Interconnected\nHierarchical Porous Carbon from Lignin-Derived\nByproducts of Bioethanol Production for Ultra-High Performance Supercapacitors

Abstract

The\nadvent of bioethanol production has generated abundant lignin-derived\nbyproducts which contain proteins and polysaccharides. These byproducts\nare inapplicable for direct material applications. In this study,\nlignin-derived byproducts were used for the first time as carbon precursors to construct\nan interconnected hierarchical porous nitrogen-doped carbon (HPNC)\nvia hydrothermal treatment and activation. The obtained HPNC exhibited\nfavorable features for supercapacitor applications, such as hierarchical\nbowl-like pore structures, a large specific surface area of 2218 m² g^–1, a high electronic conductivity of\n4.8 S cm^–1, and a nitrogen doping content of 3.4%.\nHPNC-based supercapacitors in a 6 M KOH aqueous electrolyte exhibited\nhigh-rate performance with a high specific capacitance of 312 F g^–1 at 1 A g^–1 and 81% retention at\n80 A g^–1 as well as an excellent cyclic life of\n98% initial capacitance after 20 000 cycles at 10 A g^–1. Moreover, HPNC-based supercapacitors in the ionic liquid electrolyte\nof EMI-BF₄ displayed an enhanced energy density of 44.7\nWh kg^–1 (remaining 74% of max value) at an ultrahigh\npower density of 73.1 kW kg^–1. The proposed strategy\nmay facilitate lignin utilization and lead to a green bioethanol production\nprocess.