Radial deformation-induced high-capacity hydrogen storage in Li-coated zigzag boron nanotubes

We show that a Li-coated zigzag (2,2) boron nanotube can serve as a high-capacity hydrogen storage medium using first-principles density functional theory. The present results indicate that the radial deformation of a Li-coated boron nanotube can strengthen the binding of Li atoms to the boron nanotube due to the hybridization between Li-p orbitals and B-p orbitals. Interestingly, the induced large surface curvature of the Li-coated nanotube can make the H₂ molecules directly adsorbed on the nanotube. Through the electronic analysis we find that not only the polarization mechanism but also the orbital hybridization between H-s orbitals and Li-p (B-p) orbitals act on the adsorbed H₂ molecules. The Li-coated zigzag (2,2) boron nanotube reported here can store hydrogen up to 7.94 wt% with the adsorption energy of 0.12--0.20 eV/H₂ and the whole system is favorable for the reversible hydrogen adsorption/desorption at ambient conditions.