ S/cm at 160 °C and the value is stable 1.70 × 10⁻² S/cm at 120 °C lasting for 350 h. The fine stability in components could make the membranes extricate from the predicament of proton conductivity decline exceeding 120 °C under anhydrous conditions in PVDF/bmimPF₆/PA membranes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48833.     

Stable zirconium hydrogen phosphate-silica nanocomposite membranes with high degree of bound water for fuel cells

Zirconium hydrogen phosphate (ZrP)-silica nanocomposite polymer electrolyte membranes (PEMs) were prepared by sol-gel method in aqueous media. Hydrophilic and hydrophobic regions of PEMs were tailored by molecular level of architecture to introduce proton conducting pathways and methanol impervious nature. ZrP-silica nanocomposite PEMs showed improved thermal, mechanical, oxidative and hydrolytic stabilities along with high conductivity, methanol retention capacity, which are essential requirements. Furthermore, high degree of bound water content in membrane matrix indicates suitability of reported PEMs under anhydrous or low-humidity conditions. These PEMs were well processed as self-supporting film, and exhibited high selectivity parameter in comparison to Nafion117 membrane for direct methanol fuel cell (DMFC) applications.     

新型细菌纤维素基阻醇质子交换膜的制备及表征

以凝胶贴附法,在Nation膜两侧贴附细菌纤维素（BC）膜,制备出BC／Nation／BC夹心复合膜,以期结合Nation膜的良好导电性和BC膜的优秀阻醇性,制备新型阻醇质子交换膜。利用扫描电镜、热重分析对其形态结构和热稳定性进行研究,并对夹心膜的尺寸稳定性、质子传导率和甲醇渗透率进行表征。结果发现,复合膜的夹心结构紧密,热稳定性良好,尺寸稳定性比市售的Nation膜有很大改善,提高了43％。夹心膜的质子传导率随温度的升高明显上升,虽略低于Nation膜,但是甲醇渗透率明显降低一个数量级,阻醇性能得到了很大改善。组装成电池后,单电池开路电压达到922mV,最大发电功率密度为7．2mW／cm^2。该结果表明夹心复合膜作为新型质子交换膜应用于直接甲醇燃料电池中具有很大潜力。     

Synthesis and characterization of sulfonated fluorene-containing poly(arylene ether ketone) for high temperature proton exchange membrane

A novel fluorene-containing poly(arylene ether ketone) were synthesized followed by sulfonating into a series of sulfonated fluorene-containing poly(arylene ether ketone)s using chlorosulfonic acid. The sulfonated polymers were thereafter cast into membranes from their solutions. The properties of the ionic exchange capacity, sulfonation degree, water-uptake, mechanical properties, thermal and oxidative stabilities as well as proton conductivities of the membranes were fully investigated. It was found that their proton conductivities increased continuously with increasing testing temperature up to 130 °C at 100% relative humidity. The membrane exhibited a higher proton conductivity and other comprehensive properties for proton exchange membrane than Nafion-117 at 130 °C under same testing conditions.     

Study on radiation grafting of acrylic acid onto fluorine-containing polymers. II. Properties of membrane obtained by preirradiation grafting onto poly(tetrafluoroethylene)

Some properties of the membranes obtained by the preirradiation grafting of acrylic acid onto poly(tetrafluoroethylene) (PTFE) film have been studied. The dimensional change by grafting and swelling, water uptake, electric conductivity, and mechanical properties of the grafted PTFE films were measured and were found to increase as the grafting proceeds. These properties were found to be dependent mainly on the degree of grafting regardless of grafting conditions except higher monomer concentration (80 wt %). The electric conductivity and mechanical properties of the membranes at 80 wt % monomer concentration is lower than those at a lower monomer concentration. The results suggest that the membranes obtained at 80-wt % acrylic acid solution have a somewhat heterogeneous distribution of electrolyte groups as compared with those prepared at a monomer concentration less than 60 wt %. X-ray microscopy of the grafted films revealed that the grafting begins at the part close to the film surface and proceeds into the center with progressive diffusion of monomer to give finally the homogeneous distribution of electrolyte groups. The membranes show good electrochemical and mechanical properties which make them acceptable for the practical uses as cation exchange membrane.     

