Molecular permeation in nanoporous graphene gas separation membranes

A molecular dynamics simulation was performed to probe the mechanism of molecular permeation through nanoporous graphene gas separation membranes. The investigation involves 4 different gas molecules (He, H₂, N₂ and CH₄) permeating 9 graphene nanopores with different sizes. The results show that the permeation flux depends not only on the kinetic parameters of molecules, i. e. molecular mass and kinetic diameter, but also on the adsorption of molecules on the surface of graphene membrane. Apart from the permeation free of interactions with the graphene surface, the adsorption layer composed of molecules with high densities on the graphene surface provides an additional way for molecular permeation, increasing the permeation flux as the molecular adsorption increases. In addition, the permeation flux of H₂ molecules increases linearly with the pressure for different graphene nanopores.