Mechanisms of Gas Permeation through Single Layer Graphene Membranes

Abstract

Graphene has enormous potential as a unique molecular barrier material with atomic layer thickness, enabling new types of membranes for separation and manipulation. However, the conventional analysis of diffusive transport through a membrane fails in the case of single layer graphene (SLG) and other 2D atomically thin membranes. In this work, analytical expressions are derived for gas permeation through such atomically thin membranes in various limits of gas diffusion, surface adsorption, or pore translocation as the rate-limiting step. Gas permeation can proceed via direct gas-phase interaction with the pore, or interaction via the adsorbed phase on the membrane exterior surface. A series of van der Waals force fields allows for the estimation of the energy barriers present for various types of graphene nanopores. These analytical models will assist in the understanding of molecular dynamics and experimental studies of such membranes.

Low Dimensional Carbon Materials for Applications in Mass and Energy Transport

“…12 This model uses multiple steps describing the adsorption and desorption, entering and leaving the pore area, and passing through the pore. An example of this process with the molecular positions and corresponding energy is shown in Figure 4A−C.…”

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

“…41 Porous two-layer graphene membranes with various pore sizes, 42 prepared by focused ion beam etching and photo lithography, exhibit 43 good separation ratios for CO 2 and H 2 for pore diameters below 44 10 nm. 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].…”

“…(100) [40]. 314 When discussing the application of graphene as a gas barrier, the in- about a similar size as argon [45,46]. While the graphene sheet is still 326 bonded to the nickel surface, carbon atoms at vacancies are proposed 327 to bind particularly strong to the substrate, and thus prevent argon 328 from desorbing through such vacancies [24].…”

Recent developments in membranes for efficient hydrogen purification

“…However, gas transport mechanism through porous graphene-based membranes remains elusive. Several researchers have attempted to explore gas transport mechanism using different simulation methods [92,[99][100][101]. The gas transport mechanisms of conventional gas separation membranes may be not suitable for porous graphene membranes with single-atom thickness, while the widely accepted viewpoint is that the permeation of gas molecules through porous graphene membranes is closely related to both transport rate to the surface and molecular adsorption on the graphene sheet surface, as well as the size and functionalization of pores.…”