First-principles investigation of Irida-graphene decorated with alkali metal for reversible hydrogen storage

Irida-graphene (IG) is a novel stable graphene allotrope, which exhibits metallic property. Based on first principles calculations, the potential of IG decorated with alkali metal atoms in reversible hydrogen storage has been investigated. Compared with graphene, IG has stronger binding on alkali metal atoms. For Li, Na, and K decorated IG, the polarization mechanism plays a crucial role in the adsorption of H2, the adsorption energies of H2 are −0.286, −0.209 and −0.183 eV/H2, and the hydrogen gravimetric densities can reach 7.1, 7.8 and 5.2 wt%, respectively, indicating that K decorated IG is not suitable as a hydrogen storage medium. The desorption temperatures calculated are 365 K and 267 K for stored H2 on Li/IG and Na/IG, respectively, and ab inito MD simulation suggest that Li/IG and Na/IG are stable at high temperature, thus Li and Na decorated IG have the potential application for reversible hydrogen storage.