Structural evolution of porous graphitic carbon nanosheets based on quinonyl decomposition for supercapacitor electrodes

Porous graphitic carbon nanosheets (MNC-x) with well-developed porosity and appropriate heteroatom doping are prepared by directly carbonizing sodium lignosulfonate in inert atmosphere. Interestingly, MNC-900 prepared at 900 degrees C shows sharp increases in specific surface area, carbon to oxygen atom ratio, graphitization degree and electrical conductivity compared with MNC-800 prepared at 800 degrees C, which are mainly attributed to the quinonyl decomposition accompanied by formation of graphitic carbons. The high oxygen content (20.1 at. %) and mesopore ratio (71.0%) of MNC-800, large specific surface area (1400 cm(3) g(-1)) and superior conductivity (2208 S m(-1)) of MNC-900 make them suitable for supercapacitor electrodes in aqueous and organic electrolytes, respectively. Specifically, MNC-800 electrode shows large specific capacitance (196 F g(-1) at 0.25 A g(-1)), superior rate capability (170 F g(-1) at 20 A g(-1)) and outstanding cycling stability (96% capacitance retention after 10,000 cycles) in symmetrical supercapacitor using 3 M KOH electrolyte. For MNC-900 based symmetrical supercapacitor with 1 M (C2H5)(4)NBF4/PC electrolyte, an impressive energy density of 30.2 Wh kg(-1) at a power density of 309.8 W kg(-1) is achieved, which remains 15.2 Wh kg(-1) even at 9.9 kW kg(-1).

Automated summary

Porous graphitic carbon nanosheets with appropriate heteroatom doping were prepared by carbonizing sodium lignosulfonate in an inert atmosphere. The MNC-900 prepared at 900 degrees C showed significant increases in specific surface area, carbon to oxygen atom ratio, graphitization degree, and electrical conductivity compared to MNC-800 prepared at 800 degrees C. High oxygen content and mesopore ratio of MNC-800, along with large specific surface area and superior conductivity of MNC-900, make them suitable for supercapacitor electrodes.