Reverse osmosis membranes hold great promise for dealing with global water scarcity. However, the trade-off between ion selectivity and water permeability is a serious obstacle to desalination. Herein, we introduce an effective strategy to enhance the desalination performance of the membrane. A series of molecular dynamics simulations manifest that an additional lateral electric field significantly promotes ion rejection in carbon nanotubes (CNTs) under the drive of longitudinal pressure. Specifically, with the increase in the electric field, the ion flux shows a deep linear decay, while the water flux decreases only slightly, resulting in a linear increase in ion rejection. The energy barriers of ions around the CNT inlet are obtained by calculating the potentials of mean force to explain enhanced ion rejection. The lateral electric field uniformly raises the energy barriers of ions by pushing them away from the CNT inlet, corresponding to the enhanced ion velocity in the field direction. Furthermore, with the increase in CNT diameter, there is a significant increase in the flux of both ions and water; however, the lateral electric field can also obviously enhance the ion rejection in wider CNTs. Consequently, the enhancement of ion rejection by lateral electric fields should be universal for different CNT diameters, which opens a new avenue for selective permeation and may have broad implications for desalination devices with large pore sizes.

中文翻译：

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横向电场增强碳纳米管中的离子排斥

反渗透膜在应对全球水资源短缺方面大有希望。然而，离子选择性和水渗透性之间的权衡是海水淡化的一个严重障碍。在这里，我们介绍了一种有效的策略来提高膜的脱盐性能。一系列分子动力学模拟表明，在纵向压力的驱动下，额外的横向电场显着促进了碳纳米管 (CNT) 中的离子排斥。具体来说，随着电场的增加，离子通量表现出深度的线性衰减，而水通量仅略有下降，导致离子排斥线性增加。通过计算平均力的势能来获得 CNT 入口周围离子的能垒，以解释增强的离子排斥。横向电场通过将离子推离 CNT 入口来均匀地提高离子的能垒，这与场方向上离子速度的增强相对应。此外，随着 CNT 直径的增加，离子和水的通量都显着增加；然而，横向电场也可以明显增强更宽碳纳米管中的离子排斥。因此，横向电场对离子排斥的增强对于不同的碳纳米管直径应该是普遍的，这为选择性渗透开辟了一条新途径，并且可能对大孔径的脱盐装置产生广泛的影响。离子和水的通量显着增加；然而，横向电场也可以明显增强更宽碳纳米管中的离子排斥。因此，横向电场对离子排斥的增强对于不同的碳纳米管直径应该是普遍的，这为选择性渗透开辟了一条新途径，并且可能对大孔径的脱盐装置产生广泛的影响。离子和水的通量显着增加；然而，横向电场也可以明显增强更宽碳纳米管中的离子排斥。因此，横向电场对离子排斥的增强对于不同的碳纳米管直径应该是普遍的，这为选择性渗透开辟了一条新途径，并且可能对大孔径的脱盐装置产生广泛的影响。