Low hydrogen solubility in clay interlayers limits gas loss in hydrogen geological storage

Abstract

Gas intercalation into clay interlayers may result in hydrogen loss in the geological storage of hydrogen; a phenomenon that has not been fully understood and quantified. Here we use metadynamics molecular simulations to calculate the free energy landscape of H₂ intercalation into montmorillonite interlayers and the H₂ solubility in the confined water; in comparison with results obtained for CO₂. The results indicate that H₂ intercalation into hydrated interlayers is thermodynamically unfavorable while CO₂ intercalation can be favorable. H₂ solubility in hydrated clay interlayers is in the same order of magnitude as that in bulk water and therefore no over-solubility effect due to nanoconfinement is observed – in striking contrast with CO₂. These results indicate that H₂ loss and leakage through hydrated interlayers due to intercalation in a subsurface storage system, if any, is limited.