Synthesis And Electrochemical Performances Of FeMoO₄/CNTs Composite Materials As Electrode For Supercapacitor

Now the economic strength and the scientific level of the world are developing,the sources of energy is indispensable to the development of human society.Since twenty-first Century,many researchers have focused their attention on super capacitor that is a new energy storage device.It is because that this energy storage device has relatively high power density,fast charge discharge performance and excellent electrochemical stability.Supercapacitors have very important applications in a series of fields,such as electric vehicles,mobile phones,computers,portable electronic devices,and energy and power generation.Therefore,the new energy storage device has very important application prospects and market demand.The supercapacitor consists of three parts,the electrode material,the electrolyte and the diaphragm.The positive and negative electrode material is the core component of the whole supercapacitor system,because the performance of the electrode material determines the electrochemical performance of the supercapacitor.The factors such as the microstructure,the pore size,the specific surface area and the electron transport capacity of the electrode material have great influence on the electrochemical performance of the material.At present,binary metal oxides are very promising supercapacitor electrode materials.There are very few reports on the application of FeMo04,a binary metal oxide,to supercapacitors.Therefore,this paper mainly focuses on the synthesis methods and conditions,electrical conductivity,electrochemical performance and cycling stability of FeMoO4 electrode materials.We have explored the optimum hydrothermal temperature for the synthesis of this material.In addition,CNTs were composited on the surface of FeMoO4 by chemical vapor deposition.The material is further optimized from the aspects of its topography,specific surface area,and conductivity.The specific research work is as follows:(1)We successfully obtained a FeMoO4 nanorod array using a simple hydrothermal method on a foamed nickel substrate.The effects of different hydrothermal synthesis temperatures on the microscopic morphology and electrochemical performance of the material were investigated.The materials were characterized by means of XRD,XPS,SEM and TEM.And electrochemical testing methods such as CV,GCD and EIS are used for electrochemical testing of materials.The results show that either from the sample morphology or from the electrochemical performance of the sample,the hydrothermal temperature of 180 °C is the best synthesis condition for the synthesis of FeMoO4 nanorod electrode materials.Electrochemical performance tests showed that the area specific capacitance of the FeMoO4 nanorod electrode synthesized at a hydrothermal temperature of 180 °C at a current density of 3 mA/cm2 reached 1.34 F/cm2.Compared with FeMoO4 electrode synthesized under other conditions,its area specific capacitance is the highest,and there is still more excellent electrical conductivity.The specific capacitance remains at 85.1%even at current densities up to 10 mA/cm2.(2)FeM004/VCNTs composites were successfully synthesized.We used C2H2 as a carbon source and used chemical vapor deposition to synthesize CNTs on the surface of FeMoO4 nanorods synthesized under the optimal conditions in(1).CNTs have been considered as ideal supercapacitor electrode materials due to their excellent electrical conductivity,very high aspect ratio,high mechanical strength,and excellent chemical stability.Therefore,we use CNTs to complex FeMoO4 nanorods.The composition and morphology of FeMoO4/CNTs composites were characterized by means of Raman,XPS,SEM,TEM,electrochemical CV,GCD,and EIS,and the electrochemical properties were analyzed in detail.We have conducted a series of studies on the effects of different deposition temperatures on vapor-deposited CNTs composite FeMoO4 nanorod electrode materials.The results showed that the CNTs composite FeMoO4 nanorods(FeMoO4/CNTs-360)synthesized at a temperature of360°C exhibited the most excellent electrochemical performance.Using FeMoO4/CNTs-360 as the cathode material in a three-electrode system,the specific capacitance is as high as 3.332 F/cm2 at a current density of 3 wA/cm2.This result is much higher than the specific capacitance of the pure FeMoO4 electrode material synthesized in(1).We also assembled FeMoO4/CNTs-360 as cathode material and activated carbon(AC,anode material)into asymmetric supercapacitors.The device still maintains 60%of initial capacitance after 1000 charge/discharge cycles.