Green preparation of hierarchical porous carbon with tunable pore size for supercapacitors

It is attractive to use green activators to prepare hierarchical porous carbon with controllable pore size distribution. Herein, we attempted plant ash as the activator to prepare hierarchical porous carbon through high-temperature carbonization and activation. The pore size of the obtained porous carbon varies from 1 to 7 nm with temperature. It has a high specific capacitance (387.8 F/g at 1 A/g) in 6 M KOH, showing high rate performance (capacitance retention rate of 73.2%, from 1 to 10 A/g). Then, it also exhibits excellent cycle stability after 10,000 cycles. The assembled symmetrical supercapacitor (PC-6/PC-6) has a high energy density of 23.25 Wh/kg in 1 M Na2SO4 solution when the power is 450 W/kg. In short, biomass as the green activator achieves high specific capacitance and excellent rate performance for the first time in supercapacitors. This work provides ideas for the green preparation of porous carbon with controlled pore size distribution.