Adsorption mechanism and compatibility of environmentally friendly insulating gas CF3I and its main decomposition products with Al and Cu(1 1 1) surfaces

Abstract

Good environmental compatibility and excellent insulation performance make trifluoroiodomethane (CF3I) have the potential to replace SF6 in gas-insulated equipment. The gas–solid compatibility of CF3I, its main decomposed products (I2, C2F6, C3F8, C2F4, HF, CF3H, COF2), and environmental molecule H2O with the Al and Cu(111) surfaces is investigated based on first-principles calculations. The most stable adsorption configurations of Al and Cu(111) surfaces adsorbed by all gas molecules are constructed, and the interaction types between gas molecules and two metal surfaces are determined by adsorption energy (E ad), charge transfer, and charge density difference. The absolute E ad of CF3I and I2 adsorbed on Al(111) surfaces are 4.09 and 3.76 eV, respectively. In contrast, the absolute E ad of other gases adsorbed on Al(111) surfaces do not exceed 0.99 eV, indicating that CF3I and I2 have strong chemical interactions and poor gas–solid compatibility with Al(111) surfaces, while other gases exhibit good gas–solid compatibility with the Al surface. The absolute E ad of I2 (1.15 eV) adsorbed on Cu(111) surface is significantly larger than that of other gases-adsorbed systems (not exceeding 0.99 eV) including CF3I-adsorbed system, proving that the gas–solid compatibility of I2 with Cu(111) surfaces is worse than that of other gases. In addition, the reasons for the different compatibility of CF3I with Al and Cu(111) surfaces are analyzed in depth through the density of states.