Hydrate-based CO2 storage in the ocean is
considered
a potential method for mitigating the greenhouse effect. Numerous
studies demonstrated that NaCl exhibited the dual effects of promotion
and inhibition in the nucleation and growth processes of CO2 hydrate, whose mechanisms remain unclear. In this study, the effects
of NaCl at various concentrations on the CO2 hydrate growth
and crystal are investigated. The independent gradient model based
on Hirshfeld partition, electrostatic potential, and binding energy
is conducted to study the interaction between ions and water molecules.
The motion trajectories of ions are observed at the molecular level
to reflect the impact of ion motion on hydrate growth. The results
show that the influence of NaCl on hydrate growth depends on a delicate
balance of dual promotion–inhibition effects. NaCl can combine
more water molecules and provide a transport channel of CO2 to promote hydrate growth at low concentrations. Meanwhile, the
promoting effects shift toward inhibition with increasing NaCl concentrations.
In a word, this paper proposes a novel mechanism for the dual promotion–inhibition
effects of NaCl on hydrate growth, which is significant for further
research on hydrate-based CO2 storage in the ocean.