Molecular Insight into hydrogen storage of H2 + CH4 sII hydrates

Abstract

We performed first-principles calculations and simulations to investigate the hydrogen storage properties of binary hydrates formed by H₂ and CH₄. The results showed that the optimum hydrogen storage capacity ranged from 3.43 wt% to 5.42 wt%, and the high storage capacity could be achieved by tuning cage occupation of CH₄ in 5¹² or 5¹²6⁴ cages. Further, two binary hydrate structures (denoted as T1 and T2) were chosen to assess the effect of pressure and temperature on the hydrate stability. Simulation results showed that two hydrates were stable at the studied conditions (10–30 MPa, and 260–285 K). At high pressures (more than 20 MPa) T1 structure was stable, while at low pressures T2 structure was stable. More importantly, H₂ + CH₄ binary hydrates exhibit anomalous stability at about 275 K, which would be helpful for the application of hydrate-based hydrogen storage technology under mild conditions.