| Porous carbon materials,especially porous carbon spheres（PCSs）,have been widely favored for their abundant pore structure,good electrical conductivity and controllable spherical morphology.In recent years,the controllable design of their structures and their application in energy storage devices have attracted a lot of attention.However,activation and surfactant auxiliary are still the main methods to improve the surface area and regulate the pore structure,morphology and composition.The structure regulation strategy based on non-activation and surfactant-free has practical significance for the preparation of PCSs and their applications in many emerging fields,such as energy conversion,catalysis,adsorption and so on.Here,the micro-and/or meso-carbon spheres with solid,hollow,soft yellow or multi-shell were prepared base on the controllable design of the molecular structure and the composition,morphology structure and pore structure for high supercapacitor performance,this strategy provides more reference paths for the controllable preparation of porous carbon spheres.First of all,a space-sacrificed pyrolysis strategy was applied for the preparation of solid microporous boron-doped carbon spheres（B-CSs）with improved surface area by regulating the molecular composition and the structure of carbon precursors,using triphenyl borate as carbon and boron co-source.The basic principle and process were demonstrated and analyzed.The as prepared B-CSs possessed a high surface area and boron content with uniform boron atoms distribution and high surface polarity,which contributes to the improvement of pseudo-capacitance.The optimal sample has a boron content of 1.38at%,surface area of 560 m2 g–1 and specific capacitance of 235 F g–1.This space-sacrificed pyrolysis may provide a new and extensible ideal for improving surface area of carbon materials especially for the B-CSs by regulating the structure of carbon precursors.Secondly,based on controlled condensation at molecular level,a surfactant-free"accelerated condensation"strategy based on temperature regulation was devised for the manufacture of hollow mesoporous CS（HMCS）with regulatable pore structure and shell core size.This strategy was to achieve the co-condense of silica（Si O2）and phenolic resin（RF）on Si O2 by adjusting the nucleation temperature to obtain matching of the hydrolysis/condensation rate of TEOS and resorcinol.The shell thickness and pore structure of HMCS can be effectively regulated by adjusting the ratio of homogeneous nucleation time of TEOS.The HMCS prepared based on this strategy have a maximum mesoporous size of 12.13 nm,BET specific surface area of 1236 m2 g-1.Efficient nitrogen doping can be easily achieved by changing monomer.The HMCS can also been obtained at a very short nucleation time of 0.5 h.The obtained HMCS have excellent supercapacitor performance.The capacitance of HMCS can reach 289 F g-1 at 1 A g-1,which was significantly higher than that of carbon spheres with microporous structure(179 F g-1),and the capacitance of NHMCS with nitrogen doping can reach 320 F g-1.The abundant pore structure and stable spherical morphology gave it an energy density of 9.6 Wh kg-1and a capacity retention of 92%.This strategy provides a new technique for the controllable and rapid manufacture of HMCS with different structures and compositions.Then,based on the effective control of condensation degree,a"time delay"strategy based on hydrolysis control without surfactants was proposed to accurately control the structure of PCSs.PCSs with different structures were obtained from hollow CS（HCS）to hollow mesoporous CS（HMCS）,and further to solid mesoporous CS（SMCS）and to yolk-shell mesoporous CS（YMCS）.The mechanism of this strategy was explained by analyzing the degree of hydrolysis/condensation of the single system,and based on this strategy,the boron/nitrogen co-doped mesoporous CS（BNHMCS）were prepared.The PCSs prepared based on this strategy have a mesoporous size of 11.32-12.09 nm and BET specific surface area of 676-828 m2 g-1.The electrode materials with good supercapacitor performance were obtained,especially the capacitance of YMCS and BNHMCS reached 272 F g-1 and 291 F g-1 at 1 A g-1.In the symmetric supercapacitors,YMCS has high capacity retention and the energy density of 8.9 Wh kg–1.This strategy provided a convenient method for the preparation of PCSs with precise structure regulation and effective doping.Finally,based on the design of spatial structure of carbon microsphere precursor,a"confined space"pyrolysis strategy based on surfactant-free and pyrolysis control was proposed.In this strategy,TPOS/TEOS was used as template to obtain core-shell spheres with the confined layer,then hierarchical multilayer mesoporous carbon spheres（DYS-MCS）were obtained by dual-confined.The confined capacity of the space confined layer was controlled by adjusting the ratio of silicates(n TPOS/TEOS),and the structure of PCSs were regulated.The formation mechanism,evolution process and effect of confined layer were discussed.Based on this strategy,the number and structure composition of shell can be easily adjusted by adding raw materials again and introducing boron/nitrogen source,and the multilayer carbon spheres and boron/nitrogen doped carbon spheres can be obtained.The large pore size and high specific surface area,as well as the further improved structure after doping,combined with the hierarchical pore structure,lay the foundation for obtaining superior supercapacitor performance.The maximum capacitance was 326 F g-1,and the capacity retention was above 53%even at 20 A g-1.Excellent cyclic stability and high energy density make it suitable for high performance electrode materials.Further doped carbon spheres show a promising application in more demanding fields. |
