The Defect Engineering Of P-nitroaniline Derived Porous Carbon Materials And Their Electrochemical Properties

As an important energy storage device,supercapacitors have irreplaceable advantages in high power density,long cycle life and fast charging and discharging.The charge transport and storage majorly occur in the electrode materials during the energy storage process,which represent the most important factor to determine the performance of supercapacitors.Porous carbon materials are considered as an important electrode material because of their ideal specific surface area,pore structure,wettability,electrical conductivity and stable electrochemical properties.The catalytic and energy storage activities of the electrode can be greatly improved by engineering the defects of carbon materials and introducing specific doped atoms.In this paper,based on p-nitroaniline derived porous carbon,a series of doped porous carbon materials were synthesized by different methods.By optimizing the pore structure and increasing the active energy storage/catalytic sites,the specific capacitance of the electrode was improved.At the same time,supercapacitors with different electrolyte systems are designed.The pseudo-capacitance provided by electrolyte and the capacitance contribution of the material itself are used to jointly improve the energy storage property of the electrode.The research contents are as follows:（1）P-nitroaniline was adopted as the reactant to generate porous carbon precursor,taking advantage of the heat release and gas volatilization in the high-temperature condensation-carbonization process.Then,porous carbon materials（PCs）with good conductivity,large specific surface area and rich N content were formed through pre-carbonization and activation.At the same time,p-nitroaniline was converted into carbon quantum dots（CDs）with high nitrogen content through simple hydrothermal reaction.Finally,a high-quality CD-PCs composite material with well-defined contact interface was formed with ultrasonic assistance.Using the pseudocapacitive active site provided by the highly defective structure of CDs,the optimized composite material（PC-CDs-1.5%）could effectively improve the performance in acidic electrolyte.KI was used as a pseudo-capacitive activity additive in the electrolyte,and CDs could be used as a catalytic activity center to improve the redox process of I^-/I₃^-pairs on the electrode surface,providing sufficient active sites for Faraday reaction.In addition,the maximum specific capacitance of the symmetrical capacitor made from PC-CDs-1.5%reaches to 1782.5 F g^-1,.The specific capacitance could still maintain at 800 F g^-1 even at the current density of 6 A g^-1.The device has a high cycle life（87.8%retention after 10,000 charges and discharges）,demonstrating the good electrode catalytic performance and capacitance retention ability of the PC-CDs composite carbon material in the Faraday electrolyte system.（2）Under the concentrated sulfuric acid,the P-nitroaniline precursor experience rapidly voulum expansion and carbonlization to form the porous carbon intermediates With the help of monomolecular dispersion technology,ammonium nitrate and sulfur were uniformly mixed in the carbon intermediate.Under the laser treatment,sulfur-nitrosamine-carbon blasting reaction was initiated in the pore structure of carbon material,thus introducing abundant N and S doping sites.After graphitization and activation at high temperature,N-S co-doped porous carbon materials with high porosity and specific surface area were synthesized.Laser assisted treatment can not only increase the doping amount of N and S atoms,but also increase the number of graphitic-N doping sites and C-S-C doping sites,reduce the proportion of-SO_Xfunctional groups,thus improving the electrical conductivity,Faraday capacitance activity and catalytic activity of materials.Under the condition of 0.5 A g^-1in acidic electrolyte,the specific capacity of symmetrical capacitor can reach to 393 F g^-1.By adding KI as the Faraday addatives,the specific capacitance of the device can reach 780 F g^-1 at 2 A g^-1,which is～200%higher than that of the non-KI electrolyte device.This laser-assisted method can be used as a universal solution to introduce specific defect structures on the surface of carbon materials such as graphene and activated carbon,so as to improve its application in energy storage and environmental purification.（3）The p-nitroaniline was adopted as starting materials to prepare porous carbon via the sequent carbonization and activation.Aminoborane was introduced into porous carbon surface by adsorption and freeze drying.Then,the N and B co-doped porous carbon materials were obtained by laser treatment.This method can not only form rich and stable boron atom doping sites under the laser treatment,but also improve the porosity and graphitization degree of carbon structure under the joint action of laser and hydrogen gas flow.In the 1M H₂SO₄ electrolyte system,the specific capacitance of the electrode reaches to327 F g^-1,which is greatly improved compared with the pre-doping material,showing superior energy storage capacity.