Hypergolic ionic liquids (HILs) have emerged as promising self-igniting green space propellants in combination with an oxidizer, replacing toxic hydrazine family rocket fuels. Despite numerous new HILs being reported in the literature, there is no systematic study addressing the key reaction mechanism of such hypergolic ignition. Here, the first comprehensive molecular level understanding of this ignition reaction is revealed, exploring a 1-ethyl-3-methylimidazolium cyanoborohydride-hydrogen peroxide ([EMIM][CBH]-H