Microscopic dynamics of charge separation at the aqueous electrochemical interface
Microscopic dynamics of charge separation at the aqueous electrochemical interface
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DOI：
10.1073/pnas.1700093114
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发表时间：
2017-12-19
影响因子：
11.1
通讯作者：
Willard, Adam P.
中科院分区：
文献类型：
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作者：
Kattirtzi, John A.;Limmer, David T.;Willard, Adam P.
本文采用分子模拟和重要抽样方法研究了液态水-金属界面离子电荷分离的热力学和动力学。我们已经考虑了这个过程中使用的两个不同类别的离子的典型例子：一个简单的碱金属卤化物对，Na+I-，或经典的离子，和水的自电离，H3 O + OH-，或水离子的产品。我们发现，对于这两种离子类，电荷分离的微观机制，包括水的集体作用的过程中，是保守的散装液体和电极界面之间。然而，该过程的热力学和动力学细节在这两种环境之间以取决于离子类型的方式不同。在经典离子对的情况下，电荷分离的更高自由能势垒和在界面处越过该势垒的更小通量导致解离速率相对于本体慢40倍。对于水离子，一个稍高的自由能障碍是由一个较高的通量从较长寿命的氢键模式在界面上的障碍，导致在一个速率的协会是类似的，在和远离界面抵消。我们发现，电荷分离的速率和稳定性的这些差异是由于水的溶剂化和重组的金属界面附近的改变的能力。
We have used molecular simulation and methods of importance sampling to study the thermodynamics and kinetics of ionic charge separation at a liquid water-metal interface. We have considered this process using canonical examples of two different classes of ions: a simple alkali-halide pair, Na+I-, or classical ions, and the products of water autoionization, H3O+ OH-, or water ions. We find that for both ion classes, the microscopic mechanism of charge separation, including water's collective role in the process, is conserved between the bulk liquid and the electrode interface. However, the thermodynamic and kinetic details of the process differ between these two environments in a way that depends on ion type. In the case of the classical ion pairs, a higher free-energy barrier to charge separation and a smaller flux over that barrier at the interface result in a rate of dissociation that is 40 times slower relative to the bulk. For water ions, a slightly higher free-energy barrier is offset by a higher flux over the barrier from longer lived hydrogen-bonding patterns at the interface, resulting in a rate of association that is similar both at and away from the interface. We find that these differences in rates and stabilities of charge separation are due to the altered ability of water to solvate and reorganize in the vicinity of the metal interface.