Dual Role of Dopant CO ₂ /O ₂ in C ₄ F ₇ N Insulating Gas Based on Density Functional Theory Calculation

Perfluoroisobutyronitrile (C₄F₇N) has emerged as a sustainable alternative to SF₆ in gas-insulated equipment (GIE). However, its high boiling point of -4.7 °C and fast thermal decomposition rate under extreme conditions impede its large-scale practical application. These limitations can be mitigated by doping with CO₂ and a low concentration of O₂. Herein, we establish different mixtures of C₄F₇N and CO₂ to identify the optimal mixing ratio. Electronic structure analyses reveal the dipole-induced multiinteractions with blending of CO₂ with C₄F₇N, optimizing liquefaction behavior with the best ratio of 1/9. Simultaneously, to understand the mechanism by which introducing a low concentration of O₂ inhibits decomposition-derived carbon deposition at high temperatures, we analyze the effects of the different O₂ concentrations in the decomposition, based on the mixture model of C₄F₇N-CO₂ with the ratio of 1/9. This work establishes the first atomic-level framework connecting the electronic interactions of C₄F₇N and dopants CO₂/O₂ to macroscopic insulation performance, providing high efficiency for designing or modifying eco-friendly insulating gases with structural stability and dielectric properties.