N, B co-doped porous carbon materials with high heteroatom content derived from Pleurotus eryngii for high-performance symmetrical supercapacitors

N and B co-doped carbon materials were prepared using urea and H 3 BO 3 as activators and Pleurotus eryngii as the carbon source. Structural characterization shows that the heteroatom content of PENB (co-modified by urea and H 3 BO 3 ) is as high as 62 %, which is much higher than that of carbon materials modified by a single activator. The specific surface area of PENB is 2.2 times that of PEB (modified only by H 3 BO 3 ) and 127.4 times that of PEN (modified only by urea). The high specific surface area of PENB can provide more active sites. The excellent structure of PENB can be attributed to the fact that urea and H 3 BO 3 retain heteroatoms in the reaction system through neutralization reaction, which promotes the contact between heteroatoms and biomass, thereby enhancing the etching effect of heteroatoms on carbon materials. In addition, N and B atoms can induce amorphous carbon materials to produce graphene microcrystals, which can enhance the electronic conductivity of PENB. Interestingly, this method of increasing the content of heteroatoms and generating graphene is also applicable to other biomass. Electrochemical tests show that PENB exhibits the highest electrochemical performance. The symmetrical supercapacitor (SSC) assembled with PENB has an energy density of 8.8 Wh kg −1 at a power density of 400 W kg −1 . After 10,000 cycles, the capacitance retention rate is 100 %. This work provides a new universal strategy to improve the heteroatom content of carbon materials and the preparation of graphene, which can well cope with the energy crisis.