Molecular dynamics simulations on the water flux in different two-dimension materials

The flow behaviour of water molecules in a slit compose of a two-dimensional material slit offers very important information that can be used for the design of high-flux seawater-desalination membranes. In this paper, the flux of water in three kinds of slit materials (graphene, hBN, and MoS2) with different slit widths (1.5, 2, and 3 nm) at room temperature and pressure is studied by nonequilibrium molecular dynamics simulation. We found that the flux of water in the hydrophobic graphene slit is three to four orders of magnitude larger than that in the slits built of hydrophilic hBN and MoS2 with the same slit width. The slit width also has a certain effect on the water flux. For hydrophobic materials, the water flux increases with increase in the slit width. For hydrophilic materials, the water flux increases first and then decreases with increases in the slit width, and the maximum value of flux is obtained when the slit width is about 2 nm. An analysis of the presence of hydrogen bonds showed that the hydrophilicity/hydrophobicity and slit width of materials affect the hydrogen bonding network of water, thus affecting the flux of water in two-dimensional materials.