Selenium Vacancy–Enhanced Gas Adsorption of Monolayer Hafnium Diselenide (HfSe 2 ) from a Theoretical Perspective

The gas adsorption properties of monolayer selenium vacancy–defective (V Se ) hafnium diselenide (HfSe 2 ) compared with that of pure monolayer HfSe 2 for CO, NO, NO 2 , SO 2 , CO 2 , H 2 O, H 2 S, and NH 3 molecules are theoretically investigated using density functional theory (DFT) based on first‐principle calculations. The equilibrium distance, adsorption energy, charge transfer, and electron localization function of pure and Se vacancy–defective HfSe 2 (V Se ‐HfSe 2 ) monolayers with absorbed gases are systematically calculated. It is demonstrated that monolayer V Se ‐HfSe 2 exhibits enhanced adsorption energy and charge transfer than that of pure HfSe 2 , and the band structures reveal that the adsorption of CO, NO, NO 2 , and SO 2 molecules can significantly modify the electronic structure of V Se ‐HfSe 2 monolayer. In addition, the atom projected density of states suggests the existence of orbital hybridization between the gas molecules, and V Se ‐HfSe 2 is the primary cause of high charge transfer. The results demonstrate that selenium vacancy will effectively enhance the gas adsorption ability for HfSe 2 monolayer, especially for CO, NO, NO 2 , and SO 2 molecules.