Ultrahigh capacity and reversible hydrogen storage media based on Li-decorated T-BN monolayers

The hydrogen storage performance of Li decorated BN monolayer (simply T-BN) composed of repeating octagons and tetragons (only including one element) were explored by using DFT+D calculations. The Li atoms are decorated steadily on the T-BN monolayer without any clustering, which has been confirmed by binding energy per Li (>2.68 eV), transition states search and phonon dispersion. H2 molecules interacting with the Li-decorated monolayer is of electrostatic nature. The Li-decorated T-BN monolayers have an ultrahigh hydrogen adsorption capacity of 12.31 wt% with adsorption strength of 0.245- 0.315 eV/H2, almost twice over the U.S. DOE target (6.5 wt%) and much larger than that of most of BN nanostructures. In addition, desorption temperature (TD), adsorption number of H2 at practical operating conditions, and MD simulations were studied to confirm the reversibility of the Li-decorated BN monolayers as hydrogen storage media. The TD for H2 at 1 atm is in the range of 180- 232.6 K, which would increase with the pressure increasing. In particular, the condition at 30 atm and under 200 K (or 3 atm and above 350 K) could be undoubtedly ideal adsorption (or desorption) condition, which is properly advantageous to the hydrogen-based fuel cell vehicle applications. Our findings thus reveal that the Li-decorated T-BN monolayers are extremely hopeful candidates for reversible and ultrahigh-capacity hydrogen storage media.