Preparation Of Heteroatom-Doped Carbon Materials And Its Electrochemical Properties

Carbon materials are the most common supercapacitor electrode materials and play a very important role in the application of supercapacitors.Among all the carbon materials,mesoporous carbon materials are considered to be a ideal electrode materials for supercapacitors due to their large specific surface area,good stability and electrical conductivity.However,carbon materials have some problems such as poor rate performance and low specific capacitance,which can be solved by introducing heteroatoms into carbon materials.Benzoxazine is a promising carbon precursor because of its good molecular design flexibility,which can introduce heteroatoms into the carbon skeleton.In this paper,the heteroatom doped ordered mesoporous carbon materials were synthesized by hard template method using benzoxazine as carbon precursor and mesoporous molecular sieve(SBA-15)as template,and the electrochemical performance were studied.The main research contents are as follows:The thiourea-type benzoxazine-based nitrogen/sulfur co-doped carbon material(thiourea-NSCM)was prepared with thiourea-type benzoxazine as carbon precursor and SBA-15 as template.It was characterized by FTIR,SEM,TEM,XRD,N2 absorption/desorption and XPS.The test results show that the carbon materials successfully replicate the worm-like ordered mesoporous structure of template,with the specific surface area of 1179-1407 m2/g,average pore diameter of 7.7-9.3 nm,and pore volume of 2.4-2.9 cm3/g.Moreover,nitrogen and sulfur elements are successfully incorporated into carbon materials.The electrochemical properties of samples were investigated by CV and GCD.The effects of heating rate,immersion time,carbonization temperature and electrolyte on the properties of materials were also investigated.From the electrochemical test results,the highest specific capacitance of carbon materials is 604 F/g at the current density of 0.5 A/g in the H2SO4 electrolyte.When the current density increases to 10 A/g,there is still a high specific capacitance of 416 F/g,which the capacitance retention rate is 68.9%,indicating the good rate performance.At the current density of 5 A/g,the capacitance retention rate is 93.6%after 2000 times charge and discharge cycles,indicating that the carbon materials have excellent cycle stability.The aniline-type benzoxazine-based nitrogen/sulfur co-doped carbon material(aniline-NSCM)was prepared with sulfur-containing aniline-type benzoxazine as carbon precursor and SBA-15 as template.FTIR confirms the formation of benzoxazine monomer;SEM and TEM test results show that the materials partially replicate the worm-like structure of template;XRD analysis show that the pore structure of carbon materials is ordered;XPS characterization results indicate that the heteroatorns are successfully doped into the carbon materials;From the N2 absorption/desorption,the carbon materials are mesoporous structure,and have the large specific surface area(751-1171 m2/g)and pore volume(1.5-2.1 cm3/g),and the pore size distribution is uniform(6.39-8.52 nm).The effects of heating rate,immersion time,carbonization temperature and heteroatoms on the properties of the materials were investigated.The electrochemical properties of the samples were investigated by CV and GCD.The test results show that the specific capacitance of the material is 642 F/g at the current density of 0.5 A/g in the H2SO4 electrolyte,which is higher than the ordered mesoporous carbon material with undoped sulfur atom(aniline-NCM is 481 F/g).When the current density is 10 A/g,there is still a high specific capacitance of 436 F/g,which the capacitance retention rate is 67.9%,indicating the excellent rate performance.At the current density of 5 A/g,the capacitance retention rate is 95.2%after 2000 times charge and discharge cycles,which has the excellent cycle stability.