Structural and textural control of high-pressure hydrogen adsorption on expandable and non-expandable clay minerals in geologic conditions

Both natural and anthropogenically-generated hydrogen gas occurs in sedimentary rocks and geotechnical barriers. Due to high-pressure conditions, a significant portion of H-2 can be physisorbed in available micropores of clay minerals, which have been proven to control the gas adsorption properties of rocks. This study investigates H-2 adsorption on clay minerals naturally occurring in rocks, by combining the high-pressure H-2 experiments with sample characterization analyzed using low-pressure adsorption of N-2 and CO2, and structural analysis using X-ray diffraction. We found that H-2 adsorption depends strongly on the mineral texture, which is not related directly to its structure. Most of H-2 is adsorbed in the micropores accessible to CO2. H-2 intercalates in the smectitic interlayers with a basal spacing larger than 10.8 angstrom. The density of adsorbed H-2 is about double that of free H-2 gas under given pressure and temperature, effectively increasing the gas storage capacity of rocks. (C) 2022 The Author(s). Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.

Automated summary

This study investigates the adsorption of H-2 on clay minerals in rocks, revealing that the adsorption capacity depends on the mineral texture rather than its structure. The majority of H-2 is adsorbed in micropores accessible to CO2 and also intercalates in smectitic interlayers. This enhances the gas storage capacity of the rocks.