Synthesis Of Bi₂O₃ Microspheres And Ferrocene Modified Carbon Nanotubes And Their Application In Supercapacitors

Supercapacitors combine the common advantages of chemical batteries and traditional capacitors.They not only have the charging and discharging power of traditional capacitors,but also possess the ability to store a large amount of charges.They are a new type of energy storage device with non-pollution and excellent performance.It has been widely studied because of its high power density,long cycle life,and fast charge and discharge speed,which provides a good opportunity for the development of more advanced hybrid energy storage systems.In each component of the supercapacitor,the electrode material plays an indispensable role,and its type and performance greatly determine the overall performance and application of the device.Therefore,the key to improving energy density is to improve the supercapacitance performance of electrode materials.Based on this idea,?-Bi₂O₃ hollow microspheres self-assembled from nanosheets and ferrocene-based functionalized carbon nanotubes(CNT-Fc)were prepared and used as electrode materials in the field of supercapacitors,respectively.The main research contents are as follow:(1)Through solvothermal method and subsequent high-temperature heating,the micro morphology of ?-Bi₂O₃ hollow spheres electrode material was obtained.The effects of the proportion of glycol/ethanol in solvothermal and different heating temperature on the morphology and phase composition of the sample were investigated.The diameter of the sphere is about 2 um,the width of the nano sheet is about 15-17(±2)nm,and the gap between the nano sheets is about 41-167(±10)nm,the hollow micro sphere structure composed of nano flakes can make full use of the material,thus improving the performance of the super capacitor;in addition,?-Bi₂O₃ obtained by high temperature heating has good crystallinity and is very stable at room temperature,providing more channels for ion storage and transfer,so that the electrode has excellent rate performance.The electrochemical test results show that the maximum specific capacitance of ?-Bi₂O₃ micro sphere is 1380.2 F g^-1 at the current density of 1 A g^-1,which is the largest specific capacitance obtained so far compared with the reported electrode material bismuth oxide.(2)Due to its good conductivity and chemical stability,carbon nanotubes are considered as one of the ideal electrode materials for high current fast charge discharge supercapacitors.However,due to the hydrophobicity of carbon nanotubes,the specific capacity of pure carbon nanotubes needs to be improved.Reasonable oxidation treatment can modify its surface structure and functionalize its surface,which is an effective strategy to further improve its energy storage performance.Firstly,CNT-COOH-n(n=1,2,3)was synthesized by chemical oxidation,and then-CO-Fc was introduced into MWCNTs by two steps instead of hair,so CNT-Fc-n(n=1,2,3)electrode materials were successfully prepared.CNT-Fc-3 prepared by CNT-COOH with oxidation time of 8 h has the best electrochemical performance.The electrochemical test results show that the specific capacitance of CNT-Fc-3 electrode material is 56.2 F g^-1 when the current density is 0.4 A g^-1 in the electrolyte of 1 M Na₂SO₄.Under the same conditions,the specific capacitance of CNT-Fc-3 electrode material is 2.1 times higher than that of raw MWCNTs particles,and it is 1 A g^-1 After 5000 cycles at the current density of,96% of the initial specific capacitance can still be retained,which shows that the surface reactivity and capacitance can be greatly improved by ferrocenyl bonding.