Unearthing hidden hypergolic potential of energetic complexes with hydrogen peroxide

The development of hypergolic materials has aroused great interest since their significant application in bipropellant systems. In this work, five energetic complexes (1–5) were developed to demonstrate hypergolic performance with the green oxidizer hydrogen peroxide. The compounds were comprehensively characterized. The decomposition temperatures of these compounds were in the range from 228.8 to 295.5 °C. The highest thermal stability was observed in compound 5. The density of these compounds were in the range from 1.389 to 1.502 g∙cm⁻³ which was higher than most of the known hypergolic materials. Furthermore, the hypergolic performance of these materials were evaluated with 90% H₂O₂ by an “oxidizer-to-fuel” standard droplet test. For the examined hypergolic combinations, the shortest ignition delay time was only 3 ms which was observed in compound 2. This ultra-short ignition delay time was shorter than that of most hypergolic combinations and attributed to synergy between different components in the energetic complexes. The copper ion metal center was the key promoting factor affecting hypergolic performance of the target compounds. The organic ligand acted as an energetic fuel while the NO₃⁻ counter ions further improved the hypergolic performance. Integrating these components into one complex and demonstrating their hypergolic performance with hydrogen peroxide as the oxidizer was successfully achieved. The hypergolic phenomenon observed in this work between energetic complexes and hydrogen peroxide may lead to a new approach for the development of green hybrid propulsion systems.