Water-Lubricated CO2 and CH4 Transport in Crystalline Silica Mesopores: A Molecular Dynamics Study

In this study, we use molecular dynamics simulation to study slippage behaviors of pressure-driven CO₂ and CH₄ flows with water films in β-cristobalite mesopores. Significant differences in water-induced enhancement in gas slippage are observed in comparison to pure CO₂ and CH₄ flows: the presence of water films leads to a notable increase in slippage for CO₂ flow, whereas its effect on CH₄ flow is insignificant. The water films on surface generally deplete gas molecules. The density peak significantly decreases in the CO₂ adsorption layer, whereas the CH₄ adsorption layer shows a negligible density change. Water molecules tend to accumulate at the center of surface ring structures, forming strong hydrogen bonds with the surface hydroxyl groups parallel to surface. As a result, water molecules fill the interfacial roughness by squeezing out CO₂, which is supposed to penetrate into the ring structure. Therefore, CO₂-averaged topologically accessible planes are less curved, which enhances the mobility of the interfacial CO₂ molecules. However, CH₄-averaged topologically accessible planes show an insignificant change with water films. Consequently, CO₂ transport behaviors are more sensitive to the presence of water films on β-cristobalite surfaces. This study highlights the influence of water films on gas slippage, offering important insights into gas sequestration.