Insights into Gas-Exfoliation and the In-Situ Template Mechanism of Zinc Compound for Lignin-Derived Supercapacitive Porous Carbon

The large-scale production of porous activated carbon is plagued by the overuse of corrosive activators, so developing a green and mild activation strategy is technologically urgent and meaningful. Herein, two gentle activators (ZnCO3 and ZnC2O4) and a traditional corrosive agent (ZnCl2) are utilized to activate lignin for porous carbons, and the microstructures and electrochemical properties of the carbons are systematically investigated. By tracking the evolution of the carbonized products through TG-MS, in-situ FT-IR, and other characterization methods, the gas-exfoliation and in-situ template functions of ZnCO3 and ZnC2O4 are proposed. It was found that the pyrolysis synergistic effect between ZnC2O4 and lignin boosts the decomposition of oxygen-containing groups, playing a pivotal role in the fabrication of hierarchical porous carbon with crumpled nanosheets. The electrochemical properties of the carbons are closely correlated to their porous structures. Benefiting from the well-developed crumpled lamellar units, the hierarchical porous carbon activated by ZnC2O4 has a high specific surface area and good conductivity. Consequently, it exhibits a higher capacitance than the microporous carbon activated by ZnCl2 and the mesoporous carbon activated by ZnCO3.