Preparation Of Nitrogen-doped Titanium Dioxide Microspheres/Polypyrrole Composite Electrode Material And Their Electrochemical Performances

The dual attention of energy and the environment has promoted the exploration of a new generation of energy storage and conversion technologies.As a new type of energy storage device,supercapacitor combines the characteristics of high energy density of chemical batteries and high power density of traditional capacitors.In addition,it also has the advantages of long cycle life,environmental protection,wide operating temperature range,and low maintenance cost.Which have made it becomes an important member in the field of new energy storage.Nano-TiO₂has a large specific surface area,good electron transport performance,and excellent stability.However,the TiO₂has a wide band gap,low specific capacity,and poor conductivity,which make it difficult to fully exert its performance in the field of electrochemical energy storage.Therefore,modified TiO₂is of great significance to improve its electrochemical performance.In this paper,Based on the preparation of anatase phase TiO₂by hydrothermal method,the electrochemical properties of anatase phase TiO₂electrode material were studied,and the nitrogen-doped titanium dioxide/polypyrrole(N-TiO₂@PPy)electrode materials were prepared by doping and electrochemical polymerization,which greatly improved the electrochemical performance of TiO₂and also improved the stability of polypyrrole(PPy).The specific research works of the paper are as follows:(1)Anatase TiO₂multistage microspheres were synthesized by one-step hydrothermal method.And the electrochemical performance of TiO₂were studied in a three-electrode system.Anatase TiO₂has a high area specific capacity(2.26 mF/cm²)and long-term cycle stability(capacitance retention rate is more than 90%after 10,000 cycles).The TiO₂is of little value in the practical application of supercapacitors,but it lays the foundation for the later modification of anatase titanium dioxide.(2)Taking urea as the nitrogen source,the anatase phase TiO₂is doped and modified by the hydrothermal synthesis method.The influence of urea content on the electrochemical performance of TiO₂was explored.The results show that the specific capacitance of TiO₂reaches the optimal value of 11.88 mF/cm²when the amount of urea added is 12g,which is more than five times that of the undoped TiO₂.In addition,nitrogen doping has almost no effect on the cycle stability of titanium dioxide.All electrode materials with different amounts of urea can maintain a capacitance above 90%of the initial value after 10,000 cycles.(3)PPy with different deposition times was prepared by electropolymerization.The electrochemical performance test shows that the performance of PPy deposited for two minutes was the best.Then the N-TiO₂@PPy composite electrode was prepared by depositing PPy on N-TiO₂.The composite electrode combines the advantages of titanium dioxide and polypyrrole to obtain high-performance electrode materials.When the current density is 2m A/cm²,the area specific capacitance of N-TiO₂@PPy reaches at 387.24 mF/cm².After 1000charge and discharge tests,the capacitance value only drops by 8.83%.Take N-TiO₂@PPy as the positive electrode and activated carbon as the negative electrode,the ASSC supercapacitor of N-TiO₂@PPy//AC can work under the voltage window of 0-1.6 V,and the maximum energy density and maximum power density can reach 1.0944 mWh·cm^-3and 75.74 mW·cm^-3,respectively.