Hydrogen physisorption in earth-minerals: Insights for hydrogen subsurface storage

Physisorption can contribute to hydrogen subsurface storage. However, hydrogen physisorption at the surface of geological samples is mostly unknown. We are unaware of previous studies that investigate H₂ Physisorption in wide range of pure inorganic and organic earth minerals. Knowledge about H₂ Physisorption is required to evaluate the suitability of underground H₂ storage. We thus evaluated H₂ physisorption on common earth minerals, including illite, kaolinite, quartz, calcite, and kerogen via lab experiments and Grand Canonical Monte Carlo (GCMC) simulations at temperature ranging between 273 and 373 K and pressure ranging between 5 MPa to 40 MPa. The simulation results, including densities and H₂ adsorption uptakes, are in agreement with experimental results. The quantity of adsorbed hydrogen ranked as: illite > kerogen > kaolinite > quartz > calcite; and Gibbs energy change, enthalpy change, and isosteric heat energy indicated that H₂ adsorption spontaneity increases as illite > kerogen > kaolinite > calcite > quartz. We conclude that H₂ adsorption is high on the high-surface-area materials (clays or kerogen), and that H₂ adsorption on earth minerals could improve the effectiveness of subsurface H₂ storage.