Inhibition effect of a non-permeating component on gas permeability of nanoporous graphene membranes

Abstract

We identify the inhibition effect of a non-permeating gas component on gases permeating through the nanoporous graphene membranes and reveal its mechanisms from molecular dynamics insights. The membrane separation process involves the gas mixtures of CH₄/H₂ and CH₄/N₂ with different partial pressures of the non-permeating gas component (CH₄). The results show that the permeance of the H₂ and N₂ molecules decreases sharply in the presence of the CH₄ molecules. The permeance of the N₂ molecules can be reduced to as much as 64.5%. The adsorption of the CH₄ molecules on the graphene surface weakens the surface adsorption of the H₂ and N₂ molecules due to a competitive mechanism, accordingly reducing the permeability of the H₂ and N₂ molecules. For the N₂ molecules with stronger adsorption ability, the reduction of the permeance is greater. On the other hand, the CH₄ molecules near the nanopore have a blocking effect, which further inhibits the permeation of the H₂ and N₂ molecules. In addition, we predict the selectivity of the nanopore by using density functional theory calculations. This work can provide valuable guidance for the application of nanoporous graphene membranes in the separation of the gas mixtures consisting of permeating and non-permeating components with different adsorption abilities.