Gas-Sensing Performance of Metal Oxide Heterojunction Materials for SF₆ Decomposition Gases: A DFT Study

The online monitoring of GIS equipment can be realized through detecting SF₆ decomposition gasses. Metal oxide heterojunctions are widely used as gas-sensing materials. In this study, the structural and electrical properties of In₂O₃-ZnO and TiO₂-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: In₂O₃-ZnO heterojunction > TiO₂-ZnO heterojunction. The gas-sensing response of these two heterojunctions to four SF₆ decomposition gasses, H₂S, SO₂, SOF₂, and SO₂F₂, 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 In₂O₃-ZnO heterojunction surface, the induced conductivity changes are in the following order: H₂S > SO₂F₂ > SOF₂ > SO₂. For gas adsorption on the TiO₂-ZnO heterojunction surface, H₂S and SOF₂ increase conductivity, and SO₂ and SO₂F₂ decrease conductivity.