Multifunctional CaO template promotes the synthesis of natural N-doped hierarchical porous carbon for supercapacitors

N-doped porous carbon with reasonable pore size distribution is conducive to improving low specific capacitance and low ion transport efficiency. Natural N-doped hierarchical porous carbon (NNHPC) was synthesized by microwave-assisted heating using kapok tree and chlorella vulgaris as raw materials. CaO was used as a template to extend the pore channels and simultaneously enhance the retention of N atoms in NNHPC. The pyrolysis properties of the samples and surface functional groups of NNHPC were analyzed, revealing that CaO enhanced the creation of nitrogenous compounds in the coke by inhibiting protein nitrogen decomposition. It led to a 74.45 % increase in N atom retention. When the addition ratio of CaO to biomass is 1:10, the optimal sample NNHPC-1CaO exhibits the highest specific surface area (SSA) of 3117.73 m2/g, accompanied by a microporous volume of 0.71 cm3/g. Therefore, NNHPC-1CaO exhibits the highest specific capacitance of 429.18 F/g, which still achieves excellent rate performance with 69.53 % at 20 A/g. The symmetric supercapacitor achieves a best energy density of 11.01 Wh/kg at 125 W/kg.