Ab-initio investigations on titanium (Ti) atom-doped divacancy monolayer h-BN system for hydrogen storage systems

Abstract

This study demonstrates the hydrogen (H) storage process on titanium (Ti) atom doped divacancy (DV) hexagonal boron nitride (h-BN) system using first-principles density functional theory (DFT). Two configurations were adopted for H storage on the h-BN system. In first approach, H2 molecules were adsorbed on one side and in second approach H2 molecules were adsorbed on both sides of the Ti-atom substituted DV h-BN system. The binding energies of each system for both of these adsorption approaches were calculated, and it was revealed that the system having H2 molecules adsorbed on both sides of h-BN layer produce improved binding energy in comparison to single sided H2 adsorption on Ti decorated h-BN layer. These findings suggest that storing H2 molecules on double sides of Ti-atom substituted DV h-BN system is a preferred approach in comparison to single sided adsorption. The electronic and magnetic properties of H2 adsorbed Ti atom substituted DV BN complexes were also calculated. Further, spin-polarized band structure analysis suggested that the H2 adsorption along with Ti atom substitution at DV site converts insulating h-BN material to a narrow band semiconducting material. In addition, the difference in gap opening during positive and negative spin is substantial making it viable for spintronic applications. The obtained band gap values were in the range of 1–2.5 eV for different H2-adsorbed Ti atom substituted DV h-BN systems respectively. Also, the H2-molecule adsorption on Ti atom substituted DV h-BN system introduces finite magnetic moments ranging up to 2.00 μB, thus producing a magnetic h-BN material by nature. The density of states (DOS) plots were generated to observe the origin of magnetism and orbital occupation. It is observed that the d orbitals of Ti atom mainly attribute to the magnetic behavior of DV h-BN system. The results of this study establish that Ti atom-doped DV h-BN system is geometrically stable and it can provide higher hydrogen storage capability.