Enforced Freedom: Electric‐Field‐Induced Declustering of Ionic‐Liquid Ions in the Electrical Double Layer
Enforced Freedom: Electric‐Field‐Induced Declustering of Ionic‐Liquid Ions in the Electrical Double Layer
复制标题
强制自由：电场诱导双电层中离子的分裂
DOI：
10.1002/eem2.12107
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发表时间：
2020
影响因子：
15
通讯作者：
Alexei A. Kornyshev
中科院分区：
文献类型：
--
作者：
Yufan Zhang;Ting Ye;Ming Chen;Zachary A.H. Goodwin;Guang Feng;Jun Huang;Alexei A. Kornyshev
无溶剂离子液体中的离子结合成离子对和离子簇。离子保持在束缚态的倾向与在电场中解束缚时能量的降低之间的竞争决定了双电层中自由离子的部分。我们提出了最简单的平均场理论来研究这种效应。离子对在电场中“裂解”成自由离子伴随着离子液体介电响应的变化。从理论的预测进行了验证，并进一步探讨了分子动力学模拟。该理论的一个特别发现是，尽管自由电荷载流子的浓度较低，但微分电容与电势曲线显示出钟形，因为介电响应降低了钟形到骆驼形转变的阈值浓度。该理论没有考虑双电层中的过屏蔽和振荡电荷分布。但是，尽管模型很简单，它的研究结果表明了一个明确的物理效应：在强电场中，优先成为带电的偶极子而不是偶极子（或高阶多极子）。
Ions in the bulk of solvent‐free ionic liquids bind into ion pairs and clusters. The competition between the propensity of ions to stay in a bound state, and the reduction of the energy when unbinding in electric field, determines the portion of free ions in the electrical double layer. We present the simplest possible mean‐field theory to study this effect. “Cracking” of ion pairs into free ions in electric field is accompanied by the change of the dielectric response of the ionic liquid. The predictions from the theory are verified and further explored by molecular dynamics simulations. A particular finding of the theory is that the differential capacitance vs potential curve displays a bell shape, despite the low concentration of free charge carriers, because the dielectric response reduces the threshold concentration for the bell‐ to camel‐shape transition. The presented theory does not take into account overscreening and oscillating charge distributions in the electrical double layer. But in spite of the simplicity of the model, its findings demonstrate a clear physical effect: a preference to be a charged monopole rather than a dipole (or higher order multipole) in strong electric field.