First-principles study of NO adsorption on defective hexagonal boron nitride monolayer

This study explored the potential of hexagonal boron nitride (h-BN) as a support for selective catalytic reduction (SCR) which means converting NO_x to N₂ and H₂O with the aid of a catalyst. Specifically, we investigated the adsorption behavior of a NO molecule on a defective h-BN monolayer using density functional theory. Our results indicated that the initial configuration of N and O atoms over vacancy defects plays a key role in determining whether the NO molecule is adsorbed on the h-BN monolayer via covalent or ionic bonding. In the case of mono-vacancy, the O–N configuration of the NO gas resulted in lower total energy (E_total) compared with the N–O configuration. Furthermore, electron localization function and Bader charge analysis, as well as projected density of states, revealed that the O–N configuration over B or N vacancy resulted in chemisorption by hybridizing p-orbitals. Furthermore, the di-vacancy system led to an even lower E_total compared with the mono-vacancy case. In particular, both N and O atoms were adsorbed chemically to the edge of vacancy defects, irrespective of the NO configurations above the di-vacancy. Our calculations revealed that the presence of vacancy defects contributed to improving the adsorption of the NO molecule to the h-BN monolayer.