Preparation And Applications Of Carbon Encapsulated Metal Nanoparticles

Recent years, carbon encapsulated metal nanoparticles (M@C) have received considerable attention because of their unique core/shell microstructure and physical & chemical properties as well as their potential applications in many high-tech fields, such as biomedical engineering, catalysis, energy sources, etc.Carbon encapsulated metal nanoparticles have been successfully synthesized by pyrolyzing starch/iron composite in flowing hydrogen, in which starch is used as both carbon precursor and stabilizer for metal nanoclusters. The as-obtained carbon encapsulated metal nanoparticles have been characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectroscopy, thermogravimetry (TG) and vibrating sample magnetometer (VSM). The results reveal that the M@C, with diameters in a narrow range, exhibit well-constructed metal core/graphitic shells structure and well thermostability. Besides, the M@C is in a superparamagnetic state at room temperature. Meanwhile, the synthesis process of Fe@C has been investigated and the effect of technical conditions on the formation of Fe@C has been discussed, including starch/iron ratio, heating rate, reaction temperature and time. The mechanism involved in the growth process of carbon encapsulated metal nanoparticles is also discussed briefly. All the results imply that starch is one of the ideal carbon precursors for preparing carbon encapsulated metal nanoparticles.The possibility of as-prepared Fe@C as magnetically separable catalyst support has been investigated. Fe@C supported Ru, Au and Ag catalysts (catalyst/Fe@C) have been prepared through impregnation and polyol process. And the structure of catalyst/Fe@C has been investigated by TEM and XRD. The oxidation of benzyl alcohol to benzaldehyde has been employed as a probe reaction to test the activity and selectivity of the Ru/Fe@C. The results demonstrate that carbon encapsulated iron nanoparticle is one of the ideal magnetically separable catalyst supports.Furthermore, hollow carbon nanocapsules (HCNCs) with diameters in a narrow range have been successfully prepared from Fe@C via acid treatment. The adsorption capacity of HCNCs for thiophene in model oil is much higher than the commercial activated carbon under the same conditions, implying that the HCNCs are of potential as adsorbent in ultra-deep removal of sulfur-containing compounds from fuel oils.