A first principles theoretical study of the adsorption of SF₆ decomposition gases on a cassiterite (110) surface

The detection of the identities and concentrations of sulfur hexafluoride, SF₆, decomposition products is important for evaluating the conditions of SF₆-gas-insulated equipment. This study is a preliminary test of the use of cassiterite (110) for detecting SF₆ and SF₆ decomposition gases, including HF, H₂S, SO₂, SOF₂, SO₂F₂, CF₄, CO, and CO₂. First-principles calculations were adopted to investigate the adsorption mechanism of SF₆ decomposition gases on a cassiterite (110) surface, using adsorption energy, geometrical structure, frontier molecular orbitals, electron density, density of states, potential energy, and work functions. We found that the adsorption of H₂S made a noticeable change in the electronic properties of the (110) surface. The adsorption of SO₂ strongly influenced the charge distribution of the cassiterite (110) surface and made the greatest decrease in the work function of the nine gas molecules tested. Conversely, changes in the cassiterite's electronic properties induced by other gases, especially SF₆, were slight. Therefore, cassiterite could be a promising candidate for highly selective and sensitive sensors to detect H₂S and SO₂ in SF₆ decomposition gases.