Gas-Sensing Mechanism of Transformer Oil Dissolved Gases (CO, C₂H₄, CH₄) on the Pd-Modified Janus SnSSe Monolayer: A Density Functional Theory Study

This study investigates the gas sensing properties of the Pd-modified Janus SnSSe monolayer for transformer oil dissolved gases (CO, C₂H₄, and CH₄) using density functional theory (DFT). The results demonstrate that the incorporation of Pd metal atom onto the S and Se sites of the SnSSe monolayer significantly enhances their adsorption capabilities while maintaining structural stability. By analyzing key parameters such as adsorption energy, adsorption distance, charge density, density of states, orbital theory, recovery time, sensitivity, and work function, the adsorption behavior and sensing mechanisms of various gas systems are thoroughly examined. The analysis reveals that the intrinsic SnSSe monolayer is not suitable for detecting the three gases and exhibits a physical adsorption interaction. In contrast, the Pd-modified SnSSe(S)/SnSSe(Se) monolayer shows enhanced adsorption energies of -0.979, -0.740, and -0.099 eV for CO, C₂H₄, and CH₄, respectively, with corresponding values of -1.120, -0.786, and -0.112 eV for the SnSSe(Se) system. At the optimal working temperature, the Pd-SnSSe(S)/CO system exhibits a recovery time of 60.75 s, while the Pd-SnSSe(Se) system shows recovery times of 31.58 s for CO and 19.63 s for C₂H₄, respectively. Both materials demonstrate poor adsorption for CH₄. This work provides theoretical insights into the development of low-power, high-sensitivity, and fast-response gas sensors for detection of transformer oil dissolved gases.