Preparation Of Nitrogen And Sulfur Doped Porous Carbon Spheres And Their Electrochemical Prepertries

As a commonly used electrode material,carbon material has a relatively low specific capacitance and energy density,which limits its application.Therefore,in order to improve the existing defects of the material,the hydrothermal method is adopted by the method of doping modification of heteroatoms.Combined with the sol-gel method and hydro-thermal method,a series of heteroatom-doped porous carbon spheres with excellent electrochemical properties were prepared.The structural characteristics,microstructure and elemental composition of the materials were analyzed by N₂ adsorption/desorption,Fourier transform infrared spectroscopy,scanning electron microscopy,XRD and XPS.Its electrochemical properties were investigated by the cyclic voltammetry and constant current charge and discharge methods.Nitrogen-containing polymeric microspheres were prepared by hydrothermal method and sol-gel method by using resorcinol and formaldehyde as carbon source,guanidine hydrochloride as nitrogen source and F127 as soft template.After high temperature carbonization,a group of nitrogen-doped carbon spheres were obtained.Porous carbon spheres（NMCS-x）have a large specific surface area（590.8 m²/g⁸51.5m²/g）and a high total pore volume（0.33 cm³/g⁰.63 cm³/g）.The nitrogen content is relatively high（3.14%⁵.38%）,the nitrogen is mainly in the form of pyridinium nitrogen and graphitic nitrogen.When the molar ratio of guanidine hydrochloride to resorcinol was 8:1,the carbon sphere NMCS-8 prepared the best performance.:the specific capacitance reached 252 F/g at a current density of 10 mA/g,and after 1000cycles,the capacitance retention was 97.2%.The synergistic effect of the two elements can make the material have better electrochemical performance.Therefore,a set of nitrogen/sulfur co-doped nanoporous carbon spheres was prepared by using thiourea as nitrogen source and sulfur source,and The group of nitrogen/sulfur co-doped porous carbon spheres（NSCS-y）are all nanoparticles with spherical structure and good dispersibility.Their specific surface area（637.9 m²/g⁷19.8 m²/g）and total pore volume（0.35 cm³/g⁰.40 cm³/g）were higher.From the XPS of NSCS-1,the N and S elements had been doped into the carbon material,and the contents were 1.43%and 1.1%,respectively,and N is mainly present in the form of graphite nitrogen.When the molar ratio of guanidine hydrochloride,thiourea and resorcinol was 2:1:1,NSCS-1 had excellent electrochemical performance:the specific capacitance was 400 F/g at a current density of 10 A/g.After 1000 cycles,the specific capacitance changed to 378.3 F/g,and the capacitance retention rate was94.6%.In order to further increase the nitrogen content,nitrogen/sulfur polymerization microspheres were prepared by using guanidine hydrochloride and thiourea as nitrogen source and sulfur source.A set of mixed nitrogen/sulfur co-doped porous carbon spheres（NSCS-GxTy）were obtained,which all showed regular spherical particles.The surface of the sphere was smooth and the whole surface was dispersed.The specific surface was 594.8 m²/g⁸61.2 m²/g,total pore volume was 0.33 cm³/g⁰.45 cm³/g.The N and S elements had been doped into the carbon material from the XPS of NSCS-G2T1,and the contents were 2.63%and 0.8%,respectively,and N was mainly present in the form of pyrrole nitrogen.When the molar ratio of guanidine hydrochloride,thiourea and resorcinol was 2:1:1,NSCS-G2T1 had excellent electrochemical performance:specific capacitance was 449 F/g at 10 A/g current density,after 1000cycles,the specific capacitance change was 430.6 F/g,and the capacitance retention rate was 95.9%.