Controlled Preparation And Application Of Nitrogen-doped Carbon Spheres

The nitrogen-doped carbon material can significantly change the elemental composition and surface activity,so that the use of the carbon material in electrode materials,adsorption,catalysis,and the like can be greatly improved.To date,most nitrogen-doped carbon material have been prepared by a multi-step template process where the spherical template is first coated with polymerizable nitrogen-containing carbon precursors including dopamine,pyrrole,acetonitrile,ethylenediamine,etc.,then carbonized and subsequently template removal process.Obviously,all of the above methods involve tedious procedures and organic toxic chemicals that are complex,time-consuming and expensive and are not suitable for scale-up production and practical applications.In this research,a green route to directly convert biomass to nitrogen-doped hollow carbon nanospheres?N-HCSs?was reported,where only glucose and glucosamine were used as the precursors and an aerosol-assisted process was employed.In the process,amino groups of glucosamine triggered the co-assembly between glucose and glucosamine,resulting in the structural evolution of hollow structures.The aerosol-based technology ensures the obtained particles with the spherical morphology and in the nanoscale size range.The as-prepared materials have been thoroughly characterized by SEM,TEM,HAADF-STEM,EELS mapping,XPS,XRD,Raman and nitrogen adsorption.Owing to the unique structural and surface properties,the resultant N-HCSs exhibited excellent electrochemical properties for energy storage,including the high specific capacitance of 266 F g^-1 at 0.2 A g^-1,long cycling stability with 96.8%of capacitance retained after 3000 cycles and fast charge-discharge process.This discovery could be adapted to guide design and synthesis of a variety of hollow materials from biomass for wider applications in the environment and energy fields.In addition,we replaced the glucosamine sheath with 3-aminopropyltriethoxysilane?APTES?as a precursor,and nitrogen-doped porous carbon was prepared on the basis of other unchanged conditions.It was characterized by SEM,TEM,XPS,and nitrogen adsorption.Due to its unique structure and surface properties,the synthesized N-PCSs exhibit excellent performance in the adsorption of heavy metals.Nitrogen doping can modulate the physical/chemical properties of the sorbent,such as morphology,defects,and surface functionality.The effects of N content,pH value,Cr?VI?concentration,treatment time and adsorbent dose were systematically studied and the results showed that the excellent Cr?VI?removal performance could be attributed to the nitrogen dopant and porous structure.The N dopant on the carbon surface can increase its charge density,and then increase Cr?VI?removal,much higher than undoped samples.The results show that it benefits Cr?VI?removal with the increasing of N-doping amount,the decreasing of pH.It can reach 100%Cr?VI?removal with the dosage of 5 g L^-1,which the Cr?VI?initial concentration is 60 mg L^-1.And the removal can still reach 70%after recycled 5 times.