Interconnected Hierarchical Porous Carbon from Lignin-Derived Byproducts of Bioethanol Production for Ultra-High Performance Supercapacitors

The advent of bioethanol production has generated abundant lignin-derived byproducts which contain proteins and polysaccharides. These byproducts are inapplicable for direct material applications. In this study, lignin-derived byproducts were used for the first time as carbon precursors to construct an interconnected hierarchical porous nitrogen-doped carbon (HPNC) via hydrothermal treatment and activation. The obtained HPNC exhibited favorable features for supercapacitor applications, such as hierarchical bowl-like pore structures, a large specific surface area of 2218 m2 g–1, a high electronic conductivity of 4.8 S cm–1, and a nitrogen doping content of 3.4%. HPNC-based supercapacitors in a 6 M KOH aqueous electrolyte exhibited high-rate performance with a high specific capacitance of 312 F g–1 at 1 A g–1 and 81% retention at 80 A g–1 as well as an excellent cyclic life of 98% initial capacitance after 20 000 cycles at 10 A g–1. Moreover, HPNC-based supercapacitors in the ionic liquid electrolyte of EMI...