Comparison of Gas-sensitive properties of Au, Ag and Cu Metal-doped GaNNT for SF6 decomposition gases

Abstract

SF6 gas will produce various decomposition products When the partial discharge fault occurs in SF6 gas-insulated equipment, resulting in significantly reduced insulation performance of the insulated equipment. Early latent insulation faults in gas-insulated equipment can be diagnosed by monitoring the concentration of SF6 typical decomposition products (H2S, SO2, SO2F2 and SOF2) inside the insulated equipment. Gallium nitride nanotubes (GaNNT) have shown promising applications as gas-sensitive materials for sensors, and the gas-sensitive properties of the materials can be better improved by doped-metal. Therefore, the Density functional theory (DFT) calculation approach is proposed to compare with the gas-sensitive response characteristics of Au, Ag and Cu metal-doped GaNNT (M−GaNNT) to SF6 typical decomposition gases in the paper. The adsorption mechanism is analyzed by band structure, density of states, frontier molecular orbital theory and differential charge density, and the results are in high consistency. The metal-doped GaNNT introduces a large number of impurity bands which makes the probability of electrons crossing the forbidden band to reach the conduction band larger, and thus the gas-sensitive characteristics are improved. The adsorption of gases by M−GaNNT causes the resistivity of the system to vary, and sensing response (SR) and response time (RT) of M−GaNNT adsorbs gases are also analyzed. The results show that the ability of metal-doped GaNNT is Ag-GaNNT>Cu-GaNNT>Au-GaNNT, and the average values of SR are 516.9, 29.3 and 8.7, respectively. Ag-GaNNT has higher selectivity for SO2F2 gas. In summary, it shows that Ag-GaNNT is a potential gas-sensitive material that can be a new material for the online monitoring of fault gas content in gas-insulated equipment.