Gas Sensing Mechanism Studies On TiO₂ Nanotubes Detecting SF₆ Decomposed Components

Sulfur hexafluoride(SF6) is widely used in gas insulated switchgear(GIS) because of its excellent insulating and arc-extinguishing abilities. When partial discharge or overheating faults occur in the electrical equipment, which are usually caused by internal insulation defects, the gas-insulated SF6 may easily decompose and produce a variety of by-products with the inevitable trace H2 O and O2 in the gas chamber. The composition and content of these by-products can be used to determine the types, sizes, and causes of partial discharge and provide reliable information to evaluate the insulation status of the equipment. Presently, offline methods for detecting SF6 decompositions are effective, such as gas chromatography, mass spectrometry, and infrared spectrometry. Meanwhile, online monitoring methods still need further examination. Therefore, the Ti O2 nanotube array(TNTA) prepared using the anodic oxidation method is proposed as the sensor to detect the three characteristic decomposition components of SF6, which are SO2, SOF2, and SO2F2. This gas sensor is expected to be an effective online monitoring method. In this paper, the TNTA gas sensors for detecting SF6 decomposition components are studied through sensing experiment and theoretical calculation.In this paper, the anodic oxidation method is used to prepare the intrinst TNTA gas sensor. From the SEM, XRD, the intrinst TNTA is highly ordered, directional growth, pipe diameter for 80 nm around, pipe length for 300 nm. On this basis, Pt nanoparticles deposited in the Ti O2 nanotubes using the pulse electrochemical deposition method, and the Pt-doped TNTA is prepared. Then, the sensing performances of intrinst TNTA and Pt-doped TNTA are test, and the gas response temperature characteristics of them are studied and analyzed.Then, in order to have a fundamental understanding of interactions between gases and TNTA surfaces The adsorption behaviors of these gases on anatase(101) surface and(001) surface are studied using the first-principles DFT(Density Functional Theory) calculations to further explore the TNTA sensing on SO2, SOF2, and SO2F2. Given the possible occurrence of an oxygen vacancy, the surfaces include(101) perfect surface,(101) defect surface,(001) perfect surface, and(001) defect surface. The adsorptions of SO2, SOF2, and SO2F2 on Pt-doped anatase(101) surface are also calculated, the effect of doped Pt on the adsorption behavior of gas molecules is analyzed, and the sensing mechanism of Pt-doped TNTA is also explained clearly. The calculation results were analyzed to explain the results of intrinst and Pt-doped TNTA gas sensor sensing experiment. We improve the sensing mechanism of intrinst and Pt-doped TNTA and provide a theoretical basis for the detection of SF6 decomposition components using the TNTA gas sensor.