Adsorption and Gas Sensing Properties of h-BN/WS2 Heterojunction for Toxic Gases: A DFT Study

Tungsten disulfide (WS₂) and hexagonal boron nitride (h-BN) monolayer, and h-BN/WS₂ heterojunction with low lattice mismatch is constructed using density functional theory (DFT). The band structures, density of states (DOS), charge density differences (CDD), work function (WF), adsorption energy and adsorption distance of h-BN/WS₂ heterojunction for six gases molecules (CO, CO₂, NO, NO₂, SO₂, and H₂S) are systematically discussed. Gas adsorption on one-side and both-sides of the heterojunction is considered. The results indicate that the band gap of the heterojunction is lower than that of h-BN and WS₂, indicating that the construction of heterojunction is beneficial for conductivity. For six gases, the adsorption energy of one-sided adsorption is significantly greater than that of both-sided adsorption, except for CO₂ and NO. The adsorption of NO and NO₂ introduces the magnetism into the system. Interestingly, the h-BN/WS₂ heterojunction demonstrates excellent selectivity for NO gas under one-sided and both-sided adsorption. The corresponding adsorption mechanism is explored.