A long side chain imidazolium-based graft-type anion-exchange membrane: novel electrolyte and alkaline-durable properties and structural elucidation using SANS contrast variation.,Soft Matter

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A long side chain imidazolium-based graft-type anion-exchange membrane: novel electrolyte and alkaline-durable properties and structural elucidation using SANS contrast variation.
Soft Matter ( IF 2.9 ) Pub Date : 2020-07-29 , DOI: 10.1039/d0sm00947d
Yue Zhao ₁ , Kimio Yoshimura ₁ , Ahmed Mohamed Ahmed Mahmoud ₁ , Hwan-Chul Yu ₁ , Shun Okushima ₁ , Akihiro Hiroki ₁ , Yoshihiro Kishiyama ₂ , Hideyuki Shishitani ₂ , Susumu Yamaguchi ₂ , Hirohisa Tanaka ₃ , Yohei Noda ₄ , Satoshi Koizumi ₄ , Aurel Radulescu ₅ , Yasunari Maekawa ₁

Affiliation

Newly designed styrylimidazolium-based grafted anion-exchange membranes (StIm-AEMs), in which imidazolium ionic groups are attached to styrene at the far side from the graft chains, were prepared by radiation-induced graft polymerization of p-(2-imidazoliumyl) styrene onto poly(ethylene-co-tetrafluoloethylene) (ETFE) films, followed by N-alkylation and ion-exchange reactions. StIm-AEM having an ion exchange capacity (IEC) of 0.54 mmol g⁻¹ with a grafting degree (GD) of ∼18%, possesses practical conductivity (>50 mS cm⁻¹) even with a very low water uptake (∼10%) and high stability over 600 h in a 1 M KOH solution at 80 °C. There exists a critical IEC (IEC_c) in the range of 0.7–0.8 mmol g⁻¹ over which the membrane showed high water uptake, which resulted in pronounced susceptibility to hydrolysis. Using small-angle neutron scattering technique with a contrast variation method, we found the hydrophilic phase in StIm-AEMs with IECs lower and higher than IEC_c shows “reverse-micelles” with water domains dispersed in the polymer matrix and “micelles” with graft polymer aggregates dispersed in the water matrix, respectively. The further analysis of micelle structures using the hard-sphere liquid model and Porod limit analysis reveals that the interfacial structures of ionic groups are essential for the electrochemical properties and durability of StIm-AEMs. In addition, StIm-AEM with an IEC of 0.95 mmol g⁻¹ and the maximum power density of 80 mW cm⁻² in the hydrazine hydrate fuel cell test, exhibited long-term durability under constant current (8.0 mA) up to 455 h, which, thus far, is the best durability at 80 °C for platinum-free alkaline-type liquid fuel cells.

中文翻译：

基于咪唑鎓盐的长侧链接枝型阴离子交换膜：新的电解质和耐碱特性以及使用SANS对比变化的结构解析。

通过辐射诱导的对-（2-咪唑鎓基）接枝聚合反应制备了新设计的基于苯乙烯基咪唑鎓的接枝阴离子交换膜（StIm-AEMs），其中咪唑鎓离子基团在离接枝链较远的一侧连接到苯乙烯上。苯乙烯在聚（乙烯-共-四氟乙烯）（ETFE）薄膜上，然后进行N-烷基化和离子交换反应。StIm-AEM的离子交换容量（IEC）为0.54 mmol g ^-1，接枝度（GD）为〜18％，即使吸水率很低（〜10），也具有实用的电导率（> 50 mS cm ^-1）。％）和在80°C下于1 M KOH溶液中600 h的高稳定性。存在一个关键的IEC（IEC _c）在0.7–0.8 mmol g ^-1的范围内，在该范围内膜表现出较高的吸水率，这导致明显的水解敏感性。使用小角度中子散射技术和对比度变化法，我们发现StIm-AEMs中的亲水相的IEC值低于和高于IEC _c显示“反向胶束”的水域分散在聚合物基质中，“胶束”的接枝物聚合物聚集体分别分散在水基质中。使用硬球液体模型和Porod极限分析对胶束结构进行的进一步分析表明，离子基团的界面结构对于StIm-AEM的电化学性能和耐久性至关重要。另外，IEC为0.95 mmol g ^-1的StIm-AEM在水合肼燃料电池测试中，最大功率密度为80 mW cm ^-2，在455 h下恒电流（8.0 mA）下表现出长期耐久性，这是迄今为止在80°C下的最佳耐久性无铂碱性液体燃料电池。

更新日期：2020-09-16

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