Effects of closo -icosahedral periodoborane salts on hypergolic reactions of 70% H₂O₂ with energetic ionic liquids

A number of energetic ionic liquids (EILs) have been reported as promising hydrazine-replacement fuels for hypergolic rocket propulsion. However, most of these EILs were ignited using corrosive and hazardous concentrated fuming nitric acid. Very significant efforts were recently made to utilize "rocket grade" highly concentrated H₂O₂ (>90%) as a "green" alternative to fuming nitric acid and N₂O₄ oxidizers. Although "rocket grade" H₂O₂ is more challenging to use and less safe for storage than commercially available H₂O₂ (70%), the latter is not considered as a viable oxidizer for hypergolic propulsion. In this work, we focused on the development of novel iodine-rich promoters, capable of initiating hypergolic ignition reactions between a typical EIL fuel-3-ethyl-1-methyl-1H-imidazol-3-ium cyanotrihydroborate-and H₂O₂. Among the prepared and evaluated promoters, the top performing [FcCH₂NEtMe₂ ⁺]₂[B₁₂I₁₂ ^2-] compound 5 showed ignition delay times of 45 ms in the reaction of the tested EIL with H₂O₂ (70%) and 17 ms with H₂O₂ (95%). We believe that these findings provide a platform for the development and utilization of commercially available H₂O₂ as a potential "green" oxidizer for rocket propulsion.