A novel approach for preparing in-situ nitrogen doped carbon via pyrolysis of bean pulp for supercapacitors

The preparation of activated carbon by complex and expensive nitrogen doping and activation process has been studied extensively. N-doped activated biochar or carbon material prepared from renewable and low-cost biomass has arisen more and more attention due to the hierarchical porous structure and abundant nitrogenous functional groups in the application of supercapacitors. Herein, a method for preparation of in-situ nitrogen doped activated carbon derived from bean pulp (BPC) by one-step carbonization and CO2 activation at 1073 K was proposed. The morphological structure, specific surface area (SSA), pore size and nitrogen-containing functional group compounds could be controlled by the adjustment of CO2 concentration. The maximum SSA could be up to 558.2 m(2) g(-1) for BPC. The N content increased from 5.0% to 10.0% with the increase of CO2 concentration from 0 to 50 vol%. In addition, pyridine, pyrrole, graphite, and nitrous oxide were detected and analyzed, in which pyridine and pyrrole nitrogen enhance the pseudocapacitance. A maximum specific capacitance of BPC-50 reached 106 F g(-1) at 0.25 A g(-1). The capacitance retention maintained 93% at 10 A g(-1) after 20,000 cycles in the symmetrical supercapacitor with a 6 M KOH electrolyte. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This study successfully prepared nitrogen-doped activated carbon derived from bean pulp using one-step carbonization and CO2 activation. By adjusting the CO2 concentration, the morphological structure, specific surface area, pore size, and nitrogen-containing functional groups could be controlled, achieving a maximum specific surface area of 558.2 m(2) g(-1) with excellent performance in supercapacitors.