Biomass Derived N-Doped Porous Carbon Made from Reed Straw for an Enhanced Supercapacitor

Abstract

Developing advanced carbon materials by utilizing biomass waste has attracted much attention. However, porous carbon electrodes based on the electronic-double-layer-capacitor (EDLC) charge storage mechanism generally presents unsatisfactory capacitance and energy density. Herein, an N-doped carbon material (RSM-0.33-550) was prepared by directly pyrolyzing reed straw and melamine. The micro- and meso-porous structure and the rich active nitrogen functional group offered more ion transfer and faradaic capacitance. X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) measurements were used to characterize the biomass-derived carbon materials. The prepared RSM-0.33-550 possessed an N content of 6.02% and a specific surface area of 547.1 m2 g−1. Compared with the RSM-0-550 without melamine addition, the RSM-0.33-550 possessed a higher content of active nitrogen (pyridinic-N) in the carbon network, thus presenting an increased number of active sites for charge storage. As the anode for supercapacitors (SCs) in 6 M KOH, RSM-0.33-550 exhibited a capacitance of 202.8 F g−1 at a current density of 1 A g−1. At a higher current density of 20 A g−1, it still retained a capacitance of 158 F g−1. Notably, it delivered excellent stability with capacity retention of 96.3% at 20 A g−1 after 5000 cycles. This work not only offers a new electrode material for SCs, but also gives a new insight into rationally utilizing biomass waste for energy storage.

Keywords

• biomass
• supercapacitors
• nitrogen doping
• melamine
• porous carbon