Capacity enhancement of polylithiated functionalized boron nitride nanotubes: an efficient hydrogen storage medium

By using first principles density functional theory simulations, we report detailed geometries, electronic structures and hydrogen (H₂) storage properties of boron nitride nanotubes (BNNTs) doped with selective polylithiated molecules (CLi₂). We find that unsaturated bonding of Li-1s states with BNNT significantly enhances the system stability and hinders the Li-Li clustering effect, which can be detrimental for reversible H₂ storage. The H₂ adsorption mechanism is explained on the basis of polarization caused by the cationic Li⁺ of CLi₂ molecules bonded with BNNT. The incident H₂ molecules are adsorbed with BNNT-nCLi₂ through electrostatic and van der Waals interactions. We find that with a maximum of 5.0% of CLi₂ coverage on BNNT, an H₂ gravimetric density of up to 4.41 wt% can be achieved with adsorption energies in the range of -0.33 eV per H₂, which is suitable for ambient condition H₂ storage applications.