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.     

磺化含酚酞侧基聚芳醚酮/氧化石墨烯复合质子交换膜的性能

采用共混制备了一系列磺化含酚酞侧基聚芳醚酮(SPEK-C)/氧化石墨烯(GO)复合质子交换膜,系统地研究了GO含量对复合膜性能的影响。结果表明,GO含量对膜的离子交换容量、稳定性、质子电导率和甲醇渗透率等有重要影响。复合膜质子电导率随GO含量增加而提高,GO含量为2%和5%的复合膜在80℃下质子电导率均在10^-1 S·cm^-1以上。80℃下,GO含量为5%的复合膜甲醇渗透率为6.69×10^-7 cm²·s^-1,低于同温度下复合前SPEK-C膜1个数量级。复合后膜的化学稳定性增强,离子交换容量和含水率均有提高,相对选择性明显增大,最高达SPEK-C的18.2倍。     

燃料电池高温质子交换膜研究进展

高温质子交换膜燃料电池具有反应动力学快、CO耐受性高等特点,但磷酸掺杂的高温质子交换膜因磷酸的流失和聚合物的降解等原因导致燃料电池的输出功率发生衰减。本文通过介绍聚苯并咪唑衍生物的高温质子交换膜、聚苯并咪唑的复合型质子交换膜、新型芳基聚合物的高温质子交换膜,阐明聚合物的主链结构、官能团结构以及复合填料对高温质子交换膜性能的影响。在近期的研究报道中,提高膜性能的主要策略包括提升自由体积、建立交联结构、嵌段共聚、复合掺杂（ILs、MOFs、PIMs、MO_x）、阳离子官能团修饰等。文章指出,在未来的研究中应该加强对磷酸基高温质子交换膜质子传输通道结构的进一步理解,关注聚合物化学降解和物理性能衰败的原因,并开发更多的新型聚合物材料。     

硫酸化SnO2/SPPESK复合质子交换膜的制备及燃料电池性能

非氟聚合物磺化聚芳醚砜酮（SPPESK）具有甲醇渗透率低、化学、热稳定性高等优点,但其高的电导率需通过提高磺化度获得,导致膜因过度溶胀而失去尺寸稳定性。添加无机纳米颗粒可以有效提高膜性能,但因其表面缺少功能化基团,导致颗粒有机相容性差,阻醇性能和质子传导率不易同时提高。硫酸化改性的纳米颗粒因其表面具有酸性位点和硫酸基团,能够有效克服这一问题。本文制备表面硫酸化改性的SnO₂（SSnO₂）纳米颗粒并引入SPPESK基质制备有机无机复合质子交换膜。当SSnO₂含量不大于7.5%时,纳米颗粒具有良好的有机相容性,可均匀分散于聚合物基质。SSnO₂含量为7.5%时,80℃下复合膜吸水率（19.6%）比SPPESK原膜提高19%,接近Nafion115。颗粒诱导膜内离子簇的聚集扩大,降低了质子的传导阻力,质子传导率分别比SPPESK原膜和Nafion115膜提高48%和30%。同时,纳米颗粒增大了甲醇传递空间位阻,甲醇渗透率较SPPESK原膜和Nafion115膜分别降低46%和71%。直接甲醇燃料电池0.5V处功率密度分别比SPPESK原膜和Nafion115膜高205%和50%。     

Sulfonated (graphene oxide/poly(ether ketone ether sulfone) (S-GO/S-PEKES) composite proton exchange membrane with high proton conductivity for direct methanol fuel cell

ABSTRACT

Sulfonated poly(ether ketone ether sulfone) (S-PEKES) was successfully prepared to obtain the currently highest degree of sulfonation of 0.744. Sulfonated graphene oxide (S-GO) was incorporated into the S-PEKES matrix to increase sulfonic groups (SO₃H) which significantly improved the proton conductivity, methanol blocking, and mechanical stability. The proton conductivity of the S-GO/S-PEKES composite membrane was enhanced up to 5.93 × 10^?2 S.cm^?1, which was 7 times higher than the commercial Nafion 117. S-GO exhibited additional positive effects namely the blocking of methanol passing through the membrane, leading to lower methanol crossover than Nafion 117 by two orders of magnitude and high mechanical stability.     

