Hydrogen storage in sH binary hydrate: Insights from molecular dynamics simulation

Abstract

sH hydrate is a kind of hydrate that is consisted of only organic large molecule and water. Since each organic large molecule can bring five small cages that easily capture hydrogen molecules, sH hydrate is potential hydrogen storage material. In this paper, methylcyclohexane-hydrogen hydrate was used for hydrogen storage. Two different processes, the simultaneous formation and the induced formation, were studied by molecular dynamics simulation. The simultaneous formations of methylcyclohexane-hydrogen binary hydrate were simulated at 230 K & 110 MPa and the hydrogen storage capacity of binary hydrate was 1.08 wt%. The induced formation of methylcyclohexane-hydrogen binary hydrate was simulated at 240–260 K &20–110 MPa.The simulation results showed that hydrogen storage capacity of hydrate was mainly affected by temperature. The hydrogen storage capacity of hydrates was low (≤1.0 wt%) at 250–260 K even the pressure increased to 110 MPa. While the hydrogen storage capacity was greatly improved (≥1.6 wt%) at 240 K. At 250–260 K, hydrogen molecules only entered the cavities that were near the interface, which seems that 512 cages layers obstructed the hydrogen molecules. The results indicated that the induced hydrogen formation required milder conditions than the simultaneously hydrogen storage formation, and the hydrogen storage was higher.