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 the pha-graphene at different metal densities, temperatures, and pressures. It is demonstrated that the optimum adsorbent location of the Li atom 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 different density 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-25 kJ/mol. The GCMC results at different pressures and temperatures show that with the increase of Li decorative density, the hydrogen storage gravimetric ratio of pha-graphene decreases but can reach the standard of 2025 DOE (5.5 wt%). Therefore, pha-graphene is considered as a potential hydrogen storage material.