Synthesis of highly stable FeCo alloy encapsulated in organized carbon from ethylbenzene using H2, CH4, C2H4 generated in situ

Abstract

Abstract A FeCo alloy encapsulated in carbon from ethylbenzene using H2, CH4 and C2H4 generated in situ is presented. The different materials were characterized by X-ray diffraction (XRD), temperature programmed reduction (H2-TPR), thermogravimetric analysis (TG), scanning electron microscopy (SEM-FEG), transmission electron microscopy (TEM), Raman spectroscopy, Vibrating Sample Magnetometer (VSM) and gas chromatography (GC). The XRD and TG results indicate that the formation of a FeCo alloy encapsulated in crystalline carbon is favored at a high temperature. The TPR profile showed that the oxide was completely reduced to FeCo alloy in the temperature range used for the ethylbenzene dehydrogenation reaction (550–700\u202f°C). The images obtained by FEG-SEM and TEM indicate the formation of carbon filaments and that the FeCo alloy favors the growth of structurally organized carbon. The ratio of the D and G bands from the Raman spectra confirm that organized carbon growth using a FeCo alloy is favored at higher temperatures. The hysteresis curves (VSM results) presented higher saturation magnetization for lower synthesis temperatures, confirming that the saturation magnetization is higher for smaller crystallite sizes. The FeCo alloy encapsulated in carbon is resistant to chemical attacks such as acid attacks and an oxidizing atmosphere compared to the FeCo alloy that was not encapsulated with carbon. It was possible to propose a mechanistic route for forming a FeCo alloy encapsulated in carbon from the products identified in the chromatograms and the characterization results. The FeCo alloy is formed from the hydrogen released in situ during ethylbenzene dehydrogenation reaction. Organized carbon growth in a FeCo alloy occurs from the methane and ethylene generated in situ during the toluene and benzene reactions, respectively.