Molecular Dynamics of Carbon Sequestration via Forming CO2 Hydrate in a Marine Environment

The current situation of global warming requires immediate attention due to the excessive accumulation of CO2 in the atmosphere. Given that the hydrate generation process can trap CO2 molecules in the lattice of water molecules, it could be a promising strategy to store CO2 in the ocean as hydrates. In this paper, molecular dynamics (MD) simulations are used to investigate the behavior of CO2 hydrate growth in salt-containing electrolyte solutions, and the mechanism of the effect of thermodynamic conditions and salt ions on hydrate growth is explored. The simulation results show that a proper subcooling can promote the hydrate growth process, yet the fluctuation of the hydrate growth rate is still significant in the presence of salt ions. Higher temperatures and salt ions both inhibit the formation of hydrogen bonds between water molecules, reducing the possibility of cage structure formation. Notably, the saline environments enhanced the competition for water molecules between hydrate cages and salt ions, increasing the proportion of empty cages. The selectivity of CO2 molecules to enter different cages is influenced by both the temperature and salt ions; higher temperatures and the presence of salt ions make it more difficult for CO2 molecules to enter the smaller 512 cages. The results of the study provide insights into the mechanism of CO2 hydrate generation in seawater at the microscopic level, guiding the future realization of CO2 sequestration technology via forming hydrate in marine environment.