Carbon Nanotube-Embedded Metal Carbonyl Compound Nanocomposites: Efficient Catalysts for Thermal Decomposition of Ammonium Perchlorate

Abstract

Adding burning-rate catalysts (BRCs) is highly effective for enhancing ammonium perchlorate (AP) thermal decomposition. To mitigate BRCs’ agglomeration and enhance their catalytic activity for AP pyrolysis, five metal carbonyl compounds (Mo(CO)6, Cr(CO)6, W(CO)6, Fe2(CO)9, Mn2(CO)10) were refined into oxidized carbon nanotube (CNTs) cavities, respectively, by ultrasonication. The structures of the as-prepared nanocomposites were examined with TEM, SEM, XPS, Raman, etc., confirming the successful filling of the carbonyl compounds. Electrochemical studies revealed that the Mo(CO)6@CNTs(N1) exhibited an enhanced electron transfer rate and superior electrocatalytic performance compared to CNTs(N1). Their catalytic performance evaluated by DSC showed that 5 wt.% Mo(CO)6@CNTs(N1) exhibits the best catalytic effect, increasing the heat release of AP by 2904.63 J·g-1, advancing its peak temperature by 80.6 oC, and decreasing its activation energy by 100.45 KJ·mol-1. The degradation mechanism of AP catalyzed by Mo(CO)6@CNTs(N1) was probed through TG-FTIR-MS, in-situ solid FTIR, and theoretical calculations. The investigations suggested that the promoter in AP generates carbon nanotubes-confined MoO3 nanoparticles featuring numerous Lewis and Brønsted acidic sites, which not only improves NH3 adsorption and activation but also enhances electron transfer and accelerates O2 conversion to O2-, thereby facilitating AP pyrolysis. Finally, a plausible catalytic mechanism for AP decomposition is postulated.

Keywords: metal carbonyl compound, Carbon nanotubes, Embedding, Combustion catalytic performance, Decomposition mechanism of AP.