A combination of heteroatom doping engineering assisted by molten salt and KOH activation to obtain N and O co-doped biomass porous carbon for high performance supercapacitors

For the conversion of high-valued carbon materials on energy application, the N and O co-doped biomass porous carbon (N/O-BPC) derived from waste eucalyptus bark was successfully synthesized via a combination of heteroatom doping engineering assisted by molten salt and KOH activation. The formation mechanism of optimized N/O-BPC with 1719.15 m2 g−1 surface area, 0.83 cm3 g−1 pore volume and 20.82% heteroatom content was investigated, and the supercapacitance performances of the obtained BPCs in different aqueous electrolyte were explored. In a three-electrode system, the N/O-BPC electrode exhibited an outstanding specific capacitance of 483.5 F g−1 at 0.5 A g−1 in the electrolyte of 1 M H2SO4. The N/O-BPC supercapacitor in the electrolyte of 1 M Na2SO4 delivered an energy density of 21.7 Wh kg−1 at 168.9 W kg−1, and obtained 83.1% capacitance retention after 10,000 GCD cycles at 5 A g−1. Furthermore, the assembled N/O-BPC symmetric quasi-solid-state supercapacitor reached an excellent energy density as high as 21.0 Wh kg−1 at 170.0 W kg−1. This work can serve as an effective strategy to prepare advanced biomass-derived porous carbon for electrochemical energy storage.