Sensitive and Reversible Detection of SF6 Decomposition Gases in GIS: A DFT Study of Pd/Pt-Modified Mo2TiC2O2

This work systematically investigates the adsorption behaviors and gas-sensing performances of Pd and Pt single-atom modified Mo2TiC2O2 toward SF6 decomposition gases (H2S, SO2, SOF2, and SO2F2) using first-principles calculations. Key parameters including adsorption energy, charge transfer, density of states, band structure, molecular orbitals, work function, and recovery time are calculated. Pd and Pt favor the hollow and bridge sites, respectively. Both substrates exhibit the strongest adsorption toward H2S (-1.440 to - 1.644 eV), but the excessively long recovery times at room temperature preclude reversible detection. SO2 and SOF2 show moderate adsorption energies (-0.964 to -1.157 eV) with considerable charge transfer, and their recovery times reach the second-to-millisecond scale at 398-498 K. SO2F2 exhibits the weakest adsorption and response. Electronic structure analyses reveal that Pd/Pt modification opens a small band gap (0.019-0.055 eV) in the metallic pristine substrate; H2S and SO2 further reduce the gap (Pt-H2S reaching 0 eV), whereas SO2F2 widens it. Work function and orbital distributions confirm the electron donor/acceptor behavior and hybridization differences among gases. Considering all factors, SO2 and SOF2 are the most suitable target gases with a recommended operating temperature of 398-498 K. This study provides a theoretical basis for single-atom modified MXene-based gas sensors.