The exploration of efficient utilization of lignin is very important and necessary for the applied biomass energy and sustainable development. In this work, hydrolyzed lignin residue, contenting more than 70% lignin, obtained from acid hydrolysis of sorghum straw was reused to synthesized ultrahigh surface area and hierarchical porous activated carbon for the first time. As-prepared nanomaterial (HLAC-1) presented unusual features such as unique interconnected porous structure, ultrahigh surface area (ca.2927 m2 /g), large total volume (ca.1.65 cm3 /g) and a high graphitization degree. Furthermore, as the electrode material for supercapacitor, HLAC-1 also exhibited remarkably high capacitance (400 F/g at 0.5 A/g) and superior cycling stability (99.1％ capacity retention after 20,000 cycles at 5 A/g) in 6M KOH aqueous electrolyte. A high energy density of 9.53 Wh/kg at a powder density of 53.22 W/kg (6.96 Wh/kg at a powder density of 2532.39 Wh/kg) have been achieved in KOH aqueous supercapacitors, indicating that the conversion of hydrolyzed lignin residue from activated carbon is very attractive and promising for the application in supercapacitor.
Keywords hydrolyzed lignin, activated carbon, ultrahigh specific surface area, hierarchical porous structure, supercapacitor