Superalkali NLi4 decorated graphene: A promising hydrogen storage material with high reversible capacity at ambient temperature

Abstract

This paper investigates the decoration of superalkali NLi4 on graphene and the hydrogen storage properties by using first principles calculations. The results show that the NLi4 units can be stably anchored on graphene while the Li atoms are strongly bound together in the superalkali clusters. Decoration using the superalkali clusters not only solve the aggregation of metal atoms, it also provide more adsorption sites for hydrogen. Each NLi4 unit can adsorb up to 10 H2 molecules, and the NLi4 decorated graphene can reach a hydrogen storage capacity 10.75 wt% with an average adsorption energy −0.21 eV/H2. We also compute the zero-point energies and the entropy change upon adsorption based on the harmonic frequencies. After considering the entropy effect, the adsorption strengths fall in the ideal window for reversible hydrogen storage at ambient temperatures. So NLi4 decorated graphene can be promising hydrogen storage material with high reversible storage capacities.