Tailoring the Catalytic Activity of Fe3O4 Nanoparticles for KNO3 Decomposition via Surface Functionalization

Abstract

This study investigates the synthesis, characterization, and catalytic activity of functionalized iron oxide nanoparticles for the thermal decomposition of potassium nitrate (KNO₃). The iron oxide nanoparticles (Fe₃O₄ NP_s) were synthesized using a co-precipitation method and then functionalized with 11-Bromoundecanoic (Fe₃O₄@Br) and 11-Aminoundecanoic acids (Fe₃O₄@NH₂) by chemical route. The functionalized nanoparticles were characterized using Transmission electron microscopy (TEM), Thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), and vibrating sample magnetometry (VSM). The characterization results revealed that the nanoparticles have a uniform size of approximately 8.3 nm, exhibit superparamagnetic behavior, and are successfully functionalized. To compare short and long-chain ligands, we included our previously reported quaternary (Fe₃O₄@NR₄⁺) and tertiary (Fe₃O₄@NR₃) amine-functionalized magnetic catalysts in the catalytic studies. Among the different functionalized nanoparticles, Fe₃O₄@NR₃ exhibited the most pronounced catalytic activity, significantly reducing the decomposition temperature (DT) of KNO₃ to 683.2 °C compared to the other nanoparticles. This enhanced catalytic activity is attributed to the specific interaction between the Fe₃O₄@NR₃ surface and KNO₃ molecules. The activation energies (E_a) for the thermal decomposition of KNO₃ were calculated using the ASTM e628 method, confirming the decrease in activation energy for the Fe₃O₄@NH₂ + KNO₃ mixture compared to pure KNO₃. These findings demonstrate the potential of tailored surface functionalization to improve the catalytic performance of Fe₃O₄ nanoparticles for KNO₃ decomposition, which has potential applications in various fields such as propellants, explosives, and pyrotechnics.