The Synthesis Of Fe3_O4/C Composite Materials And The Study Of Their Properties

As important transition metal oxides, iron oxides (Fe3O4) have been widely researched in energy and environmental fields due to their unique physical and chemical properties. And they are regarded as one of very promising electrode materials of ithium ion battery and catalyst carrier. But pure Fe3O4 as anode materials of lithium ion battery have the shortcomings of low discharge capacity and poor cycle performance, which greatly hindered its practical application. This paper pay attention to the synthesis of of Fe3O4/C compounds with different morphologies synthesis and performance research for lithium ion battery, and extending to the field of photocatalytic application. In this paper, the research content includes the following three aspects:1. Carbon-coated Fe3O4 microspheres with a porous multideck-cage structure for highly reversible lithium storageIn this chapter, we have rationally developed a simple H3PO4 etching method for the preparation of porous multideck-cage a-Fe2O3 microspheres composed of irregularly arranged plate-like subunits. Firstly, hierarchical Fes(Po4)4(OH)3·2H2O microspheres are synthesized by a facile one-pot hydrothermal reaction in the presence of sodium citrate. Secondly, the as-prepared Fes(PO4)4(OH)3-2H2O microspheres are converted into FePO4/Fe2O3 composite microspheres by a two-step thermal transfoamtion process in NH3 at 600℃ for 2 h, and then in air at 700℃ for 2 h. The final Fe2O3-PMCMs are obtained form the FePO4/Fe2O3 composite microspheres via a H3PO4 etching strategy in ethylene glycol (EG) at 35℃ for 1 h. To further improve the electrochemical performance, the as-obtained Fe2O3-PMCMs are coated with a thin carbon layer and annealed in N2 at 500℃ for 4 h, which further improves the electrical conductivity and structural stability. As a result, the as-prepared Fe3O4@C-PMCMs exhibit greatly enhanced Li+storage properties as an anode material for LIBs, with a reversible capacity of as high as-1100 mA h g-1, and showing enhanced structural stabilities even after 50 charge-discharge cycles, which is possibly due to the structural flexibility originated from the unique structure of porous, multideck-cage structured microspheres and the production of carbon layer.2. One-Pot Magnetic Field Induced Formation of Fe3O4/C Composite Microrods with Enhanced Lithium Storage CapabilityIn this work, we have developed a novel magnetic field-induced solvothermal method to synthesize Fe3O4/C composite microrods. In the synthesis, glucose not only serves as the carbon source, but also plays a critical role in gluing Fe3O4 nanoparticles to form Fe3O4/C microrods in the presence of an external magnetic field. It is also found that the amount of EDA in the reaction system has a significant effect on the structure of products formed. The as-prepared Fe3O4/C composite microrods exhibit significantly enhanced electrochemical lithium storage properties with a high reversible capacity of～650 mA h g-1 retained after 100 cycles. The present results again suggest that structural design of electrodes will have important implications on the fabrication of high-performance electrode materials for lithium-ion batteries. It is worth noting that this paper provides a new idea for synthesis of 1D magnetic micro/nano composite materials.3. Direct coating ZnO nanocrystals onto 1D Fe3O4/C composite microrods as highly efficient and reusable photocatalysts for water treatmentIn this section, we demonstrated a facile two-step method to directly coat a ZnO nanocrystal layer on the surface of one-dimensional (1D) Fe3O4/C composite microrods to form Fe3O4/C@ZnO core-shell microrods. Firstly, 1D Fe3O4C composite microrods were successfully synthesized by one-pot magnetic field-induced solvothermal reaction according to our previous work./Sencondly, a uniform ZnO nanocrystal layer was facilely coated onto the 1D Fe3O4/C composite microrods via a modified hydrothermal process at a low temperature (60℃). Importantly, the size of ZnO nanocrystals and the thickeness of coating layer can be easily tuned by varying the concentration of Zn(Ac)2·2H2O in the solution. Further investigation has revealed that the as-prepared core-shell microrods exhibited enhanced photocatalytic activity for the decolorization of photosensitized dyes (Congo red) under visible-light illumination. Moreover, these magnetically separable photocatalysts can be readily recycled by a magnet with virtually no loss in catalytic efficiency. We believe this facile synthesis strategy provides a general and efficient way to synthesize other 1D magnetic nanocomposites for different functional applications.