Three-Dimensional Hierarchical Porous Carbon with High Oxygen Content Derived from Organic Waste Liquid with Superior Electric Double Layer Performance

The organic waste liquid produced in the production of vitamin C is an acidic pollutant which is difficult for effective treatment and utilization, and lignin is an abundant biopolymer with abundant oxygen-containing groups. In this study, organic waste liquid and lignin are used as precursors for preparing oxygen-rich hierarchical porous carbon with a three-dimensional structure by synergistic reaction and activation. The obtained hierarchical porous carbons have a high specific surface area (3111.6 m 2 g –1 ) and high oxygen content (13.8 wt %). As the electrode material for an electric double layer capacitor, hierarchical porous carbon exhibits high specific capacitances (428 F g –1 at 0.04 A g –1 ) and excellent capacitance retention of 96% after 12 000 cycles under a two-electrode system. Meanwhile, its energy density is up to 12 Wh kg –1 . The excellent electrochemical performance can be attributable to the rational pore structure and rich oxygen functional groups of hierarchical porous carbon, so it is a promising carbon-based electrode material for electric double layer capacitor. Thereby, this paper provides a practical and green strategy for the large-scale production of porous carbon and the value-added utilization of organic waste liquid and lignin.