Spray-dried MOF-derived bimetallic oxide/carbon hybrids with superior electron transfer capability for catalyzing ammonium perchlorate decomposition

The thermal decomposition characteristic of ammonium perchlorate (AP) represents a critical factor in determining the performance of solid propellants, which has aroused significant interest on the structure and performance improvement of kinds of catalysts. In this study, bimetallic metal-organic frameworks (MOFs), such as CuCo-BTC (BTC = 1,3,5-Benzenetricarboxylic acid, H 3 BTC), CuNi-BTC, and CoNi-BTC, were synthesized by solvothermal (ST) and spray-drying (SD) methods, and then calcined at 400 °C for 2 h to form metal oxides. The catalysts as well as their catalytic effects for AP decomposition were characterized by FTIR, XRD, SEM, XPS, TG, DSC, TG-IR, EIS, CV, and LSV. It was found that the rapid coordination of metal ions with ligands during spray drying may lead to catalytic structural defects, promoting the exposure of reactive active sites and increasing the catalytic active region. The results showed that the addition of 2 wt% binary transition metal oxides (BTMOs) as catalysts significantly reduced the high-temperature decomposition (HTD) temperature of AP and enhanced its heat release. Of particular significance is the observation that SD-CoNiO x , prepared by spray-drying, reduced the decomposition temperature of AP from 413.26 °C (pure AP) to 306 °C and enhanced the heat release from 256.79 J/g (pure AP) to 1496.82 J/g, while concomitantly reducing the activation energy by 42%. By analysing the gaseous products during the decomposition of AP+SD-CoNiO x and AP+ST-CoNiO x , it was found that SD-CoNiO x could significantly increase the content of high-valent nitrogen oxides during the AP decomposition reaction, which indicates that the BTMOs prepared by spray-drying in the reaction system are more conducive to accelerating the electron transfer in the thermal decomposition process of AP, and can provide a high concentration of reactive oxygen species that oxidize AP to high-valent nitrogen oxide-containing compounds. The present study shows that the structure selectivity of the spray-drying technique influences surfactant molecular arrangement on catalyst surfaces, resulting in their ability to promote higher electron transfer during the catalytic process. Therefore, BTMOs prepared by spray drying method have higher potential for application.