Effect of micro-H₂O and micro-O₂ on the decomposition characteristics of insulating medium C₃F₇CN gas using molecular...

In recent years, heptafluoroisobutyronitrile (C₃F₇CN) has been proved to be a potential eco-friendly insulating medium to replace sulfur hexafluoride (SF₆, the strong greenhouse gas). In this paper, the effect of micro-H₂O and micro-O₂ on the decomposition of C₃F₇CN was investigated based on the reactive force field molecular dynamics (ReaxFF-MD) and transition state theory (TST). It was found that H₂O obviously promoted the decomposition of C₃F₇CN, and new products HF, COF₂, CO, and NO were generated. The influence of O₂ on the C₃F₇CN dissociation was weaker than that of H₂O, and O₂ slightly promoted the C₃F₇CN decomposition only when 50 O₂ molecules were added. The simultaneous presence of H₂O and O₂ promoted the decomposition of C₃F₇CN, the promotion of which was closed to H₂O existing alone. The calculation results showed that the energy barriers of the two reactions forming COF₂ were 31.38 kcal/mol and 23.85 kcal/mol, respectively, which indicated that the reactions were difficult to proceed spontaneously. The energy barrier of F + H₂O → HF + OH was relatively lower than that of COF₂. These values corresponded well to the ReaxFF simulation results. This study provides theoretical support for the effect of H₂O and O₂ on the decomposition of C₃F₇CN.