Structrually Design Synthesis Of Porous Hollow Carbon Spheres And Their Application In Supercapacitors

Porous hollow carbon spheres shows excellent performance as electrode materials of supercapacitor due to its hollow structure,high surface area and superior electrical conductivity.The designing synthesis,surface modification and functionalization of porous hollow carbon spheres are the hot points of current research.Herein,porous hollow carbon spheres was obtained by the pyrolysis of core-shell structured phenolic-melamine resin composite material,by using melamine resin as template.The effects of solvent,template and element doping on the morphology and properties of carbon spheres were studied,and all the prepared carbon materials were tested as electrode materials of supercapacitor.(1)Nitrogen doped hollow carbon spheres(NHCSs)with tunable surface morphology have been prepared through one-pot carbonization method by using melamine-formaldehyde spheres as template and resorcinol-based resin as carbon precursor in ethanol-water solution.Well-dispersed NHCSs with particle size of 800 nm were obtained and the surface of NHCSs turn from smooth to tough,wrinkled,and finally concave by increasing the ethanol concentration.The fabricated NHCSs possessed high nitrogen content(3.99-4.83%)and hierarchical micro-dual mesoporous structure with surface area range of 265-405 m2 g-1 and total pore volume of 0.18-0.29 cm3 g-1,which contributed to high specific capacitance,excellent rate capability and long cycle life.(2)Nitrogen-doped hollow carbon spheres(NHCSs)with ordered mesopores have been prepared by a one-pot carbonization method using melamine-f’ormaldehyde spheres as template,F127 as surfactant and 3-aminophenol-formaldehyde resin as carbon precursors.F127 was also a size-controlling agent for the melamine-formaldehyde spheres.The uniform NHCSs show tunable particle size ranging from 500 nm to 1600 nm with shell thickness ranging from 90 to 290 nm.NHCSs at particle size of’ 800 nm show favorable features for electrochemical energy storage such as high surface area of 657 m2 g-1,ordered mesoporous structures and high nitrogen doping(5.33%).With respect to the multiple synergistic effects of these features,a significant specific capacitance(181 F g-1 at 0.5 A g-1,145 F g-1 at 20 A g-1)with superior stability(92%maintenance after 5000 cycles)in a three-electrode system and capacitance of 162 F g-1 at 0.5 A g’ and high cycling life stability(9%loss after 5000 cycles)in the symmetric solid-state supercapacitor device are acquired after measurement.(3)Nitrogen-doped hollow carbon spheres were synthesised using melamine resin spheres as templates,resorcin-formaldehyde resin as carbon precursor and melamine as nitrogen sources,and the influences of nitrogen doping on the morphology and electrochemical properties were evaluated.The nitrogen doping amount reach up to 5.4%with asurface area of 550 m2 g-1,and specific capacitance of 148 F g’ at curren dendity of 0.5 A g-1.The electrode materials prepared by the carbon spheres showed a superior rate performance and cyclic stability,a retention of 60%when the current densities raise from 0.5 A g-1 to 20 A g-1,and only 6%capacitance loss after 5000 recycles.