Copper–Cobalt Oxide Nanoparticles with Tailored Cobalt Oxidation State and Lattice Oxygen Vacancy for Low-Temperature Ignition of Ammonium Dinitramide Monopropellants

Ammonium dinitramide (ADN) ionic liquid monopropellants are recognized as suitable green substitutes for hydrazine and have attracted considerable research interest. However, the cold-start capability of a monopropellant is a critical requirement in propulsion applications, and ADN monopropellants are not cold-start capable. In this study, we introduce non-noble metal oxide-based Cu-incorporated Co 3 O 4 (Cu–Co 3 O 4 ) spinel nanoparticles for the low-temperature catalytic ignition of an ADN-based liquid monopropellant variant, LMP 103X. The Cu incorporation reduces the particle size and enhances the surface properties of Co 3 O 4 . The catalytic activity of Cu–Co 3 O 4 for the decomposition of LMP 103X monopropellant was investigated by using a simultaneous thermal analyzer. The Cu–Co 3 O 4 nanoparticles enhanced the reaction rate and showed better catalytic performance by lowering the decomposition temperature from 178 to 132 °C, with sudden decomposition of the entire propellant sample. More grain boundaries observed in Cu–Co 3 O 4 possibly enhanced the adsorption and transport of reactant species across the catalyst. The synergistic effect of the high Co 3+ /Co 2+ ratio, oxygen vacancies, pore volume, grain boundaries, and segregation of CuO enhanced the catalytic activity of the Cu-incorporated Co 3 O 4 . The efficiency of the catalyst is analyzed by the oxidation states of the transition metals, the abundance of active sites, and oxygen vacancies appearing on their surfaces.