Molecular and continuum hydrodynamics in graphene nanopores

Abstract

An ultrathin graphene membrane is a promising candidate for various applications such as gas separation, water purification, biosensors, etc. In this study, we investigate water transport mechanisms and hydrodynamic properties such as water flux, pressure variation, velocity, viscosity, slip length, etc. Due to the unique water structure, confined in the radial direction and layered in the axial direction of the pore, water viscosity and slip length increase with a decrease in the pore radius, in contrast to water confined in a carbon nanotube. As the diameter of the pore increases, the water transport mechanism transitions from collective diffusion to frictional flow described by the modified Hagen–Poiseuille equation. Graphene membrane is shown to be ultra-efficient by comparing the permeation coefficient of graphene membrane to that of a carbon nanotube and an ultrathin silicon membrane. We envision that the study presented here will help to understand and design various membrane separation processes using graphene membrane.