Adsorption of CO and SO2 on SnS monolayer doped with transition metal oxides (TiO2, CuO, and NiO): A DFT study

Abstract

Industrial emissions, particularly CO and SO2, pose significant threats to both the ecological environment and human health, highlighting the critical need for online monitoring and the removal of these harmful gases. Based on density functional theory, this study explores the adsorption mechanisms of CO and SO2 on SnS monolayer doped with transition metal oxides (TiO2, CuO and NiO), analyzing geometric structures, band structures, state densities, work functions, and molecular orbitals. The findings reveal that transition metal oxides significantly alter the surface activity of SnS, with TiO2 doping and CuO doping reducing the band gap by 9.37% and 39.05%, respectively, and NiO doping increasing the band gap by 4.60%. CuO-SnS and NiO-SnS demonstrate robust physicochemical adsorption capabilities for CO and SO2, while TiO2-SnS displays certain physical adsorption properties. Following the adsorption of SO2, CuO-SnS and NiO-SnS exhibit the most significant changes in work function, increasing by 18.37% and 7.55%, respectively. The adsorption of CO and SO2 significantly alters the LUMO and HOMO levels, as indicated by molecular orbital analysis, suggesting that the changes in electrical conductivity post-adsorption facilitate accurate differentiation of gas types. The findings indicate that SnS doped with transition metal oxides (TiO2, CuO and NiO) hold potential as gas-sensitive sensing materials suitable for the online monitoring of CO and SO2.