Green Synthesis Of Biomass Derived Porous Carbon By New Template Methods And Their Application As Supercapacitor Electrodes

Porous carbon?PC? is rich pores and stable performance and is used widely as the supercapacitor electrodes.The traditional synthesis of porous carbon with micro-and mesopores includes chemical activation method and template method.Some problems involve in above process including complex experimental procedure,serious pollution and equipment corrosion.Therefore,serials of PC have been prepared using green recyclable neutral salt and biomass as the self-template or/and the self-activation agent.The morphologies and structures of the products as well as the electrochemical properties of PCs for supercapacitors have been investigated in detail.A novel class of lignin-based PC for supercapacitor electrode is successfully fabricated using lignin as the carbon precursor and NaCl as the template by reflux at low temperature and calcination at high temperature.The results indicate that the porous structures of the obtained samples can be regulated by varying the calcination temperature,where the surface area and pore volume of samples firstly increased then decreased with the increase of the temperature.As a result,the specific surface area of the obtained sample can be tailored in the range of 548⁶00 m² g^-1.PC calcinated at 700 ? with the largest surface area exhibits the highest specific capacitance of 252 F g^-1 and an effective areal capacitance of 31.2?F cm^-2in 6 M KOH solution.NaCl template can be cycled by washing from the products.This paper proposes a green method for the synthesis of highly value-added porous carbon from waste materials.A novel class of N-doped carbon has been successfully fabricated using prawn shell as both carbon precursors and self-templates.CaCO₃ in the shell has natural well-defined macropore channels,and it can be decomposed into CaO as the active agent.The specific surface area of the obtained carbon materials ranging from 117.6to 1114 m² g^-1 can be facilely controlled via adjusting the content of CaCO₃ in the shrimp shell.And the N content ranging from 3.6⁴.26 wt.%can be tailored after pyrolysis of shrimp shell,which is benefit to the final electrochemical property.The materials named as C-25% CaCO₃ pyrolyzed at 900 ? for 3 h shows the higher surface area(1114 m² g^-1)and the suitable N content of 3.6 wt.% in the obtained carbons.The supercapacitor performance of C-25%CaCO₃ was evaluated in 6 M KOH electrolyte.C-25%CaCO₃ sample demonstrates the largest specific capacitance of 328 F g^-1 at a current density of 0.05 A g^-1.The best cycle stability with 271 F g^-1 at1.0 A g^-1 after outstanding cycling stability with 96.0% capacitance retention after 5000 cycles.Its specific energy density and power density are 30 Wh kg^-1 and 1465 W kg^-1 in two-electrode cell,respectively.The high electrochemical performance can be attributed to the synergistic effects of the double layer capacitance formed by the hierarchical pores and the pseudocapacitance formed by the N doping.