The adsorption capacity of intrinsic SnS2 to NH3, Cl2 and C2H2 is very weak. However, non-metallic elements B and N have strong chemical activity, which can significantly improve the conductivity and gas sensitivity of SnS2. Based on density functional theory, SnS2 was modified with B and N atoms to analyze its adsorption mechanism and gas sensitivity for NH3, Cl2 and C2H2 gases. The optimal structure, adsorption energy, state density and frontier molecular orbital theory are analyzed, and the results are in good agreement with the experimental results. The results show that the adsorption of gas molecules is exothermic and spontaneous. Only the adsorption of NH3 and Cl2 on B-SnS2 belongs to chemical adsorption, whereas other gas adsorption systems belong to physical adsorption. Moderate adsorption distance, large adsorption energy, charge transfer and frontier molecular orbital analysis show that gas adsorption leads to the change of the conductivity of the modified SnS2 system. The adsorption capacity of B-SnS2 to these gases is Cl2 > NH3 > C2H2. The adsorption capacity of N-SnS2 is NH3 > C2H2 > Cl2. Therefore, according to different conductivity changes, B-SnS2 and N-SnS2 materials can be developed for greenhouse gas detection of gas sensors.
Keywords: DFT; SnS2; adsorption; greenhouse gases; surface modification.