Practical implementation of bis-six-membered N-cyclic quaternary ammonium cations in advanced anion exchange membranes for fuel cells: Synthesis and durability
Practical implementation of bis-six-membered N-cyclic quaternary ammonium cations in advanced anion exchange membranes for fuel cells: Synthesis and durability
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DOI：
10.1016/j.memsci.2019.02.051
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发表时间：
2019-05-15
影响因子：
9.5
通讯作者：
Li, Nanwen
中科院分区：
文献类型：
--
作者：
Chu, Xiaomeng;Liu, Lei;Li, Nanwen
介绍了N-环季铵(QA)阴离子交换膜在碱性燃料电池中的实际应用。PPO主链上结合了两种QA，包括六元(DMP)和双六元N-环QA(ASU)。由于更发达的微相分离，环尺寸较大的PPO-ASU膜在80℃时表现出最高的氢氧化物电导率，为76.5ms cm(-1)。不幸的是，含有N-环QA阳离子的AEMS在80℃的10M NaOH中储存250h后，PPO-ASU膜发生了化学降解，离子电导率损失了45%，对这些AEMS的后分析表明，Hoffmann消除和SN2取代开环是AEMS的主要降解机理，与模型化合物的结果一致。在60℃下，基于ASU的AEMS在单个H-2/O-2燃料电池中的最大功率密度为124.7mWcm(-2)。然而，使用AEMS的燃料电池的耐久性测试表明，在0.3V工作40h后，性能损失了90%。进一步的核磁共振分析表明，Sn2取代引发的开环是AEMS退化的主要途径，导致燃料电池的耐久性不佳。这些发现比较了AEMS在原位和非原位的稳定性，为未来发展先进的AEMS提供了一些启示。
Practical implementation of anion exchange membranes (AEMs) having N-cyclic quaternary ammonium (QA) in alkaline fuel cells is demonstrated. Two kinds of QAs are incorporated along PPO backbone, including six-membered (DMP) and bis-six-membered N-cyclic QA (ASU). PPO-ASU membranes with bulky ring size display the highest hydroxide conductivity of 76.5 mS cm(-1) at 80 degrees C, due to more developed microphase separation. Unfortunately, AEMs with N-cyclic QA cations undergo chemical degradation with>45% ionic conductivity loss for PPO-ASU membrane after storage in 10M NaOH at 80 degrees C for 250 h. Post-analysis of these AEMs reveals that Hoffmann elimination and ring-opening by SN2 substitution are the dominant degradation mechanisms, which is in agreement with the results for model compounds. ASU-based AEMs exhibit a maximum power density of 124.7mWcm(-2) in a single H-2/O-2 fuel cell at 60 degrees C. However, durability testing of fuel cell with the AEMs shows a 90% performance loss after operating at 0.3 V for 40 h. Further NMR analysis suggests that SN2 substitution triggered ring-opening is the dominant pathway for the degradation of AEMs, leading to the unsatisfactory fuel cell durability. These findings that compare the in situ and ex situ stability of AEMs give some insights on future directions for developing advanced AEMs.