Influence of silica content in sulfonated poly(arylene ether ether ketone ketone) (SPAEEKK) hybrid membranes on properties for fuel cell application

Sulfonated poly(arylene ether ether ketone ketone) (SPAEEKK) copolymer containing pendant sulfonic acid group (sulfonic acid content (SC) = 0.67) was synthesized from commercially available monomers such as sodium 6,7-dihydroxy-2-naphthalenesulfonate (DHNS), 1,3-bis(4-fluorobenzoyl)-benzene (BFBB), and hexafluorobisphenol A (6F-BPA). SPAEEKK/silica hybrid membranes were prepared using the sol-gel process under acidic conditions. The SPAEEKK/silica hybrid membranes were fabricated with different silica contents and the membranes were modified to achieve improved proton conductivity incorporating P-OH groups (H₃PO₄ treatment).The silica particles within the membranes were used for the purpose of blocking excessive methanol cross-over and for forming a pathway for proton transport due to water absorption onto the hydrophilic SiOH surface. The proton conductivities of H₃PO₄-doped membranes were somewhat higher than the un-doped (H₃PO₄-free) membranes due to increasing hydrophilicity of the membranes. The presence of silica particles within the organic polymer matrix, which decreases the ratio of free water to bound water due to the SiOH on the surface of silica derived from sol-gel reaction, results in hybrid membranes with reduced methanol permeability and improved proton conductivity.     

sPEEK based composite membranes for direct ethanol fuel cell applications

In this paper, sulfonated poly(ether ether ketone) (sPEEK) based composite membranes are discussed. The inorganic matrix consisted of silica: Aerosil^® 380, tetraethoxysilane (TEOS), or a combination of both to obtain an interconnected silica network. The ion exchange capacity (IEC) was determined and these values coincided with the predicted IEC values. Uptake in water and 2 M ethanol was performed and an optimum was obtained. TEOS promoted the uptake due to its hydrophilicity. Proton conductivity values of the composite membranes and the polymeric reference were similar, although the IEC was lower. The stability of the composite membranes could be improved by adding an imidazole based functional silane to the composite system. This stability increased with increasing imidazole content resulting in remarkably lower ethanol permeability.     

Hydrophilic TiO2 decorated carbon nanotubes/sulfonated poly(ether ether ketone) composite proton exchange membranes for fuel cells

Sulfonated poly(ether ether ketone) (SPEEK) is currently considered to be one of the most potential candidates of commercial perfluorinated sulfonic acid proton exchange membranes. To balance the proton conductivity and mechanical properties of SPEEK, nano TiO₂ coated carbon nanotubes (TiO₂@CNTs) were prepared using a benzyl alcohol-assisted sol-gel method and then used as a new nanofiller to modify SPEEK to prepare SPEEK/TiO₂@CNTs composite membranes. The thick insulated TiO₂ coating layer can effectively avoid the risk of electronic short-circuiting formed by CNTs, while the hydrophilicity of TiO₂ can also reduce the polar difference between CNTs and SPEEK matrix, thus promoting the homogeneous dispersion of CNTs in the composites. As a result, the composite membranes demonstrated simultaneously improved strength and proton conductivity. Incorporating 5 wt% of TiO₂@CNTs exhibited 31% growth in mechanical strength when compared with pure SPEEK. Moreover, the maximum conductivity was 0.104 S cm⁻¹ (80°C) for the composite membrane with 5 wt% of TiO₂@CNTs, which was nearly twice as high as that of SPEEK membrane (0.052 S cm⁻¹).     

Proton exchange membranes based on modified sulfonated poly(ether ether ketone) membranes with chemically in situ polymerized polypyrrole

Sulfonated poly(ether ether ketone) (SPEEK) membranes were modified with chemically in situ polymerized polypyrrole (PPy). The effects of temperature and methanol concentration on the solution uptake and the swelling ratio of SPEEK/PPy membranes were investigated. The solution uptake and the swelling ratio of the membranes decreased upon the incorporation of PPy. When the methanol concentration increased, both the solution uptake and the swelling ratio increased to a maximum, and then decreased. FT-IR, XRD, DSC and TGA were used to characterize the modified membranes. The methanol permeability of modified SPEEK membranes decreased upon the incorporation of PPy, and higher selectivity values were found for SPEEK/PPy membranes in comparison with pure SPEEK and Nafion^® 117 membranes.     

Proton exchange membranes based on poly(vinylidene fluoride) and sulfonated poly(ether ether ketone)

Blend membranes were obtained by solution casting from poly(vinylidene fluoride) (PVDF) and sulfonated poly(ether ether ketone) (SPEEK) in N,N-dimethylacetamide (DMAc). DSC and XRD were used to characterize the structure of the blend membranes. The effect of PVDF content on the membrane properties was investigated. The methanol permeability, water uptake and the swelling ratio of blend membranes decreased with the increase of PVDF content. Though the proton conductivity decreased upon the addition of PVDF, they were still comparable to that of Nafion^® 117 membrane. Higher selectivities were also found for most blend membranes in comparison with Nafion^® 117 membrane. The effect of methanol concentration on solution uptake, swelling ratio and methanol permeability of the blend membranes was also studied.     

