Grand canonical Monte Carlo simulation study of hydrogen storage by Li-decorated pha-graphene

Abstract

Grand canonical Monte Carlo simulation (GCMCs) is utilized for studying hydrogen storage gravimetric density by pha-graphene at different metal densities, temperatures and pressures. It is demonstrated that the optimum adsorbent location for Li atoms is the center of the seven-membered ring of pha-graphene. The binding energy of Li-decorated pha-graphene is larger than the cohesive energy of Li atoms, implying that Li can be distributed on the surface of pha-graphene without forming metal clusters. We fitted the force field parameters of Li and C atoms at different positions and performed GCMCs to study the absorption capacity of H2. The capacity of hydrogen storage was studied by the differing density of Li decoration. The maximum hydrogen storage capacity of 4Li-decorated pha-graphene was 15.88 wt% at 77 K and 100 bar. The enthalpy values of adsorption at the three densities are in the ideal range of 15 kJ⋅mol−1–25 kJ⋅mol−1. The GCMC results at different pressures and temperatures show that with the increase in Li decorative density, the hydrogen storage gravimetric ratio of pha-graphene decreases but can reach the 2025 US Department of Energy’s standard (5.5 wt%). Therefore, pha-graphene is considered to be a potential hydrogen storage material.