The Preparation And Supercapacitive Properties Of Fe₂O₃/Reduced Graphene Oxide Composite

Because of their diverse valence and high specific capacity,transition metal oxides such as MnO₂,NiO,Co₃O₄,Fe₂O₃,SnO₂,TiO₂,ZnO and so on,show a great potential for supercapacitor electrode material.Among them,Fe₂O₃ has been widely studied as a supercapacitor electrode material as a result of changing oxidation states,abundant resources,low cost,nontoxic and environment-friendly.Due to poor conductivity,Fe₂O₃ owns undesirable rate capability and poor cycle stability,thereby limiting its use as a supercapacitor electrode material.The most common and effective solution is to compound the carbon material with better conductivity to prepare a multicomponent material with good conductivity,special morphology and large specific surface area.Based on the above two points,this paper has made a synergistic effect between the graphene and Fe₂O₃ composite materials,so as to find the modification scheme of high specific capacity electrode material.Meanwhile,we focus on the use of cyclic voltammetry,galvanostatic charge-discharge,AC impedance,Raman,scanning electron microscopy and other techniques to clarify the electrode reaction process and mechanism and to explore the reasons of high capacity and the attenuation of specific capacity.The main contents and results are as follows:（1）The Graphene Oxide（GO）and FeCl3·6H2O were reduced by NaBH4,and then γ-Fe₂O₃/reduced Graphene Oxide（rGO）composites with good conductivity were obtained by calcination at low temperature.The effects of different calcination times and temperatures on the capacitance performance were discussed in detail.Through the analysis of impedance and conductivity,the reasons for improving the conductivity of γ-Fe₂O₃/rGO composites and the influence on the performance of supercapacitors are discussed.（2）The hexagonal α-Fe₂O₃/rGO composites were prepared by a one-step solvothermal method.The effect of precursor ratio on the electrochemical properties of the composites were studied.It was found that the materials with 60 wt% Fe₂O₃ had large capacitance,good magnification and cycle stability.On the one hand,the improvement of the electrochemical properties of the composites is due to the improvement of the conductivity of the composites.On the other hand,the unique lamellar structure of the composites favors the full contact of the electrolyte with the active material.（3）Here we report an effective approach to fabricate a porous and high specific surface area composite as an efficient supercapacitor electrode material,in which the mulberry-shaped α-Fe₂O₃ nanoparticles are coated by wrinkled graphene sheets.The influence of different hydrothermal times and temperatures on the supercapacitive performance of these prepared composites was discussed in detail.It was found that the material had a relatively wide pore size distribution and a large graphene sheet defect when prepared at the appropriate hydrothermal temperature and reaction time.This multi-stage pore structures facilitate the diffusion of electrolyte ions and enhance its specific capacity,so that the material has a better capacitance performance.