Flow of quasi-two dimensional water in graphene channels
Flow of quasi-two dimensional water in graphene channels
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DOI：
10.1063/1.5017491
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发表时间：
2018-02-14
影响因子：
4.4
通讯作者：
Qiao, Rui
中科院分区：
文献类型：
--
作者：
Fang, Chao;Wu, Xihui;Qiao, Rui
当限制在狭缝通道中的液体接近单层时，它们变成二维（2D）流体。使用分子动力学模拟，我们研究了准二维水限制在狭缝通道具有原始石墨烯壁和石墨烯壁与羟基基团的流动。我们专注于在何种程度上的准二维水的流动可以用经典流体力学和什么是有效的水和通道的传输特性。首先，限制在原始石墨烯之间的准二维水的平面内剪切可以使用经典流体动力学方程来描述，并且水的粘度比这里研究的通道中的本体水的粘度高50%。其次，准二维水围绕一个单一的羟基基团的流动是扰动在几十个集群半径的位置从它的中心，如预期的低雷诺数流动。即使水没有固定在羟基的边缘，羟基也会极大地屏蔽流动，单个孤立的羟基会产生类似于90 nm（2）原始石墨烯壁的阻力。最后，准2D水通过具有随机分布的羟基基团的石墨烯通道的流动类似于通过多孔介质的流体流动。通道的有效摩擦系数在0.5nm（-2）以下随羟基的面密度线性增加，但在更高的密度下非线性增加。通道的有效摩擦因子可以拟合到至少高达2.0 nm（-2）的羟基面积密度的修改的卡曼方程。这些发现有助于了解基于2D材料的纳米通道中的液体传输，用于包括脱盐在内的应用。出版社：AIP Publishing
When liquids confined in slit channels approach a monolayer, they become two-dimensional (2D) fluids. Using molecular dynamics simulations, we study the flow of quasi-2D water confined in slit channels featuring pristine graphene walls and graphene walls with hydroxyl groups. We focus on to what extent the flow of quasi-2D water can be described using classical hydrodynamics and what are the effective transport properties of the water and the channel. First, the in-plane shearing of quasi-2D water confined between pristine graphene can be described using the classical hydrodynamic equation, and the viscosity of the water is similar to 50% higher than that of the bulk water in the channel studied here. Second, the flow of quasi-2D water around a single hydroxyl group is perturbed at a position of tens of cluster radius from its center, as expected for low Reynolds number flows. Even though water is not pinned at the edge of the hydroxyl group, the hydroxyl group screens the flow greatly, with a single, isolated hydroxyl group rendering drag similar to similar to 90 nm(2) pristine graphene walls. Finally, the flowof quasi-2D water through graphene channels featuring randomly distributed hydroxyl groups resembles the fluid flow through porous media. The effective friction factor of the channel increases linearly with the hydroxyl groups' area density up to 0.5 nm(-2) but increases nonlinearly at higher densities. The effective friction factor of the channel can be fitted to a modified Carman equation at least up to a hydroxyl area density of 2.0 nm(-2). These findings help understand the liquid transport in 2D material-based nanochannels for applications including desalination. Published by AIP Publishing.