Molecular Insights into Geochemical Reactions of Iron-Bearing Minerals: Implications for Hydrogen Geo-Storage

H Lee and RY Zheng and LL Huang and TC Germann and MR Gross and M Mehana, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, 13, 4548-4559 (2025).

DOI: 10.1021/acssuschemeng.4c10515

This study investigates the reaction of hydrogen (H-2) with pyrite (FeS2), focusing on how temperature and the presence of water influence the reaction pathways and kinetics. Utilizing computational molecular simulations and kinetic analyses, we explore the impact of these factors on the formation of hydrogen sulfide (H2S) and related species. First, grand canonical Monte Carlo/molecular dynamics (GCMC/MD) simulations reveal that physical H-2 adsorption occurs in distinct layers on the pyrite surface. In addition, increased temperatures reduce the absolute adsorption capacities. Reactive MD simulations demonstrate that H-2 interacts differently with pyrite under varying conditions. At 298 K, H-2 reacts with pyrite to form HS-, leading to the formation of HS- through covalent bonding with sulfur of pyrite. However, no H2S is produced at this temperature, suggesting that a kinetic barrier (i.e., activation energy) may prevent this reaction. At higher temperatures, H2S production significantly increases. The presence of water introduces additional complexity to the reaction mechanism. Unlike dry conditions, water enhances H2S generation, even at low temperatures. Water also facilitates the formation of additional products, such as SOH, indicating a more intricate chemical environment on the pyrite surface. Our findings identify the association of HS- ions to form H2S as the rate-limiting step, with temperature influencing this process. This finding suggests that while the presence of water can create a more dynamic reaction environment, the overall mechanisms leading to H2S formation remain consistent. These outcomes suggest the need for developing targeted strategies to manage and control H2S emissions within the context of underground hydrogen storage.

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