Abstract
Hydrogen (H2) storage holds significant promise in facilitating the energy transition and mitigating the energy crisis and greenhouse effect. A thorough understanding of H2 storage and transport mechanisms is a prerequisite for advancing H2 energy applications such as underground H2 storage and natural H2 exploration. Clay minerals, abundant in reservoirs and caprocks, play a key role in gas adsorption and diffusion, influencing the behavior and fate of H2 in the subsurface. We conducted H2 isothermal adsorption and kinetic experiments on montmorillonite and sepiolite at 30 °C, 40 °C, and 50 °C over the pressure range of 0–9.8 MPa to investigate the modeling, kinetics, and diffusion of H2 adsorption behavior in clay minerals. The Langmuir, Freundlich, Sips, Temkin, Toth, Brunauer-emmett-teller (BET) and Dubinin-Astakhov (DA) models were used to fit the equilibrium data, while the pseudo-first-order, pseudo-second-order, and Bangham models analyzed adsorption kinetics. The stretched exponential model characterized diffusion properties. Results indicated that the BET model presents the best fitting results to the adsorption isotherms at different temperatures. The Bangham kinetic model can satisfactorily predict the experimental kinetics data at various pressure stages for the entire time range. Higher temperatures and pressures lead to a decrease in the Bangham adsorption rate constant. The Bangham adsorption rate constant and diffusion coefficient for sepiolite are significantly higher than those for montmorillonite. The H2 diffusion coefficient in clay minerals decreases with increasing pressure. These findings highlight sepiolite's high adsorption capacity and its potential impact on the fate of H2 in geological environment.