Theoretical description of molecular permeation <i>via</i> surface diffusion through graphene nanopores

Sun, Chengzhen; Luo, Kailin; Zhou, Runfeng; Bai, Bofeng

doi:10.1039/d0cp05629d

Cited by 9 publications

(11 citation statements)

References 41 publications

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“…[61,63,64,66] Furthermore, these MD simulation methods are essential in order to confirm and refine the analytical descriptions discussed in Section 2.1. [59,106] A useful way to predict the gas permeance per pore through a high-energy-barrier NATM pore using MD simulations is to artificially add a bias potential to force the gas molecule through the pore. A widely utilized technique is umbrella sampling, where a series of local harmonic bias potential wells are used to offset the high energy barrier.…”

Section: Simulationsmentioning

confidence: 99%

“…In this regard, atomic‐scale simulations have been carried out to estimate the gas permeances more precisely. Figure summarizes the simulation results of gas permeation through NATM pores using molecular dynamics (MD) simulations, [ 59,61,63,64,66,67,73–75,86–107 ] ab initio calculations, [ 29,70,83,108–121 ] or a combination of both, [ 72,82,122–137 ] as well as experimental results of gas permeation through individual graphene nanopores. [ 60,138 ] The gases considered in Figure 4 include H 2 , He, H 2 O, CO 2 , N 2 , O 2 , CH 4 , H 2 S, Ar, SF 6 , ethane, and ethene.…”

Section: Theoretical and Simulation Advancesmentioning

confidence: 99%

“…a) Compilation of simulation, analytical modeling, and experimental data of gas permeance per pore (normalized by the square root of the gas molecular weight) as a function of the pore diameter D p (normalized by the gas kinetic diameter D m ). The simulation methods used include MD, [ 59,61,63,64,66,67,73–75,86–107 ] ab initio calculations, [ 29,70,83,108–121 ] and a combination of both. [ 72,82,122–137 ] The experimental results are taken from ref.…”

Section: Theoretical and Simulation Advancesmentioning

confidence: 99%

“…[ 61,63,64,66 ] Furthermore, these MD simulation methods are essential in order to confirm and refine the analytical descriptions discussed in Section 2.1. [ 59,106 ]…”

Section: Theoretical and Simulation Advancesmentioning

confidence: 99%

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Gas Separations using Nanoporous Atomically Thin Membranes: Recent Theoretical, Simulation, and Experimental Advances

Yuan

et al. 2022

Advanced Materials

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The separation of gaseous mixtures is essential in the chemical industry, including hydrogen separation in ammonia or petrochemical plants, nitrogen separation from air, CO 2 separation in natural gas processing, [7] olefin/ paraffin separation, [1] and H 2 S separation from sour gas. [8] Similar to separation processes in general, thermal-based gasseparation methods, such as cryogenic distillation, amine adsorption, and vapor condensation, consume a high amount of energy, which can be significantly reduced using gas-separation membrane units. [5,8] A membrane that can separate gases allows certain components in a mixture to permeate at higher rates than others. The economic competitiveness of a gas-separation membrane highly depends on its gas permeance K and its selectivity S. The permeance K i of gas species i (in SI units of mol m −2 s −1 Pa −1 ) is defined as K i = F i /Δp i , where F i (in SI units of mol m −2 s −1 ) is the flux of gas i through the membrane, and Δp i is the partial pressure difference (the driving force) of gas i between the feed side and the permeate side. For relatively thick conventional membranes, whose crossmembrane transport resistance is dominated by the bulk interior, the permeance K i is inversely proportional to the membrane thickness d. Correspondingly, the permeability P i of gas i (in SI units of mol m −1 s −1 Pa −1 ) is defined aswhich is an intrinsic property of a material. The selectivity S ij between gases i and j is defined as S ij = K i /K j = P i /P j .Polymers have been the most widely used materials for gasseparation membranes for decades because of their relatively low cost and low manufacturing difficulty. [8,9] However, membrane separations using state-of-the-art polymeric membranes cannot outcompete the thermal-based separation methods economically. [7] One of the limitations of the polymeric membranes is the trade-off between permeability and selectivity, originally investigated by Robeson. [10,11] The best combination of permeability and selectivity for a binary gas pair is referred to as the polymer upper bound. This trade-off originates from the interplay between the free volume spacing in the polymer matrices and the size of the gas molecules. [12] Smaller polymeric spacing increases the selectivity but sacrifices the permeability due to the lower gas Porous graphene and other atomically thin 2D materials are regarded as highly promising membrane materials for high-performance gas separations due to their atomic thickness, large-scale synthesizability, excellent mechanical strength, and chemical stability. When these atomically thin materials contain a high areal density of gas-sieving nanoscale pores, they can exhibit both high gas permeances and high selectivities, which is beneficial for reducing the cost of gas-separation processes. Here, recent modeling and experimental advances in nanoporous atomically thin membranes for gas separations is discussed. The major challenges involved, including controlling pore size distributions, scaling up the membrane ar...