磺酸修饰的金刚石掺杂磺化聚芳醚砜质子交换膜的制备与性能

利用KMnO₄、浓H₂SO₄的氧化性及纳米金刚石边缘缺陷引入含氧官能团,得到氧化金刚石（OND）。OND在强碱条件下与1,4-丁磺酸内酯反应,进行烷基磺酸的接枝,制备带有磺酸烷基链的纳米金刚石（SND）。热重分析、红外光谱结果表明了烷基磺酸基团的成功引入,SND的离子交换容量（IEC）达到1.1mmol/g。SND与磺化聚芳醚砜（SPAES）共混后,通过溶液浇铸法制备了表面均匀平整的SPAES-SND复合膜。SPAES-SND复合膜具有较高的吸水率及较低的溶胀率、更高的氧化稳定性及电导率。其中,SPAES-SND-0.5在80℃时最高吸水率达到了75%,拉伸强度为31.3MPa,断裂伸长率为25.1%,在80℃水中的质子电导率达到166mS/cm,显示了良好的综合性能。SPAES-SND-0.5膜在80℃、100%相对湿度（RH）下燃料电池最大功率密度达到了527mW/cm²,相比于原始的SPAES膜（347mW/cm²）提高了51.9%,其优异的质子电导率和电池功率表现出较好的应用前景。     

Influence of casting conditions on the properties of sulfonated poly(ether ether ketone ketone)/phosphotungstic acid composite proton exchange membranes

The sulfonated poly(ether ether ketone ketone)/phosphotungstic acid (SPEEKK/PWA) composite membranes were researched for proton exchange membranes. The effect of casting condition on the properties of membranes was studied in detail. The study showed that the casting condition has great influence on the membrane properties because of the hydrogen bond between the SPEEK and PWA and the interaction between the SPEEKK and dimethylformamide (DMF). The PWA particles are well crystallized on the surface when the velocity of the solvent volatilization is very slow under the SEM. The study will favor further research on excellent composite membranes for proton exchange membrane fuel cells. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4020–4026, 2007     

Mass transport of direct methanol fuel cell species in sulfonated poly(ether ether ketone) membranes

Homogeneous membranes based on sulfonated poly(ether ether ketone) (sPEEK) with different sulfonation degrees (SD) were prepared and characterized. In order to perform a critical analysis of the SD effect on the polymer barrier and mass transport properties towards direct methanol fuel cell species, proton conductivity, water/methanol pervaporation and nitrogen/oxygen/carbon dioxide pressure rise method experiments are proposed. This procedure allows the evaluation of the individual permeability coefficients in hydrated sPEEK membranes with different sulfonation degrees. Nafion^® 112 was used as reference material. DMFC tests were also performed at 50 °C. It was observed that the proton conductivity and the permeability towards water, methanol, oxygen and carbon dioxide increase with the sPEEK sulfonation degree. In contrast, the SD seems to not affect the nitrogen permeability coefficient. In terms of selectivity, it was observed that the carbon dioxide/oxygen selectivity increases with the sPEEK SD. In contrast, the nitrogen/oxygen selectivity decreases. In terms of barrier properties for preventing the DMFC reactants loss, the polymer electrolyte membrane based on the sulfonated poly(ether ether ketone) with SD lower or equal to 71%, although having slightly lower proton conductivity, presented much better characteristics for fuel cell applications compared with the well known Nafion^® 112. In terms of the DMFC tests of the studied membranes at low temperature, the sPEEK membrane with SD = 71% showed to have similar performance, or even better, as that of Nafion^® 112. However, the highest DMFC overall efficiency was achieved using sPEEK membrane with SD = 52%.     

Sulfonated poly(ether ether sulfone) copolymers for proton exchange membrane fuel cells

Novel aromatic sulfonated poly(ether ether sulfone)s (SPEESs) with tert‐butyl groups were synthesized by aromatic nucleophilic polycondensation of disodium 3,3′‐disulfonate‐4,4′‐dichlorodiphenylsulfone (SDCDPS), 4,4′‐dichlorodiphenylsulfone (DCDPS), and tert‐butylhydroquinone (TBHQ). The resulting copolymers showed very good thermal stability and could be cast into tough membranes. The morphology of the membranes was investigated with atomic force microscopy. The proton conductivity of SPEES‐40 membranes increased from 0.062 S/cm at 25°C to 0.083 S/cm at 80°C, which was higher than the 0.077 S/cm of Nafion 117 under the same testing conditions. These copolymers are good candidates to be new polymeric electrolyte materials for proton exchange membrane fuel cells. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1443–1450, 2007     

