High directional water transport graphene oxide biphilic stack

It is a widely held view that the hydrophilicity of graphene oxide (GO) enhances the water transport properties. In this study, it is shown that a combination of graphene and GO can yield superior transport properties including high mass flow rate and directionality. First, different membrane characteristics such as the smallest pore diameter for water molecules sieving and mass flow rate are evaluated. Furthermore, a combination of graphene and GO, a biphilic stack of hydrophobic and hydrophilic layers, is used to evaluate the mass flow rates and results are compared with that of normal GO laminates. This structure acts as a water diode i.e. conducts water molecules in the desired direction and increases the mass flow rate several times. The effects of interatomic potential, oxidation level and charge, and the spacing between layers on mass flow rate and directionality are examined. It is found that an optimized structure conducts water in the desired direction and increases mass flow rate up to 10 times for small interlayer distance of 7 angstrom compared with normal GO laminates. The given structures can be used in a wide range of filtration applications, where selective water sieving with a high mass flow rate is desired.