Grotthuss versus Vehicular Transport of Hydroxide in Anion-Exchange Membranes: Insight from Combined Reactive and Nonreactive Molecular Simulations
Grotthuss versus Vehicular Transport of Hydroxide in Anion-Exchange Membranes: Insight from Combined Reactive and Nonreactive Molecular Simulations
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DOI：
10.1021/acs.jpclett.8b00004
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发表时间：
2018-02-15
影响因子：
5.7
通讯作者：
Bedrov, Dmitry
中科院分区：
文献类型：
--
作者：
Dong, Dengpan;Zhang, Weiwei;Bedrov, Dmitry
结合反应性和非反应性极化分子动力学模拟被用来探测氢氧化物在水合阴离子交换膜（AEM）组成的聚（对苯醚）功能化与季铵阳离子基团的传输机制。两种模型之间的膜形态的直接映射，使我们能够调查车辆和Grotthuss机制在氢氧化物运动的贡献，并将这些机制与局部结构的细节。在具有非块状聚合物结构的AEM中，阴离子运输通过狭窄（亚纳米尺寸）的膨胀水通道发生，模拟表明Grotthuss机制的重要性。在非反应性模拟中，为了通过水通道中的瓶颈扩散，氢氧根阴离子必须失去其水合结构的一部分，因此为此类事件创建了一个大的动力学屏障。然而，当涉及Grotthuss机制时，通过这些瓶颈的氢氧化物运输可以容易地发生，而不会损失阴离子水合结构，并且具有低得多的屏障。
Combined reactive and nonreactive polarizable molecular dynamics simulations were used to probe the transport mechanisms of hydroxide in hydrated anion-exchange membranes (AEMs) composed of poly(p-phenylene oxide) functionalized with the quaternary ammonium cationic groups. The direct mapping of membrane morphologies between two models allowed us to investigate the contributions of vehicular and Grotthuss mechanisms in hydroxide motion and correlate these mechanisms with the details of local structure. In AEMs with nonblocky polymer structure, where anion transport occurs through narrow (subnanometer size) percolating water channels, simulations indicate the importance of the Grotthuss mechanism. In nonreactive simulations, in order to diffuse through bottlenecks in the water channels, the hydroxide anion has to lose part of its hydration structure, therefore creating a large kinetic barrier for such events. However, when the Grotthuss mechanism is involved, the hydroxide transport through these bottlenecks can easily occur without loss of anion hydration structure and with a much lower barrier.