Effect of Water on the Stability of Quaternary Ammonium Groups for Anion Exchange Membrane Fuel Cell Applications
Effect of Water on the Stability of Quaternary Ammonium Groups for Anion Exchange Membrane Fuel Cell Applications
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DOI：
10.1021/acs.chemmater.7b00958
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发表时间：
2017-05-23
影响因子：
8.6
通讯作者：
Diesendruck, Charles E.
中科院分区：
文献类型：
--
作者：
Dekel, Dario R.;Amar, Michal;Diesendruck, Charles E.
在这里，我们提出了一种新的方法来测量的阴离子导电聚合物的碱性稳定性，可用作燃料电池的阴离子交换膜和阴离子交换离聚物。新的非原位技术模拟了阴离子交换膜燃料电池（AEMFC）在运行过程中的环境，其中亲核和碱性OH-物种在不存在或具有稀缺量的水的情况下，攻击离子聚合物的官能团。使用这种技术，我们清楚地显示了关键的影响。水分子的季铵（QA）阳离子的碱性稳定性通常用作功能团在AEMFC。结果表明，随着水含量的减少，QA阳离子在OH-的存在下在室温下降解得更快。随着越来越多的水分子溶解氢氧化物，其亲核性和碱性受到阻碍，QA降解显着减缓。这些结果表明，目前使用的用于测量阴离子交换膜（AEM）稳定性的碱水溶液非原位测试可能导致假阳性稳定性结果，其中阴离子传导聚合物可能看起来比它们实际上更碱稳定。
Here we present a novel methodology to measure the alkaline stability of anion conducting polymers to be used as anion exchange membranes and anion exchange ionomers for fuel cells. The new ex situ technique simulates the environment of an anion exchange membrane fuel cell (AEMFC) during operation, where nudeophilic and basic OH- species in the absence, or with a scarce amount of water, attack the functional groups of the ionic polymer. Using this technique, we clearly show the critical effect of water molecules on. the alkaline stability of quaternary ammonium (QA) cations commonly used as functional groups in AEMFCs. The results show that as the water content is reduced, the QA cations are more rapidly degraded in the presence of OH- at room temperature. With an increasing number of water molecules solvating the hydroxide, its nucleophilicity and basicity are hindered, and the QA degradation is significantly slowed. These results indicate that the currently used aqueous alkali ex situ tests to measure anion exchange membrane (AEM) stability may lead to false positive stability results where anion conducting polymers may appear more alkali stable than they really are.