Adsorption Properties of Metal Oxides (ZnO, TiO 2 , Ag 2 O) Modified SnS 2 Toward Dissolved Gas Analysis in Transformer Oil

In this study, the gas-sensing mechanism of ZnO, TiO2, and Ag$_{{2}}\text{O}$modified SnS2 toward dissolved gases (CO, CH4,$\text{C}_{{2}}\text{H}_{{2}}$, and$\text{C}_{{2}}\text{H}_{{4}}{)}$in transformer oil was studied based on the density functional theory (DFT). The modified structure, adsorption structure, band structure, adsorption energy, charge transfer, deformation charge density (DCD), density of states (DOSs), and molecular orbit were analyzed. The results show that the conductivity of SnS2 monolayer is improved to a certain extent after surface modification with ZnO, TiO2, and Ag$_{{2}}\text{O}$. Also, the adsorption of CO, CH4,$\text{C}_{{2}}\text{H}_{{2}}$, and$\text{C}_{{2}}\text{H}_{{4}}$on the intrinsic SnS2 monolayer is weak physical adsorption. Compared with the intrinsic substrate, the adsorption energies of MO–SnS2 (M = Zn, Ti, Ag$_{{2}}{)}$monolayer for the four target gases have been increased to different degrees, except that the adsorption energy of TiO2–SnS2 for$\text{C}_{{2}}\text{H}_{{4}}$molecule has decreased slightly. With DCD, DOSs, and molecular orbital analysis, it can be concluded that ZnO–SnS2 and TiO2–SnS2 have good gas sensitivity to CO,$\text{C}_{{2}}\text{H}_{{2}}$, and$\text{C}_{{2}}\text{H}_{{4}}$molecules, and Ag$_{{2}}\text{O}$–SnS2 also has strong adsorption capacity to$\text{C}_{{2}}\text{H}_{{2}}$and$\text{C}_{{2}}\text{H}_{{4}}$molecules. This work provides a theoretical basis for the application of gas sensors used in oil-immersed transformers.