Electrolysis of Solvent‐Free Ammonium‐Dinitramide‐Based Liquid Propellant

ABSTRACT

Ammonium dinitramide (ADN)‐based liquid propellants are promising because of their high energy density. Electrical ignition offers a simple means of triggering combustion in such ionic liquids. However, the electrolysis behavior of ADN‐based formulations remains poorly investigated. This study aims to clarify the electrolysis of an equimolar mixture of ADN and hydroxyethylhydrazinium nitrate (HEHN). Herein, chronoamperometry combined with in situ Raman spectroscopy was conducted to analyze the liquid phase under an applied voltage, and in situ high‐resolution time‐of‐flight mass spectrometry (HRTOFMS) was used to characterize the evolved electrolysis gases at the anode and cathode. ADN/HEHN exhibited a higher chronoamperometric current density than neat HEHN, indicating that ADN acts as a charge carrier, thereby enhancing electrical conductivity. In situ Raman spectroscopy revealed a time‐dependent decay of bands assigned to ADN and HEHN, demonstrating that dinitramide and nitrate anions are the principal electroactive species at both electrodes. HRTOFMS revealed that nitrous oxide (N ₂ O) and water (H ₂ O) were the major gaseous products, with large amount of N ₂ O produced at the cathode. Based on these observations and previous study findings, a possible electrolysis reaction mechanism is proposed: at the cathode, the reduction of dinitramide anions (DN ⁻ ), ADN, and nitrate anions leads to the formation of N ₂ O, H ₂ O, and NH ₃ through subsequent reactions, whereas at the anode, the oxidation of DN ⁻ and nitrate anions produces N ₂ O and H ₂ O via follow‐up reactions. These results reveal that ADN/HEHN electrolysis directly produces oxidizing species such as N ₂ O, which, together with fuel species produced by pyrolysis, facilitate ignition.