Activation And Preparation Of Nitrogen-doped Carbon Materials And Its Electrochemical Properties

As the energy crisis continues to intensify,the research on clean energy is also deepening,at present,it is urgent to research and develop new energy storage devices in the scientific work.Duo to the power density,service life and temperature range,supercapacitor are the outstanding energy storage devices,its research and development is increasingly perfect and has a bright application prospect.However,in practical application,the market demand for super-capacitor is increasing,so the research process should be accelerated.Electrode materials have a direct and significant impact on the performance of energy storage devices,so the development of high-performance electrode materials is very important for the research and development of supercapacitors.Because of its advantages of high specific surface area and strong electrical conductivity and chemical stability,carbon materials can provide more ion transport and storage sites,ultra-high power density and outstanding cyclic stability when used as electrode materials.The surface properties of electrode materials and micro pore structure has important influence on the performance of super capacitor,chemical doping and modification ways under different impurity atoms into the carbon skeleton,can reduce material internal resistance,improve the conductivity and surface activity,adjust the pore structure,improve the electrochemical characteristics of carbon materials,won the outstanding performance of electrode materials.Therefore,the main research content of this paper is as follows:（1）In this paper,graphene oxide（GO）,cobalt nitrate（Co（NO₃）₂）and melamine were used to prepared nitrogen-doped graphene/carbon nanotubes/amorphous carbon（NC）composites which used the catalytic action of cobalt on pyrolytic carbon source at high temperature.Then tested NC electrochemical properties.The effects of metal and melamine addition levels on the structure and properties of carbon matrix composites were investigated.It was found that when the addition levels were 0.02 mmol and 0.3 g,respectively,the prepared materials had large specific surface area(380.5 m²g^-1)and nitrogen content（N6.29 wt.%）.The electrochemical performance of the three electrode system is excellent.When the current density is 0.5 A g^-1,the material specific capaci-tance is 137.1 F g^-1,when the current density is 5 A g^-1,the specific capacitance is 113.5 F g^-1,and the retention rate is 88.5%.After 5000 cycles,the capacity retention rate of the material is 104%,showing excellent rate performance and good cycle stability.It’s attributed to the fact that the three-dimensional structure can accelerate ion transfer during charge and discharge process and nitrogen doping can improve material wettability and contribute part of pseudocapacitance,providing theoretical reference for the preparation of electrode materials for supercapacitors.（2）In order to improve the pore structure and surface chemical properties of sample NC-M3 and improve its electrochemical activity,different chemical reagents and methods such as HNO₃,KOH and H₂O₂were used to activate the sample NC-M3-0.02,and the effects of different activators and activation methods on the pore structure and surface properties of the material were investigated.As for the sample NC-M3-HNO₃,the specific capacitance is 149.8F g^-1when the current density is 0.5 A g^-1,and 121 F g^-1when the current density is 5 A g^-1.The specific surface area and oxygen-containing functions of the sample NC-M3-KOH increased,the pore size distribution was improved,and the contribution rate of pseudocapacitance to electrolyte ion transfer rate was increased.The specific capacitance was 168 F g^-1when the current density was 0.5 A g^-1,and 145.5 F g^-1when the current density was 5 A g^-1.After 5000cycles,the capacity retention rate is 115%,which has good circulation performance.As for the sample NC-M3-H₂O₂,when the current density is 0.5 A g^-1,the specific capacitance is 156.2 F g^-1,and when the current density is 5 A g^-1,the specific capacitance is 121 F g^-1.Therefore,the activated carbon material shows excellent electrochemical performance and has a strong potential of capacitor electrode material.