A theoretical study on the gas-phase fire suppression mechanism of potassium-based compounds

Potassium salts are widely recognised as highly efficient and clean fire suppressants, yet their reaction mechanisms with free radicals under high-temperature conditions remain to be thoroughly elucidated. In this work, elemental K and its oxidised and hydrogenated derivatives are taken as the research objects. Geometry optimizations are performed on all plausible configurations of KOn, KHn and KOnHm systems, and their thermal stabilities at high temperatures are further investigated. The results indicate that several potassium-based compounds possess favourable thermal stability under high-temperature conditions, suggesting that they may serve as key species in gas-phase fire suppression. On this basis, the free energy barriers and reaction rate constants of reactions between KH, KOH, KO2, KO, KO2H, KO2H2 and core combustion radicals (H, O, OH, HO2) are further calculated. Notably, KO2H and KO2H2, newly identified and verified to be thermally stable at high temperatures in this study, are species not accounted for in conventional mechanisms. They are predicted to participate in the radical consumption process, thereby expanding the range of potassium-based species considered in theoretical flame inhibition mechanisms.