Insights into Carbon Dioxide Hydrate Nucleation on the External Basal Surface of Clay Minerals from Molecular Dynamics Simulations

CO2 hydrate nucleation on the surfaces of clay minerals is important because it is related to CO2 storage in marine sediments. In this study, heterogeneous nucleation of CO2 hydrates on the external surfaces of clay minerals (montmorillonite, illite, kaolinite, chlorite, and talc) was investigated using molecular dynamics simulations. The results showed that hydrate nucleation occurred far away from the surfaces of montmorillonite and illite. No hydrate nucleation occurs on the siloxane surface of kaolinite and talc due to the formation of CO2 nanodroplets. Of particular interest is that the clathratelike structures formed on the siloxane surface of chlorite due to its electric charge. Additionally, the clathratelike structures were also formed between the interfacial water and hydroxyl surfaces of kaolinite and chlorite. The results of this study clearly indicate that the surface groups of clay minerals significantly affect CO2 hydrate nucleation by changing the distribution of CO2 and water molecules, which finally influences CO2 storage in deposits and have profound impacts on related geochemical processes, such as interfacial interactions between water molecules and clay surfaces.