Preparation of nitrogen-rich porous carbon by microwave-assisted two-step co-pyrolysis of kapok wood and Chlorella vulgaris

Abstract

In this work, nitrogen-rich porous carbon with abundant pore size distribution was fabricated by microwave-assisted two-step co-pyrolysis of kapok wood (KW) with Chlorella vulgaris (CS), which revealed two nitrogen doping ways of CS as a green nitrogen source. The porous carbon K3C7PC obtained at a mixing ratio of 3:7 between KW and CS possesses the highest specific surface area (SSA) of 2909.78 m2/g, and its pore volume reaches 3.44 cm3/g. The weight loss curves show that the KW biochar retains some of the nitrogenous compounds produced by CS. The three-electrode test shows that the specific capacitance of KWPC obtained from the pyrolysis of KW is only 253.8 F/g, while the specific capacitance of K3C7PC reaches 380 F/g after 70% of CS is mixed with KW. Besides, the symmetric supercapacitors of K3C7PC exabits the maximum energy density of 8.09 Wh/kg at 125 W/kg power density, and after 10,000 cycles, the capacitance retention rate is still 98.49%. This work is convenient for directing the co-pyrolysis of lignocellulosic and algal biomass for the preparation of nitrogen-rich porous carbon.