CH4 and CO2 Transport Properties through Nanoporous Graphene and Graphene Oxide Membranes: A Molecular Dynamics Simulation Study

Molecular dynamics simulations were performed to investigate the gas transport properties of a CH₄/CO₂ gaseous mixture in single- and double-layered nanoporous graphene (NPG) and graphene oxide (NPGO) membranes. An increase in the CH₄ concentration was found to improve the through-the-pore diffusion coefficients of both CO₂ and CH₄ for both single- and double-layered membranes. The CO₂ permeance is smaller than that of CH₄ for all membrane configurations, in agreement with the diffusion coefficients of both gases. Therefore, a CH₄/CO₂ separation is realized in the NPG and NPGO membranes due to a faster permeance of CH₄ than CO₂. The highest and lowest permeances for CO₂ are for the single-layered NPG and the double-layered NPGO membrane, respectively. The perm-selectivities of both NPG and NPGO membranes were determined based on the number of gas molecules passing through the membranes and the gas permeances. The single- and double-layered NPG and NPGO membranes demonstrate a satisfactory performance for the CH₄/CO₂ separation. Furthermore, the adsorption- and perm-selectivity of the double-layered NPGO membranes show improvement when compared to the single-layered NPGO membranes.