Reversible hydrogen storage and release mechanism of a B₂N monolayer: a first-principles insight

It was found the physical adsorption could be an efficient strategy for high capacity, high efficiency and high safety in hydrogen storage. In this research, a systematic investigation into the potential of the B₂N monolayer as an excellent physical adsorption hydrogen storage material is conducted by utilizing the first-principles calculation method. The findings of the investigation demonstrate that the B₂N monolayer has a planar lattice and excellent structural stability. It is possible for H₂ molecules to adsorb onto the B₂N monolayer spontaneously. Both the individual adsorption and saturation adsorption corresponded to average adsorption energies ranging from -0.221 to -0.194 eV, fulfilling the physical adsorption criteria. In the case of saturation adsorption, a 1 × 2 × 1 B₂N supercell can store a total of 24 H₂ molecules, with the hydrogen gravimetric density up to 14.511 wt% and volumetric density up to 138 g L^-1. A semi-empirical calculation method is used to research the performance of the system in terms of adsorption and desorption with actual temperature and pressure conditions. Under the actual conditions with adsorption carried out at 30 atm/233 K and desorption carried out at 3 atm/358 K, the maximal reversible hydrogen storage capacity of the hydrogen storage system based on the B₂N monolayer can still reach 12.157 wt%, which is superior to that of many other boron-nitrogen compounds and metal-free functionalized hydrogen storage materials. The findings of this work indicate that the pristine B₂N monolayer is one of the promising physical adsorption materials which could achieve excellent reversible hydrogen storage under defined conditions.