Low Barrier Interface of NiO-Ti₃C₂O₂ for Sulfur Hexafluoride Decomposition Gas-Sensing Application: A DFT Study

As an insulating medium in electrical equipment, the accurate detection of sulfur hexafluoride (SF₆) decomposition products (H₂S, SO₂, SOF₂ and CO) caused by insulation faults is crucial for safe operation of equipment. Although the intrinsic two-dimensional material Ti₃C₂O₂ exhibits affinity toward target gases, its adsorption performance remains limited. To enhance its gas-sensing properties, this study proposes and systematically investigates, based on first-principles calculations, an interface engineering strategy in which NiO-modified Ti₃C₂O₂ forms a heterojunction with a low-barrier pseudo-Ohmic contact. Through comprehensive calculations of adsorption configurations, band structure, adsorption energies, charge transfer, density of states (DOS), electron density difference (EDD), and desorption times, the enhancement mechanism induced by NiO modification has been elucidated. The results show that (1) NiO modification introduces highly active sites into Ti₃C₂O₂, significantly promoting interfacial charge transfer. (2) All four gases can be spontaneously adsorbed onto NiO-Ti₃C₂O₂, with adsorption energies of -1.855, -1.634, -0.993, and -0.785 eV for CO, SO₂, H₂S, and SOF₂ respectively, indicating that the adsorption strength follows the order CO > SO₂ > H₂S > SOF₂. (3) Desorption-time analysis indicates that the material holds potential for rapid response toward H₂S and SOF₂, while exhibiting strong capture capability for SO₂ and CO at room temperature, suggesting its dual application prospects in high-sensitivity detection and removal.