Synthesis And Electrochemical Performance Of N/O Co-Doped Porous Carbon Derived From Schiff-Base Polymer

In recent years,carbon materials have wide application prospects in energy storage,molecule adsorption,catalysis,sewage treatment and other fields because of their excellent chemical stability,abundant sources,environmental friendliness,and ease of industrialization.In the field of supercapacitors,carbon has been widely studied as a conventional electrode material.In most studies,N/O doping has been used as a simple and efficient strategy to improve the electrochemical performance of carbon materials.Therefore,increasing the content of N/O elements in carbon materials has become a research hotspot in the development of carbon electrode materials for high-performance supercapacitors.In this thesis,based on a new porous schiff base polymer prepared by a simple and efficient synthesis method,a series of N/O doped carbon materials and high-nitrogen doped carbon materials were developed by regulating the carbonization conditions and the types of activat ion reagents.The main researches are as follows:1)In this section,N/O co-doped porous carbons（DQPACs）were prepared by the classic carbonization/KOH activation two-step method using a novel highly crosslinked schiff base polymers（DQPA）,which was synthesized by a facile,low-cost,high-yield polymerization between 2,5-dihydroxy-1,4-benzoquinone and p-phenylenediamine.The optimal material（DQPAC-A700）exhibits abundant micropores,large specific surface area(1659.97 m² g^-1),and a high level of N/O doping contents（as high as 4.09 wt.%and 10.84 wt.%,respectively）.These advantages endow DQPAC-A700 with the ideal electrochemical properties.As a result,the DQPAC-700 delivers the optimal specific capacitance of 292 F g^-1 at the current density of 0.5 A g^-1.Even if the current density is increased to 50 A g^-1,the specific capacitance still remians at 57.2%,showing an excellent rate performance.Meanwhile,the symmetric supercapacitor prepared by 6M KOH solution as electrolyte show a high cycling stability(capacitance retention up to 96%after 20,000cycles at 5 A g^-1)and a good specific capacity(162 F g^-1at current density of 0.2 A2)High specific surface area,high nitrogen doping and high yield are considered as the key requirements for the realization of high-performance porous N-doped carbon materials.However,the preparation of such materials is rarely reported.Therefore,in this section,a type of porous carbon materials with high specific surface area,good porisity structure and ultrahigh nitrogen doping were synthesized by"one-step C u C l₂ activation"using porous Schiff-Base polymer（DQPA）as the precursor and low corrosive C u C l₂ as the activation reagent.Subsequently,we compared the effect of activation temperature on the morphology and composition of the final material,and explored the mechanism of Cu C l₂activation of carbon material using XRD technology.As a result,the low corrosiveness of Cu C l₂ ensures that the carbon material is not overetched during activation,as well as reducing the destruction of the carbon skeleton and the loss of heteroatoms.Therefore,the obtained optimal carbon material C u-DBPC-700 not only maintains a high synthesis yield（58%）and the original nanosheet structure,but also has a high specific surface area(2266.02 m²g^-1)and excellent nitrogen doping（14.44%）.The electrode derived from Cu-DBPC-700 displays the optimal specific capacitance up to 286 F g^-1 at current density of 0.5 A g^-1using 6M KOH electrolyte.In addition,the symmetrical supercapacitors based on C u-DBPC-700 exhibit excellent cyclic stability（the specific capacitance remains 96% after 10000 cycle）.