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Section: Simulationsmentioning

confidence: 99%

Section: Theoretical and Simulation Advancesmentioning

confidence: 99%

Section: Theoretical and Simulation Advancesmentioning

confidence: 99%

“…[ 61,63,64,66 ] Furthermore, these MD simulation methods are essential in order to confirm and refine the analytical descriptions discussed in Section 2.1. [ 59,106 ]…”

Section: Theoretical and Simulation Advancesmentioning

confidence: 99%

See 2 more Smart Citations

Gas Separations using Nanoporous Atomically Thin Membranes: Recent Theoretical, Simulation, and Experimental Advances

Yuan

et al. 2022

Advanced Materials

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“…Currently, the industrial-scale NPG membranes have been successfully synthesized with a high molecular permeance as the theoretically expected (Boutilier et al, 2017;Wang et al, 2017;Zhao et al, 2019). Meanwhile, the molecular permeation mechanisms through NPG membranes were also well revealed (Drahushuk and Strano, 2012;Sun et al, 2014;Yuan et al, 2017;Sun et al, 2019a;Sun et al, 2021a;Sun et al, 2021b). In short, the NPG membranes for molecular separation has become a reality, especially for the application of gas separation.…”

Section: Introductionmentioning

confidence: 93%

Quasi-Unidirectional Transport Bilayer Two-Dimensional Nanopores for Highly-Efficient Molecular Sieving

et al. 2021

Self Cite

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Two-dimensional nanopores are very promising for high-permeance molecular sieving, but the molecular backflow from permeate-side to feed-side is not beneficial for improving molecular permeance. We study the quasi-unidirectional molecular transport through a graphene-hexagonal boron nitride bilayer nanopore, aiming to realize a high-permeance molecular sieving. Molecular dynamics simulations of CO2/CH4 separations show that the bilayer pore presents 3.7 times higher selectivity comparing to the single-layer graphene nanopore with the same size. The quasi-unidirectional molecular transport is attributed to the distinctive adsorption abilities of gas molecules on the two sides of bilayer nanopores and the inhibited molecular backflow from permeate-side to feed-side. This work provides a promising way to realize the ultra-permeable porous membranes with molecular permeance even higher than the single-layer atomic-thickness membranes.

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Size and Shape Exclusion in 2D Silicon Dioxide Membranes

Dementyev

Khayya

Zanders

et al. 2022

Small

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2D membranes such as artificially perforated graphene are deemed to bring great advantages for molecular separation. However, there is a lack of structure‐property correlations in graphene membranes as neither the atomic configurations nor the number of introduced sub‐nanometer defects are known precisely. Recently, bilayer silica has emerged as an inherent 2D membrane with an unprecedentedly high areal density of well‐defined pores. Mass transfer experiments with free‐standing SiO2 bilayers demonstrated a strong preference for condensable fluids over inert species, and the measured membrane selectivity revealed a key role of intermolecular forces in ångstrom‐scale openings. In this study, vapor permeation measurements are combined with quantitative adsorption experiments and density functional theory (DFT) calculations to get insights into the mechanism of surface‐mediated transport in vitreous 2D silicon dioxide. The membranes are shown to exhibit molecular sieving performance when exposed to vaporous methanol, ethanol, isopropanol, and tert‐butanol. The results are normalized to the coverage of physisorbed molecules and agree well with the calculated energy barriers.

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Theoretical description of molecular permeation via surface diffusion through graphene nanopores

Abstract: We establish a theoretical model to describe the surface molecular permeation through two-dimensional graphene nanopores based on the surface diffusion equation and Fick’s law. The model is established by considering...

Cited by 9 publications

References 41 publications

Gas Separations using Nanoporous Atomically Thin Membranes: Recent Theoretical, Simulation, and Experimental Advances

Gas Separations using Nanoporous Atomically Thin Membranes: Recent Theoretical, Simulation, and Experimental Advances

Quasi-Unidirectional Transport Bilayer Two-Dimensional Nanopores for Highly-Efficient Molecular Sieving

Size and Shape Exclusion in 2D Silicon Dioxide Membranes

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