Anti-Kubas Type Interaction in Hydrogen Storage on a Li Decorated BHNH Sheet: A First-Principles Based Study

We have performed first-principles DFT calculations to explore the possibility of using a metal-functionalized hydrogenated BN sheet for storage of molecular hydrogen. The chair BHNH conformer is ideally suited for adsorption of metal adatoms on the surface of the sheet. The Li metal, in particular, binds to the sheet with a binding energy (similar to 0.88 eV/Li atom) and becomes cationic, which thereby attracts hydrogen molecules. However, the interaction of the BHNH sheet and the absorbed H-2 molecules with Li+ is different from the conventionally known Dewar coordination or Kubas-type interaction for hydrogen storage. Each Li+ can adsorb up to four H-2 molecules, and the hydrogen binding energy is in the desired energy window for effective storage of molecular hydrogen. The fully Li-functionalized BHNH sheet yields a reasonably high gravimetric density, which is more than 7 wt %.