Fast one-pot microwave preparation and plasma modification of porous carbon from waste lignin for energy storage application.

Because the commonly used two-step approach (carbonization followed by activation) usually produces microporous carbons and requires a long production duration, obtaining a low-cost porous-carbon-based supercapacitor with both high energy density and rate capability is a challenge. Herein, a more cost-effective one-pot approach via microwave heating in humidified N2 combined with water vapor plasma modification is proposed to obtain lignin-based porous carbon with a hierarchical and oxygen-enriched structure. Humidified microwave heating can produce hierarchical porous carbon with a high specific surface area (SBET) of 2866 m2 g-1 and high mesopore content of 68.16%. Water vapor plasma modification not only results in a further development of the porosity with an increase in SBET by 11.6% but also results in the doping of oxygen (up to 33.43%). These characteristics ensure a high energy storage capacity and an excellent rate capability for the prepared supercapacitor, which exhibits the highest specific capacitance of 254.6 F g-1 at 0.5 A g-1 with a retention rate of 75.6% at 10 A g-1. The results of this study confirm the good feasibility of the one-pot preparation approach combined with plasma modification for the effective use of waste lignin for advanced energy storage applications.