Water in Ionic Liquids at Electrified Interfaces: The Anatomy of Electrosorption
Water in Ionic Liquids at Electrified Interfaces: The Anatomy of Electrosorption
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带电界面离子液体中的水：电吸附的剖析
DOI：
10.1021/nn505017c
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发表时间：
2014-11-01
期刊：
影响因子：
17.1
通讯作者：
Kornyshev, Alexei A.
中科院分区：
文献类型：
--
作者：
Feng, Guang;Jiang, Xikai;Kornyshev, Alexei A.
从室温离子液体中完全除去水几乎是不可能的。对于离子液体的电化学应用，当本体液体不完全干燥时，水如何分布在双电层中可以潜在地决定离子液体的关键优势，例如宽的电化学窗口，是否可以在实际系统中利用。在本文中，我们研究了水的吸附在电极表面接触潮湿，咪唑基离子液体使用分子动力学模拟。结果表明，水分子倾向于聚集在亚纳米距离的带电电极。在低量的水在散装，离子的分布和静电势的双电层中的水的存在的影响很弱，但水分子的空间分布强烈依赖于两者。水分子在双层中的优先位置是由几个因素的平衡决定的：遵循电场最大绝对值位置的趋势，与其离子环境的关联，以及在更多自由空间可用的位置上沉降的倾向。这些因素之间的平衡随着电极的充电而改变，但水的吸附通常随着电压而增加。水电吸附的离子特异性表现为水在正电极附近（其中阴离子是抗衡离子）比在负电极附近（其中阳离子是抗衡离子）更强地存在。这些预言有待实验验证。
Complete removal of water from room-temperature ionic liquids is nearly impossible. For the electrochemical applications of ionic liquids, how water is distributed in the electrical double layers when the bulk liquids are not perfectly dry can potentially determine whether key advantages of ionic liquids, such as a wide electrochemical window, can be harnessed in practical systems. In this paper, we study the adsorption of water on electrode surfaces in contact with humid, imidazolium-based ionic liquids using molecular dynamics simulations. The results revealed that water molecules tend to accumulate within sub-nanometer distance from charged electrodes. At low amount of water in the bulk, the distributions of ions and of electrostatic potential in the double layer are affected weakly by the presence of water, but the spatial distribution of water molecules is strongly dependent on both. The preferential positions of water molecules in double layers are determined by the balance of several factors: the tendency to follow the positions of the maximal absolute value of the electrical field, the association with their ionic surroundings, and the propensity to settle at positions where more free space is available. The balance between these factors changes with charging the electrode, but the adsorption of water generally increases with voltage. The ion specificity of water electrosorption is manifested in the stronger presence of water near positive electrodes (where anions are the counterions) than near negative electrodes (where cations are counterions). These predictions await experimental verification.