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

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.