Hydrogen storage capacity in clay: An analytical model for storage density as a function of pore size, pressure, and temperature
Junfang Zhang, Regina Sander, Deasy Heryanto, Michael B. Clennell
Abstract
• Developed analytical model linking storage density to P, T and effective pore size. • Linear relationship between H 2 storage density and bulk density. • Estimation of theoretical H 2 storage capacity in smectite clay. • Excess hydrogen storage via adsorption ranges up to ∼15% in small pores (<5 nm). Clay minerals, abundant underground, maybe suitable for natural hydrogen storage and sealing. However, research on high-pressure hydrogen adsorption in clay under typical geological conditions has been limited. To address this, we conducted molecular dynamics simulations to investigate the effects of pressure, temperature, and pore size on hydrogen storage in clay-based materials like smectite. Simulations at temperatures from 308 to 400 K and pressures up to 259 MPa revealed that hydrogen adsorption is primarily governed by monolayer adsorption. We derived analytical expressions for bulk density and storage density (storage capacity normalized by pore volume) as functions of pressure, temperature, and pore size. Results indicate that the excess hydrogen storage by adsorption ranges from a few percent to over 15 %, with more storage enhancement being found in small pores, especially in interlayer space smaller than 5 nm across. Our models provide a framework for estimating the hydrogen storage capacity in clay formations.