Li-decorated Pmmn8 phase of borophene for hydrogen storage. A van der Waals corrected density-functional theory study

Abstract

We performed standard and van der Waals-corrected density functional theory calculations to investigate the hydrogen storage capacity of a phase of borophene with Pmmn symmetry and nonzero thickness. This borophene sheet (Pmmn8) has 8 atoms in its unit cell and is more stable than the planar sheet and that the corrugated Pmmn2 sheet (2 atoms in the unit cell). Our results show that, in pristine form, the Pmmn8 sheet is not suited for hydrogen storage applications. However, decoration with Li atoms and strain increase the hydrogen storage ability of the sheet. We performed also a detailed quantum chemical topological analysis that shows that the B-Li interaction in the hydrogenated Li-decorated Pmmn8 sheet is ionic. Our results for the adsorption of H2 on the Li-decorated Pmmn8 sheet are compared with those obtained for the adsorption of H2 on Ti-decorated zigzag graphene nanoribbons.