Hexagonal boron nitride (h-BN) nanosheet as a potential hydrogen adsorption material: A density functional theory (DFT) study

The hydrogen storage capacity of Boron Nitride nanosheet has been performed by using density functional theory (DFT). All the structural and electronic properties of a monolayer BN nanosheet are in well agreement with the previously reported results. Out of the four possible adsorption sites, centre is the most favourable adsorption site for H-2 molecule with binding energy similar to 0.212 eV/H-2. We have proceeded our calculations considering this adsorption site. The calculated direct band gap within GGA and HSE for pristine h-BN monolayer are found to be 4.669 eV and 5.63 eV, respectively. In our calculation the Hydrogen storage capacity of BN nanosheet was found to be 6.7 wt.% well within benchmark value (6.0%) with an average adsorption energy of (similar to 0.128 eV/H-2). Bader analysis revealed that the charge transfer from BN nanosheet to the H-2 molecule is very low (0.004-0.065 vertical bar e vertical bar) leading to weak binding of the H-2 molecule. The calculated desorption temperature was found to be low due to low average adsorption energy of the H-2 molecule. Also, upon increasing the number of H-2 molecule adsorption a feeble tuning of the band gap has been observed due to the contribution of the 1s orbital of H-2 molecule.