Impact of hydration on hydrogen sorption in clay minerals and shale caprocks: Implications for hydrogen energy and waste storage

Understanding hydrogen sorption on clay minerals is crucial for hydrogen energy applications such as surface and subsurface storage, natural hydrogen exploration, and waste storage. However, safety issues surrounding hydrogen gas handling limit the availability of comprehensive data. This study investigates hydrogen sorption in various geomaterials, including four shale caprocks from the Norwegian Continental Shelf and three reference pure clay fractions. We have conducted thorough sample characterization, low-temperature nitrogen sorption, and high-pressure high-temperature hydrogen sorption tests on both dried and non-dried samples. The results highlight the higher hydrogen uptake capacity of swelling clays, particularly montmorillonite. Non-dried clay samples demonstrated reduced hydrogen sorption, likely due to competition between hydrogen and water for sorption sites within the clay structure. Freundlich, Langmuir, and Toth models were employed to analyze the experimental hydrogen isotherms, with the Freundlich model providing the best fit due to the linear or convex-downward nature of the isotherms. Based on our results, we suggest that in a fully water-saturated medium, the sorption of hydrogen on clay minerals is very low, and it is unlikely to significantly affect hydrogen transport. • 4 shale caprocks from the Norwegian Continental Shelf and 3 pure clays were studied. • HPHT hydrogen sorption tests were conducted on both dried and non-dried samples. • Non-dried samples demonstrated reduced hydrogen sorption. • Data from dried pure clay powders cannot be generalized to natural clay-rich rocks.