Guo Juncheng, Galliero Guillaume, Vermorel Romain
Université de Pau et des Pays de L'Adour, E2S UPPA, CNRS, TotalEnergies, LFCR, Pau, France.
J Chem Phys. 2023 Aug 28;159(8). doi: 10.1063/5.0161980.
In this paper, we study the permeation of polyatomic gas molecules through 2D graphene membranes. Using equilibrium molecular dynamics simulations, we investigate the permeation of pure gas compounds (CH4, CO2, O2, N2, and H2) through nanoporous graphene membranes with varying pore sizes and geometries. Our simulations consider the recrossing mechanism, often neglected in previous studies, which has a significant effect on permeation for intermediate pore size to molecular diameter ratios. We find that the permeation process can be decoupled into two steps: the crossing process of gas molecules through the pore plane and the escaping process from the pore region to a neighboring adsorption site, which prevents recrossing. To account for these mechanisms, we use a permeance model expressed as the product of the permeance for the crossing process and the probability of molecule escape. This phenomenological model is extended to account for small polyatomic gas molecules and to describe permeation regimes ranging from molecular sieving to effusion. The proposed model captures the temperature dependence and provides insights into the key parameters of the gas/membrane interaction controlling the permeance of the system. This work lays the foundation for predicting gas permeance and exploring membrane separation factors in 2D materials such as graphene.
在本文中，我们研究了多原子气体分子透过二维石墨烯膜的渗透情况。利用平衡分子动力学模拟，我们研究了纯气体化合物（CH4、CO2、O2、N2和H2）透过具有不同孔径和几何形状的纳米多孔石墨烯膜的渗透过程。我们的模拟考虑了再穿越机制，这在以往的研究中常常被忽略，而它对中等孔径与分子直径比的渗透过程有显著影响。我们发现，渗透过程可以分解为两个步骤：气体分子穿过孔平面的过程以及从孔区域逸出到相邻吸附位点的过程，后者可防止再穿越。为了解释这些机制，我们使用了一个渗透模型，该模型表示为穿越过程的渗透率与分子逸出概率的乘积。这个唯象模型被扩展以适用于小的多原子气体分子，并描述从分子筛分至泻流的渗透状态。所提出的模型捕捉了温度依赖性，并深入了解了控制系统渗透率的气体/膜相互作用的关键参数。这项工作为预测二维材料（如石墨烯）中的气体渗透率和探索膜分离因子奠定了基础。
