| Carbon encapsulated metal nano-particles (CEMNPs) are types of carbon/ metal composite materials with core/shell structure in nanoscale. The different combination of various metal nanometer materials as core and carbon as shell rewards the composite with many peculiar physical and chemical properties. Therefore, CEMNPs have huge potential applications in many fields, such as new energy and materials, biomedicine, industrial catalysis, and so on. Hence, the preparation, properties and applied basic research of carbon encapsulated metal nano-particles as a new kind of carbon based nanocomposite have become a research hotspot. Hydrothermal method, which is known as a solution-based chemical method, might provide an effective and convenient route to generate nanoscale materials with great advantages such as high efficiency, inexpensive equipment and dispensing with any inert atmosphere protection. The preparation of CEMNPs by hydrothermal method have the features with good dispersion, facile process, low costs, high grade strong controllability, etc.In this study, Cu particles encapsulated in carbonaceous shells (Cu@C) were mildly prepared via a one-pot hydrothermal method using copper nitrate, glucose, sodium citrate and others as raw materials. The obtained products were characterized by X-ray diffraction (XRD), and transmission electron microscopy (TEM), and scanning electron microscope (SEM), and FT-IR spectrum analysis. SEM snd TEM images showed that the products were composed of copper/ carbon micro-sphere or polyhedral with diameters ranges from 1 to 5μm. XRD results showed the core of Cu@C is mainly composed of the polycrystal of fcc-Cu and the shells are amorphous carbons. Some functional groups, such as C=C, OH, and C=O groups, might covalently bond to the carbon frameworks, which has been identified by an IR spectrum. The influences of reaction time and temperature, different carbon sources and the dosage of surfactant on the structure, morphology and chemical composition were also investigated in detail. The main results were summarized as follows:The optimum reaction temperature is 160～180℃; appropriate reaction time could promote the nucleation of copper and growth of the exterior complete carbon shell. It is better to choose the carbohydrates with relatively small molecule as carbon sources, for example, glucose, sucros. We also found that the grain size of crystalline copper was decreased with increasing the molar ratios of sodium citrate to Cu2+ and polyvinylpyrrolidone played an important role for morphology control.Two different hydrothermal processing were conducted for the preparation of (Cu-Ce)@C and the obtained products were characterized by XRD, SEM, etc. Characterization results showed both ways could obtain the core-shell particles. XRD results showed that the metal core was made up of copper and cerium in forms of elemental or oxide, simultaneously. SEM images showed the particles were spheric morphology, while the shape was regular and the particle size was 1～4μm. In addition, the CeO2/Cu@C was also prepared by impregnation method based on the Cu@C. The obtained products were characterized in the same way.The as-made (Cu-Ce)@C and CeO2/Cu@C were applied on NO removal through a micro fix-bed reactor. The results indicated that the removal efficiencies of NO for all samples were more than 30% under the condition of 40℃,1016ppm NO, and lOm·min-1 gas flow. The removal efficiency of CeO2/Cu@C as catalysts was higher than that of (Cu-Ce)@C, up to 70.4% under the same conditions. Increasing the concentration of CO in reaction system led to the decrease of NO removal efficiency. In this study, the preparation method of carbon/metal composite materials is simple and low costs.And, the composite might possess potential applications for NO removal. |
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