Gas-Sensing Performance of Metal Oxide Heterojunction Materials for SF 6 Decomposition Gases: A DFT Study.

The online monitoring of GIS equipment can be realized through detecting SF 6 decomposition gasses. Metal oxide heterojunctions are widely used as gas-sensing materials. In this study, the structural and electrical properties of In 2 O 3 -ZnO and TiO 2 -ZnO heterojunctions were analyzed based on density functional theory calculations. After heterojunction structural optimization, the electrical conductivity of these two heterojunctions was enhanced compared to each intrinsic model, and the electrical conductivity is ranked as follows: In 2 O 3 -ZnO heterojunction > TiO 2 -ZnO heterojunction. The gas-sensing response of these two heterojunctions to four SF 6 decomposition gasses, H 2 S, SO 2 , SOF 2 , and SO 2 F 2 , was investigated. For gas adsorption systems, the adsorption energy, charge transfer, density of states, charge difference density, and frontier molecular orbitals were calculated to analyze the adsorption and gas-sensing performance. For gas adsorption on the In 2 O 3 -ZnO heterojunction surface, the induced conductivity changes are in the following order: H 2 S > SO 2 F 2 > SOF 2 > SO 2 . For gas adsorption on the TiO 2 -ZnO heterojunction surface, H 2 S and SOF 2 increase conductivity, and SO 2 and SO 2 F 2 decrease conductivity.