Lithium decorated Ѱ-graphene as a potential hydrogen storage material: Density functional theory investigations

Abstract

In the present scenario, hydrogen has become a prominent alternative of fossil fuel that motivated us to develop more advanced nanomaterials to store efficient hydrogen for future use. This paper studies the hydrogen storage performance of Li-decorated Ѱ-graphene by conducting density functional theory simulations involving van der Waals corrections. Psi (Ѱ)-graphene is an advanced two-dimensional carbon allotrope that comprises pentagon, hexagon, and heptagon carbon rings. The simulation outcome reveals that the Li atom is bounded strongly to Ѱ-graphene with −2.63 eV binding energy through 0.89e charge transfer from Li-2s orbital to C-2p orbitals. Ѱ-graphene system decorated with the Li atom can bind seven hydrogen molecules with a suitable average binding energy of −0.31 eV/H2, high H2 gravimetric capacity of 15.15 wt%, and optimal average desorption temperature of 384 K. As per the Bader charge portioning, ∼0.09e charge is transferred from the Li-2s orbital to the H-1s orbital after hydrogen adsorption on Li + Ѱ-graphene. The hydrogen molecules are adsorbed on Li + Ѱ-graphene via a polarization mechanism. The high Li diffusion barrier of 0.78 eV and structural integrity of Li + Ѱ-graphene configuration at high temperature predicts that the system is a suitable candidate for high-capacity hydrogen storage applications.