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.

Recent advances in nanoporous graphene membrane for gas separation and water purification

“…Huang et al [85] demonstrated that the permeance (2.4 9 10 5 GPU for H 2 ) and selectivity (10 24 at room temperature) were significantly improved for the separation of H 2 /CH 4 by adopting an inter-layer-connected porous graphene bilayer. In a recent work by Wen et al [86], an inhibition effect of non-permeating components on the permeation of permeating component was identified ( Fig. 2e).…”

Mechanical and electromechanical properties of graphene and their potential application in MEMS

“…For example, tiny but precise holes can be used for desalinating sea water [197] and potentially for separating different gases [198,199]. The desired porosity can be achieved in a number of ways, such as ion bombardment [200,201], electron beam irradiation [202], chemical etching and surface-assisted aryl-aryl coupling of cyclohexa-m-phenylene [203,204]. A free-standing nanoporous monolayer graphene membrane is a single atom thick (∼3 Å) , which is close to the stacking distance (∼3.4 Å) of a DNA base pair [205].…”

Molecular sieving through a graphene nanopore: non-equilibrium molecular dynamics simulation

“…Therefore, the molecular adsorption on both sides of the graphene surface is in a quasiequilibrium state. It is noted that, in the simulations, the separations of CO 2 and H 2 S molecules from CH 4 molecules are conducted separately; in the event that the CO 2 and H 2 S molecules are mixed together and simultaneously separated from CH 4 molecules, the adsorption of one component would be decreased due to the competitive mechanism, which can induce a reduction in the permeation rate of this component, as illustrated by Wen et al [34].…”

“…Until now, most of the relevant studies have been conducted based on theoretical calculations due to their practicability and low economic cost, especially in regard to molecular dynamics (MD) and density functional theory methods. The effects of surface adsorption [31][32][33], nonpermeating component [34], chemical modifications [35,36] and others on molecular permeation were elucidated. Lei et al [37] tested the sieving effect of a pristine graphene nanopore for the separation of H 2 S/CH 4 and revealed the effects of atomic charges by adding charges on the pore-rim carbon atoms.…”