Hydrothermal Synthesis Of Fe₂O₃ Nanocomposite And Their Electrochemical Properties

As a new type of energy storage component,supercapacitor has been the research focus in the area of clean energy because of its advantage such as,low equivalent series resistance,fast power delivery,high-power density,high cycle efficiency and long life cycle.Iron oxide,as a kind of typical transition metal oxide semiconductor material,has good faradaic pseudocapacitance characteristics.Compared with the conventional supercapacitors materials?Such as,graphene,carbon nanotube,carbon-based material etc,Ru O₂,Co₃O_<sub>2,transition metal oxides etc.materials?,the iron oxide was abundant,inexpensive,environmentally friendly.However,the electronic conductivity,cycle performance and specific capacity of pure Fe₂O₃ were poor.To the above problems,various morphologies of Fe₂O₃ nanoparticles have been synthesized by a facile hydrothermal in this work.Then we prepared nanocomposites based on different morphologies of Fe₂O₃ with graphene and carbon nanotubes to research the supercapacitor characteristics systematically.The main works were listed as follows.Firstly,different morphologies of Fe₂O₃ nanorods were synthesized by a facile hydrothermal method,and its morphology and electrochemical performance were characterized.The effect of Phosphate ions on morphology were investigated.Phosphate ions were speculated capping to the sidewalls of Fe₂O₃ nanocyrstals,and resulted in the anisotropic growth of hematite crystals along their [006] zone axis.The Fe₂O₃ nanorods with various aspect ratio resulting in the higher specific surface area and larger electrode-electrolyte contact area and thus improved the diffusion rate of ions within the bulk of the prepared materials.So the electrochemical performance showed significant difference.The test showed that the samples with the smallest aspect ratio possessed the superior specific capacitance and stability.Secondly,various morphologies of Fe₂O₃/MWCNTs composites were prepared by hydrothermal method.The morphology of the Fe₂O₃/MWCNTs composites was characterized and the electrochemical properties were tested.Results demonstrated that the small Fe₂O₃ nanoparticles growed on the surfaces of CNTs,but the large Fe₂O₃ nanoparticles could not.The much improved electrochemical performances of?5 nm,30 nm,ring,hollow,flake?Fe₂O₃/MWCNTs could be attributed to the good conductivity of CNTs as well as the anchored Fe₂O₃ particles on the CNTs,which was helpful to increase the specific area of the composites and thus facilitated rapid electronic transport in electrode reactions.The maximum specific capacitance of hollow Fe₂O₃/MWCNTs composites reached up to 183 F/g at a discharge current density of 1 A/g,and exhibited excellent cyclic stability,which displayed good supercapacitor characteristics.Finally,various morphologies of Fe₂O₃/graphene?Fe₂O₃/r GO?composites were synthesized by hydrothermal method.The morphology of the Fe₂O₃/rGO composites was characterized and the electrochemical properties were tested.Structural and morphological studies showed that the as-prepared Fe₂O₃/r GO nanocomposites were actually composed of Fe₂O₃ nanoparticles loaded in rGO nanosheets to form two-dimensional nanostructure.The unique 2D nanostructure of Fe₂O₃/r GO nanocomposites was conducive to not only shorten the transport distance of the ions but also further improved the utilization of the active materials.The Fe₂O₃?5 nm,30 nm,ring,hollow,flake?coated on the surfaces of rGO nanosheets,which could facilitate fast electron transfer between the active materials and electrolyte as well as improve the electrical conductivity.The maximum specific capacitance of Fe₂O₃/r GO?partical size with 30 nm?composites was 135 F/g at a discharge current density of 1 A/g.Then it only showed a slight decrease and the maximum 80% capacitance could be retained after 1000 cycles,which indicated that the Fe₂O₃/graphene composites had better supercapacitor properties than pure iron oxide and Fe₂O₃/MWCNTs.