Molecular insights into the effect of storage pressure and water content on hydrogen behavior in a heterogeneous clay model with interconnected nanopores

In this study, a new molecular model of heterogeneous clay with interconnected micropores (<2 nm) was developed by assembling numerous Na-montmorillonite platelets, which provide a more realistic representation of geological environments than conventional models based on idealized channels. Comprehensive molecular simulations were then conducted to investigate the effects of storage pressure and water content on hydrogen adsorption and diffusion, with particular emphasis on quantifying hydrogen's spatial distribution across micropores. Results show that increasing storage pressure enhances hydrogen adsorption while suppressing hydrogen diffusion through intensified intermolecular collisions. Water strongly inhibits hydrogen adsorption by preferentially occupying adsorption sites, while interfacial water films and bridges among platelets block hydrogen diffusion. Additionally, hydrogen exhibits a distinct residence preference for micropores of specific sizes within the heterogeneous nanopore network. The results provide deeper insight into optimizing geological storage assessment and designing hydrogen-sealing barriers, thereby advancing sealing strategies in subsurface hydrogen storage.