Gas-sensing mechanism of two-dimensional MoSe2-Based composites for characteristic gases in environmentally friendly insulation equipment

Air insulated switchgear (AIS) is the core equipment for ensuring the safe and stable operation of power grids. Internal insulation defects will directly endanger the operational safety of power grid facilities. Detection of the concentrations of fault characteristic gases such as CO and NO 2 inside AIS provides a feasible method for monitoring internal partial discharge in the equipment. As a typical transition metal dichalcogenide (TMD), MoSe 2 possesses a suitable band gap structure and excellent chemical stability, making it an ideal substrate for fabricating high-performance gas sensors. Pure MoSe 2 exhibits only weak van der Waals adsorption toward CO and NO 2 (adsorption energies of −0.0923 eV and −0.115 eV, charge transfer of −0.0181 e and −0.1582 e, respectively), which can hardly meet the requirements of practical gas-sensing detection. Based on density functional theory (DFT), this work systematically investigates the adsorption behavior and gas-sensing mechanism of MoSe 2 composites doped with three metal oxides: ZnO, SnO 2 and CoO. The results demonstrate that metal oxide doping effectively introduces active sites and modulates the electronic structure, significantly enhancing the adsorption strength and gas-sensing performance of the material. Specifically, ZnO–MoSe 2 yields adsorption energies of −1.04 eV (CO, charge transfer 0.1105 e) and −3.81 eV (NO 2 , charge transfer −0.1732 e), and is suitable for recyclable CO detection and NO 2 capture; SnO 2 –MoSe 2 shows adsorption energies of −0.191 eV (CO, charge transfer 0.0944 e) and −0.994 eV (NO 2 , charge transfer −0.2052 e), and enables recyclable NO 2 detection; and CoO–MoSe 2 shows the highest sensitivity (sensing response of 55.106 toward NO 2 ) and optimal selectivity to NO 2 with an adsorption energy of −1.71 eV and charge transfer of −0.1356 e, with reversible desorption and cyclic regeneration achievable by heating, making it the preferred gas-sensitive material for NO 2 detection in environment-friendly insulation equipment. This study provides a theoretical basis and material design strategy for developing high-sensitivity and reusable gas sensors for environment-friendly medium- and high-voltage equipment.