Molecular dynamics simulation studies were employed to investigate the microscopic behaviors of CH₄ and CO₂ molecules in slit-nanopores (SNPs) with various surfaces and different compositions. Three kinds of SNPs were constructed by a pair-wise combination of graphene, silica, and the calcite surface. The grand canonical Monte Carlo and molecular dynamics simulation methods were used to investigate the adsorption and self-diffusion of the gases in the nanopores. It is found that in all three cases, the CH₄ molecules prefer to adsorb onto the graphene surface, whereas the CO₂ molecules prefer to adsorb onto the calcite surface. The adsorption intensity of gases adsorbed onto various surfaces, the adsorption distances, along with the details of adsorption orientations of CH₄ and CO₂ molecules on various surfaces are calculated. The surface characteristics, such as surface roughness and charge distribution, are analyzed to help understand the microscopic adsorption behaviors of the gases on the specific surface. It was found that competitive adsorptions of CO₂ over CH₄ broadly occurred, especially in the SNPs containing calcite, because of the strong adsorption interactions between the CO₂ molecules and the calcite surface. This work provides the microbehaviors of CH₄ and CO₂ in SNPs with various surfaces in different compositions to provide useful guidance for better understanding about the microstate of gases in complex nanoporous shale formation and to give out useful guidance for enhancing shale gas recovery by injecting CO₂.

中文翻译：

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表面成分对狭缝纳米孔中CH ₄和CO ₂微行为的影响：模拟探索

利用分子动力学模拟研究来研究CH ₄和CO ₂分子在具有不同表面和不同成分的狭缝纳米孔（SNP）中的微观行为。通过石墨烯，二氧化硅和方解石表面的成对组合来构造三种SNP。采用经典的蒙特卡洛方法和分子动力学模拟方法研究了纳米孔中气体的吸附和自扩散。发现在所有三种情况下，CH ₄分子都倾向于吸附在石墨烯表面上，而CO ₂则倾向于吸附在石墨烯表面上。分子更喜欢吸附在方解石表面上。计算了吸附在各种表面上的气体的吸附强度，吸附距离以及CH ₄和CO ₂分子在各种表面上的吸附取向的细节。分析表面特性，例如表面粗糙度和电荷分布，以帮助了解特定表面上气体的微观吸附行为。已经发现，由于CO ₂分子与方解石表面之间的强吸附相互作用，特别是在含方解石的SNP中，广泛发生了CO ₂在CH ₄上的竞争性吸附。这项工作提供了CH _{4的微行为}具有不同组成的不同表面的SNP中的CO2和CO ₂，为更好地了解复杂的纳米多孔页岩形成中的气体微观状态提供了有用的指导，并为通过注入CO ₂增强页岩气的采收率提供了有用的指导。