Analysis of the Thermal Decomposition Path of SF 6 on the Surface of Cu and its Oxides

Accurately grasping the decomposition path of SF 6 on the surface of typical metals and metal oxides is the key to reveal the decomposition mechanism of overheating fault. In this paper, the decomposition paths of SF 6 on Cu and its oxides are theoretically analyzed by combining density functional theory and transition state theory. The results show that the participation of Cu surface reduces the energy required for the initial decomposition of SF 6 by about 98.70 kcal/mol compared to that in free space. The decomposition reaction of SF 5 on the Cu surface is energy barrier free, thus SF 5 cannot stably exist in SF 6 over-thermal decomposition system. Further, it was found that when Cu was oxidized at high temperature, reactions between SF 6 and metal surface would be more intense. At this time, the total reaction heat of SF 6 completely decomposed into S was -220.07 kcal/mol, significantly lower than -100.60 kcal/mol on Cu surface. This illustrates the catalytic effect of Cu and its oxides. On the surface of CuO, the interaction of O and F atoms may be the main reason to further reduce the activation energy. This article explained the over-thermal decomposition process of SF 6 from microscopic level, laying a theoretical foundation for further study on the influence of the over-thermal decomposition of SF 6 -metal system.