The Water Flow through Graphene Slit Pores: Insights from Non-Equilibrium Molecular Dynamics Simulations

Water flowing through graphene membranes draws much attention of scientists since the excellent performance of water flux. The efforts at preparing graphene membranes have been made for years, but there are few cases of stable graphene membranes that could be applied into industrial applications. Some researchers tried to figure out the mechanism of high water flux in graphene pores, so as to design some polymer or inorganic membranes with excellent mass transport properties. In this work, we investigate the phenomenon of water flow through graphene slit pores by non-equilibrium molecular dynamics (NEMD) simulations. As was expected, the average velocities of water molecules get boosted with the additional force being enhanced. Besides, we tuned the slit width of graphene pores to figure out the effect of geometric size on the water flow. The slit pore size was chosen from 0.65 nm to 1.40 nm, so the water structure inside the graphene pore is switching from single layer to double layers. Since the microstructure of water confined in graphene is different, the mechanism of water transport is various. Unexpectedly, the water flux is not promoted with the slit width monotonically. The flux of water in 0.85 nm graphene slit pores exhibits minimum, probably due to the single – double layer switching.