Adsorption of Gas Molecules on HfSSe Janus Monolayer

The density functional theory (DFT) method have already been used to study the electronic, optical and the adsorption properties of (CO, CO2, NO, NO2, SO2) gas molecules on HfSSe (Se and S) monolayer. Initially, the properties of pristine HfSSe monolayer are calculated. The band gap of HfSSe (Se and S) monolayer is estimated to be 0.626eV which authorize the semiconducting behavior. The results show that the adsorption of gases occurs at different sites on the studied monolayer. However, every the adsorption energies are negatives and the adsorption of gas molecules on this monolayer undergoes physisorption interaction, thus they can be used to detecting gas molecules. The refractive indices of HfSSe-S monolayer are larger than that in HfSSe-Se monolayer, and reach to 2.50 and 2.31 of CO2 and SO2gases, approximately. On the opposite, the reflection peaks of the monolayer occur in the UV region range which agrees with the absorption coefficient. Besides, the maximum value of reflectivity in the adsorbed systems does not exceed 60%.