Yuan Zhizhang, Li Xianfeng, Zhao Yuyue, Zhang Huamin
Division of Energy Storage, Dalian Institute of Chemical Physics, Chinese Academy of Sciences , 457 Zhongshan Road, Dalian 116023, P. R. China.
Graduate School of Chinese Academy of Sciences , Beijing 100039, P. R. China.
ACS Appl Mater Interfaces. 2015 Sep 2;7(34):19446-54. doi: 10.1021/acsami.5b05840. Epub 2015 Aug 24.
The stability of hydrocarbon ion exchange membranes is one of the critical issues for a flow battery. However, the degradation mechanism of ion exchange membranes has been rarely investigated especially for anion exchange membranes. Here, the degradation mechanism of polysulfone based anion exchange membranes, carrying pyridine ion exchange groups, under vanadium flow battery (VFB) medium was investigated in detail. We find that sp(2) hybrid orbital interactions between pyridinic-nitrogen in 4,4'-bipyridine and benzylic carbon disrupt the charge state balance of pristine chloromethylated polysulfone. This difference in electronegativity inversely induces an electrophilic carbon center in the benzene ring, which can be attacked by the lone pair electron on the vanadium(V) oxygen species, further leading to the degradation of polymer backbone, while leaving the 4,4'-bipyridine ion exchange groups stable. This work represents a step toward design and construction of alternative type of chemically stable hydrocarbon ion exchange membranes for VFB.
烃类离子交换膜的稳定性是液流电池的关键问题之一。然而，离子交换膜的降解机制很少被研究，尤其是阴离子交换膜。在此，详细研究了带有吡啶离子交换基团的聚砜基阴离子交换膜在钒液流电池（VFB）介质中的降解机制。我们发现，4,4'-联吡啶中的吡啶氮与苄基碳之间的sp(2)杂化轨道相互作用破坏了原始氯甲基化聚砜的电荷状态平衡。这种电负性差异反过来在苯环中诱导出一个亲电碳中心，它会被钒（V）氧物种上的孤对电子攻击，进一步导致聚合物主链的降解，而4,4'-联吡啶离子交换基团保持稳定。这项工作朝着设计和构建用于VFB的替代类型化学稳定烃类离子交换膜迈出了一步。