Performance of the sulfonated poly ether ether ketone proton exchange membrane modified with sulfonated polystyrene and phosphotungstic acid for microbial fuel cell applications

In this research, the preparation of low cost proton exchange membranes (PEMs) based on sulfonated poly ether ether ketone (SPEEK) for application in the microbial fuel cells (MFCs) is studied. Sulfonated polystyrene (SPS) and phosphotungstic acid (PWA) were employed to improve the performance of PEM through the creation of more proton pathways. At first, the sulfonation of PEEK and polystyrene were performed through two modified methods to obtain uniform and high degree of sulfonation (DS) of the polymers and then, the PEMs were prepared through the solution casting method. Accordingly, the formation of uniform skin layer was confirmed by the SEM micrographs. Blending the aforementioned additives to the SPEEK polymer solution significantly enhanced the proton conductivity, water uptake and durability of the modified membranes. The proton conductivities of SPEEK/SPS and SPEEK/PWA membranes at additive/SPEEK weight ratio of 0.15 were 45.3% and 26.2% higher than that of the commercial Nafion117 membrane, respectively. Moreover, the degradation times for the abovementioned modified membranes were 140 and 350 min which indicated satisfactory oxidation stability. Besides, the aforementioned membranes exhibited two times more water uptake compared to the neat SPEEK membrane. Finally, SPEEK/SPS and SPEEK/PWA membranes produced 68% and 36% higher maximum power in the MFC, compared to the commercial Nafion117 membrane. Therefore, the fabricated PEMs are potentially suitable alternatives to be used in the fuel cell applications.     

Preparation and characterization of proton exchange membrane based on polyphosphoric acid modified by PVDF‐HFP

A polyphosphoric acid functionalized proton exchange membrane (PEM) was prepared by a ring opening reaction using the epoxycyclohexylethyltrimethoxysilane (EHTMS) and amino trimethylene phosphonic acid (ATMP) as raw materials and was modified by poly(vinylidene fluoride)–hexafluoro propylene (PVDF‐HFP). The structure of the membranes was characterized by Fourier transform infrared and scanning electron microscopy. The X‐ray photoelectron spectroscopy explores the content of the elements in the membrane related to the ion exchange capacity value. The membranes’ properties including water uptake, swelling ratio, proton conductivity, and hydrolysis stability were studied. Performance tests show that when ATMP/EHTMS = 1/5, conductivity of the PVDF‐HFP modified PEMs increased from 0.83 × 10^?4 S cm^?1 at 20 °C to 9.53 × 10^?3 S cm^?1 at 160 °C, the swelling ratio of membranes decreased from 2.71% to 2.13%. The results indicate that the introduction of F atoms is beneficial to increase the proton conductivity and the dimensional stability. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46737.     

Synthesis and characterization of multiblock semi-crystalline hydrophobic poly(ether ether ketone)–hydrophilic disulfonated poly(arylene ether sulfone) copolymers for proton exchange membranes

Multiblock copolymers based on alternating segments of telechelic phenoxide terminated hydrophilic fully disulfonated poly(arylene ether sulfone) (BPS100) and decafluorobiphenyl (DFBP) terminated hydrophobic poly(arylene ether ketimine) (PEEKt), were synthesized from the hydrophilic and ketimine-protected amorphous hydrophobic telechelic oligomers by nucleophilic coupling reactions. After film formation from DMSO, the copolymer was acidified, which converted the ketimine to semi-crystalline ketone segments and the sulfonate salts to disulfonic acids. A semi-crystalline phase with a T_m of 325 °C was confirmed. The semi-crystalline multiblock copolymer membranes were tough, ductile and solvent resistant. Fundamental properties as proton exchange membranes (PEMs) showed enhanced conductivities under fully hydrated and reduced humidity conditions. These multiblock copolymers exhibited low in-plane anisotropic swelling behavior, in contrast to the random copolymers.