Confined lamellar channels structured by multilayer graphene for high-efficiency desalination

As a versatile two-dimensional (2D) material, graphene has attracted an increasing amount of attention from different fields, e.g., Geim et al. (Science 2019, 363: 145-148) experimentally reported artificial graphene capillaries with a 2D slit of a few angstroms in height, where water fully moves through these capillaries and all salt ions are excluded. To understand the phenomenon observed experimentally, here we systematically investigate hydrodynamic properties of the lamellar graphene channels with different interlayer height, such as self-diffusion, viscosity and permeability of waters. Molecular dynamics simulations show that water viscosity decreases with the increasing of channel height, while the diffusion coefficient and flux of water enhance. For the channel with a height of 0.78 nm, the water permeability is far larger than the values of commercial reverse osmosis membranes, simultaneously exhibiting a salt rejection of > 95%. Besides, the simulated results show that the flexible channels initially filled with water will not collapse when the channels are formed by more than two layers of graphene sheets on each side. This work highlights the stability mechanism of the graphene channel, which will show its importance for future development of graphene membranes.