Molecular insights into hydrogen solubility in water under pore confinement

Abstract Underground hydrogen storage in geological formations has gained significant interest as a potential solution to global energy transition. Among the technical challenges related to underground hydrogen storage, one key fundamental problem is the solubility change due to the confinement, which is highly relevant to safety and efficiency. Though solubility enhancement has been extensively reported in multiple systems, hydrogen displays undersolubility under the nanoconfinement of clay. In this study, we use molecular dynamic simulations to study the hydrogen solubility in water at realistic storage conditions under the confinement of kaolinite. We find a solubility enhancement of 10-fold compared with that in the bulk for both hydrophobic and hydrophilic systems. Furthermore, we identify the major driving mechanism and show that the over-solubility is driven by adsorption and confinement.