Nitrogen self-doped hierarchical porous carbon via penicillin fermentation residue (PR) hydrothermal carbonization (HTC) and activation for supercapacitance

The safe disposal and resource utilization of biomass waste are of great significance. For the first time, we have prepared penicillin fermentation residue (PR) N self-doped porous carbon through hydrothermal carbonization (HTC) combined with activation. Mild HTC method keeps stable carbon skeleton, rich nitrogen and oxygen functional groups. The hydrochar is activated as a precursor material to realize high specific surface area and naturally doped nitrogen. At 600 degrees C, the hierarchical porous carbons obtained with KOH and ZnCl2 as activators are BC@KOH600 and BC@ZnCl(2)600, with specific surface areas of 615.68 m(2)/g and 792.58 m(2)/g, respectively. The porous carbon prepared with ZnCl2 as an activator has higher N content than KOH. BC@ZnCl(2)600 has 4.75% N content, among which Pyridine-N is up to 36%. The BC@KOH600 and BC@ZnCl(2)600 supercapacitors have specific capacitances of 160.3 F/g and 209.2 F/g at 1.0 A/g in the three-electrode system, respectively, which display excellent rate performance and cycle stability. The BC@KOH600 and BC@ZnCl(2)600 symmetric supercapacitor, constructed with a two-electrode configuration, shows an energy density of 8.55 Wh kg(-1) and 8.79 Wh kg(-1) respectively and outstanding capacitance retention of 91.01% and 87.98% after 10,000 charge-discharge cycles at 5.0 A/g in an aqueous 6 M KOH electrolyte system. These results demonstrate a very effective method for the preparation of porous carbon using antibiotic residue for supercapacitors, which also provides a solution for the treatment of similar hazardous biomass wastes. (C) 2022 Published by Elsevier B.V.