Green activation method and natural N/O/S co-doped strategy to prepare biomass-derived graded porous carbon for supercapacitors

The sustainable development and high-value utilization of biomass energy were realized by the thermo-chemical method of converting waste biomass into porous carbon materials rich in functional groups and then used in supercapacitors. In this regard, a new method to obtain carbon materials was innovatively proposed in this study by the potassium acetate green activation method coupling natural heteroatom (N, O, S) co-doping strategy. Among them, the co-pyrolysis of spiral algae and bamboo successfully introduced heteroatom functional groups into the microstructure of the carbon materials, which opens up a simple, efficient, and green synthetic route for N/O/S co-doped porous carbon. The results indicated that BC-SA8 provided a capacitance of 320.4 F/g (0.5 A/g) as a carbon electrode in a three-electrode system, depending on its favorable sp2/sp3 hybridization, outstanding microstructure, and abundant heteroatom functional groups. In addition, the symmetric supercapacitor obtained using BC-SA8 exhibited 236.35 F/g at 0.25 A/g. At 10 A/g, SSC/BC-SA8 still had 94.29% capacitance retention after 10,000 cycles. The energy density of SSC/BC-SA8 is 8.21 Wh/kg and 5.42 Wh/kg at 62.5 W/kg and 5000 W/kg power density, respectively. Overall, this work proposed the extraction of heteroatom-rich porous carbon materials from natural biomass by the hybrid pyrolysis technique, laying the foundation for developing green, environmentally friendly, and sustainable heteroatom doping technology.