Direct carbonization of sodium lignosulfonate through self-template strategies for the synthesis of porous carbons toward supercapacitor applications

Commercial supercapacitors rely on expensive porous carbon electrode materials. Therefore, it is essential to search for low-cost porous carbon electrode materials for next-generation supercapacitors. In this work, we produced lignin-derived porous carbon from alkalized sodium lignosulfonate. The carboxyl and phenolic hydroxyl are bonded with potassium ions in alkalized sodium lignosulfonate molecules. As a result, the introduced potassium ions on carboxyl and phenolic hydroxyl groups and sodium ions on sulfonate groups act as the porogens for preparing porous carbons. The alkalized sodium lignosulfonate is pyrolysis carbonized to produce porous carbon materials for asymmetric and symmetric supercapacitors. Developed pores inside the lignin-derived porous carbons are generated from the self-template role of the generated inorganic metal carbonates and metal sulfates. The introduced alkali metal ions in alkalized sodium lignosulfonate play extra roles of templates. Our work made a new paradigm shift that lignin could be transformed into porous carbon electrodes through self-template methodologies for future supercapacitor applications.