Hypergolicity improvement by activated carbon-supported catalysts for hydrogen peroxide oxidizer

In recent years, hydrogen peroxide (H2O2) has been attracting attention as an alternative oxidizer to replace the traditional toxic hypergolic oxidizers. However, hypergolic solid fuel (HSF) candidates for H2O2 are few in number and offer limited applications for space propulsions. In this work, various activated carbon (AC)-supported catalysts for a H2O2 hybrid rocket were studied to improve the hypergolicity of HSF, thereby widening the selection range for hypergolic fuels. For this purpose, eleven H2O2 catalyst candidates (Cr, Mn, Fe, Co, Ni, Cu, Ru, Pd, Pt, Pt–Ru, and Pb) were deposited onto AC supports at contents of 20 wt%. The nanostructure and metal particle size distribution of these prepared catalysts were investigated via transmission electron microscope imagery. The oxidation states of the supported catalysts were determined by X-ray diffraction, while the ignition characteristics of the pure catalysts and HSFs with catalyst additives were examined by conducting hypergolic drop tests using a 95 wt% H2O2. The hypergolicity of the prepared catalysts was evaluated by measuring their reaction delay and ignition delay times. Among the studied catalysts, Pt/AC, Ru/AC, and Pt–Ru/AC exhibited the shortest reaction delay time of 0.3 ms. Moreover, the dependences of the reaction delay time on the presence of Na+ ions in Mn/AC and Mn concentration were established. Finally, the ignition delay time of an HSF containing 25 wt% ammonia borane and 75 wt% polyethylene decreased from 20.3 to 9.8 ms after the addition of 1 wt% Pd/AC. These results can provide a variety of additive options for improving hypergolicity of solid fuels with H2O2.