质子交换膜燃料电池研究进展

质子交换膜燃料电池（proton exchange membrane fuel cell, PEMFC）因具有效率高、功率密度大、排放产物仅为水、低温启动性好等多方面优点,被公认为下一代车用动力的发展方向之一。然而,目前PEMFC在耐久性和成本方面距离商业化的要求还存在一定差距。为攻克上述两大难题,需要燃料电池全产业链的共同努力和进步。本文回顾了近年来质子交换膜燃料电池从催化剂、膜电极组件、电堆到燃料电池发动机全产业链的研究进展和成果,梳理出单原子催化剂、非贵金属催化剂、特殊形貌催化剂、有序化催化层、高温质子交换膜、膜电极层间界面优化、一体化双极板-扩散层、氢气系统循环等研究热点。文章指出,催化层低铂/非铂化、质子交换膜超薄化、膜电极组件梯度化/有序化、燃料电池运行高温化、自增湿化是未来的发展趋势,迫切需要进一步的创新与突破。     

Anisotropic membranes from electrospun mats of sulfonated/nonsulfonated poly (ether ketone)s containing ion-rich paths as proton exchange membranes

Anisotropic proton exchange membranes composed of five layers with different contents of ionic groups across the membrane were prepared by simultaneous electrospinning of sulfonated and nonsulfonated poly(ether ketone) (PEK)s. To prepare nonporous and defect- free membranes from electrospun mats, nonsulfonated fibers as hydrophobic part of the membrane were melted by hot-pressing so that covered sulfonated fibers (hydrophilic part). Prepared membranes showed better thermal and dimensional stability compared to Nafion 115. Proton conductivity of membranes was comparable with Nafion especially at higher temperatures. Water uptake of prepared membranes and mechanical strength of them were in an acceptable range. The results showed that the difference between sulfonated PEK fibers in surface and center of the membranes affect proton conductivity and mechanical properties of the membranes.     

Hydrophilic-hydrophobic multiblock copolymers based on poly(arylene ether sulfone) via low-temperature coupling reactions for proton exchange membrane fuel cells

Two series of multiblock copolymers based on poly(arylene ether sulfone)s were developed and evaluated for use as proton exchange membranes (PEMs). The multiblock copolymers were synthesized by a coupling reaction between phenoxide terminated fully disulfonated poly(arylene ether sulfone) (BPSH100) and decafluorobiphenyl (DFBP) or hexafluorobenzene (HFB) end-capped unsulfonated poly(arylene ether sulfone) (BPS0) as hydrophilic and hydrophobic blocks, respectively. The highly reactive nature of DFBP and HFB allowed the coupling reactions to be accomplished under mild reaction conditions (e.g., <105 °C). The low coupling temperatures prevented possible ether-ether exchange reactions which can cause a loss of order due to randomization of the hydrophilic-hydrophobic sequences. The multiblock copolymers produced tough and ductile membranes and their fundamental properties as PEMs were explored. They showed enhanced conductivities under fully hydrated conditions when compared with a random BPSH copolymer with a similar IEC. These copolymers also showed anisotropic swelling behavior, whereas the random copolymers were isotropic. The synthesis and fundamental properties of the multiblock copolymers are reported here and the systematic fuel cell properties and more detailed morphology characterization will be provided elsewhere.     

Effect of PES on the morphology and properties of proton conducting blends with sulfonated poly(ether ether ketone)

Development of alternate materials to Nafion, based on ionically conducting polymers and their blends is important for the wider applications of proton exchange membrane fuel cells. In this work, blends of sulfonated poly(ether ether ketone) (SPEEK) with poly(ether sulfone) (PES) are investigated. SPEEK with various ion exchange capacity (IEC) was prepared and blended with PES, which is nonionic and hydrophobic in nature. A comparative study of the water uptake, proton conductivity, and thermo‐mechanical characteristics of SPEEK and the blend membranes as a function of the IEC is presented. Addition of PES decreases the water uptake and conductivity of SPEEK. Chemical and thermal stability and mechanical properties of the membrane improve with the addition of PES. The effect of water content on the thermo‐mechanical properties of membranes was also studied. The morphology of blend membranes was studied using SEM to understand the microstructure and miscibility of the components. On the basis of the results, a plausible microstructure of the blends is presented, and is shown to be useful in understanding the variation of different properties with blending. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Montmorillonite‐reinforced sulfonated poly(phthalazinone ether sulfone ketone) nanocomposite proton exchange membranes for direct methanol fuel cells

To produce a composite membrane with high conductivity and low permeability, SPPESK with a degree of sulfonation of 101% was carefully selected for the preparation of montmorillonite (MMT)‐reinforced SPPESK using solution intercalation. The fundamental characteristics such as water uptake, swelling ratio, proton conductivity, methanol permeability, and mechanical properties of the composite membranes were studied. Water uptake is improved when organic MMT (OMMT) loading increase. The composite membranes with CTAB‐MMT loading of 4–0.5% show 0.143–0.150 S cm^?1 proton conductivity at 80°C, which approaches the value of Nafion112. In addition, methanol permeability was decreased to 6.29 × 10^?8 cm² s^?1 by the addition of 6 wt % OMMT. As a result, the SPPESK‐MMT composite membrane is a good candidate for use in direct methanol fuel cells. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39852.