CO
2 capture and geological sequestration have been considered important strategies to reduce the greenhouse gas effect. Meanwhile, H
2 produced from water using renewable energy and stored underground will be important components in a H
2 supply chain in a future H
2-based economy. When injected into a reservoir, gas interacts with earth materials that might impact the safety and economic feasibility of a storage. In this talk, we will discuss gas intercalation into smectite that is present in caprock. Intercalation traps CO
2, thus improving CO
2 storage integrity. However, intercalation causes H
2 loss. Using molecular dynamics (MD) simulation, we calculate free energy landscapes of gas intercalation into montmorillonite interlayers as a function of structural charge distributions and interlayer hydration states. Our results reveal that hydrated clay interlayers promote gas uptake into the hydrophobic (e.g., siloxane groups) domain, while inhibiting gas sorption near the hydrophilic sites (e.g., charge sites). On average, the CO
2/water ratio in interlayers is higher than CO
2/water ratio in bulk water. However, H
2/water ratio in interlayers is comparable or less than H
2/water ratio in bulk water. Compared to CO
2, the amount of H
2 intercalated into hydrated interlayers is about one to two orders of magnitude smaller. Our results qualitatively predict that H
2 loss due to intercalation into clay-rich caprock and leak through clay interlayers, if any, is limited.
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energyâs National Nuclear Security Administration under contract DE-NA0003525.
