Tunable Hydrogen Separation in Porous Graphene Membrane: First-Principle and Molecular Dynamic Simulation

Abstract

First-principle density functional theory (DFT) calculation and molecular dynamic (MD) simulation are employed to investigate the hydrogen purification performance of two-dimensional porous graphene material (PG-ESX). First, the pore size of PG-ES1 (3.2775 Å) is expected to show high selectivity of H2 by DFT calculation. Then MD simulations demonstrate the hydrogen purification process of the PG-ESX membrane. The results indicate that the selectivity of H2 over several other gas molecules that often accompany H2 in industrial steam methane reforming or dehydrogenation of alkanes (such as N2, CO, and CH4) is sensitive to the pore size of the membrane. PG-ES and PG-ES1 membranes both exhibit high selectivity for H2 over other gases, but the permeability of the PG-ES membrane is much lower than the PG-ES1 membrane because of the smaller pore size. The PG-ES2 membrane with bigger pores demonstrates low selectivity for H2 over other gases. Energy barrier and electron density have been used to explain the difference of selectivity and permeability of PG-ESX membranes by DFT calculations. The energy barrier for gas molecules passing through the membrane generally increase with the decreasing of pore sizes or increasing of molecule kinetic diameter, due to the different electron overlap between gas and a membrane. The PG-ES1 membrane is far superior to other carbon membranes and has great potential applications in hydrogen purification, energy clean combustion, and making new concept membrane for gas separation.

Keeping argon under a graphene lid—Argon intercalation between graphene and nickel(111)

“…Furthermore, strong improvements in the permeance of water, 45 water vapor and oxygen were achieved, as compared to current state- 46 of-the-art membranes [18]. However, the preparation of well-defined 47 pores for very high separation ratios is still challenging, as it requires 48 manipulation of graphene on an atomic scale and sometimes special 49 edge termination [12,19]. 50 Several groups investigated the properties of graphene as mem-51 brane for gas containment, and for corrosion inhibition with various 52 techniques; one example is a micro chamber etched into a SiO 2 53 substrate sealed with transferred graphene that was investigated with 54 atomic force microscopy (AFM) [9].…”

Nanoporous graphene oxide membrane and its application in molecular sieving

“…All molecular dynamic simulations were performed in an NVT enable to gases [7]. However, several studies have suggested that graphene has the potential to induce highly selective transport by generation of pore defects [8][9][10][11][12][13][14], in which atoms can be removed from the graphene lattice to create pores of specific size and geometry.…”

Recent developments in membranes for efficient hydrogen purification

“…Over the past five years, many computational studies have suggested that porous graphene-based membranes with desirable pore geometry could achieve an excellent permeance and selectivity [75,[91][92][93] [84]. In this study, the micrometer-scale membranes with sub-nanometer-sized pores were created via ultraviolet oxidative etching method, and the gas leak experiments indicated that the gas molecules with the kinetic diameter smaller than 3.4 Å were much more permeable than those with the kinetic diameter larger than 3.4 Å. Consequently, the H 2 /CO 2 ideal selectivity was about 1.7, which was likely due to the larger pore size than CO 2 and H 2 molecules.…”