Synthesis of Biomass-Derived Nitrogen-Doped Porous Carbon Nanosheests for High-Performance Supercapacitors

Graphene-like two-dimensional carbon nanosheets with properly modulated compositions and porosity are of particular importance for robust capacitance harvesting. Nevertheless, the large-scale and cost-effective production of such nanostructures still remains a great challenge. Herein, we innovatively produce nitrogen-doped porous carbon nanosheets using pine nut shells, an abundant biomass waste, as the precursor, under the synergetic effect of KOH and melamine during the activation process. The sole activation of the precursors with KOH can produce only traditional activated carbon particles of several micrometers, while interestingly, the extra introduction of melamine results in nitrogen-doped porous carbon nanosheets possessing high tunability. By construction of a two-electrode configuration, the supercapacitors with optimal nanosheets as the electrode materials can deliver a superior specific capacitance of 324 F g(-1) at 0.05 A g(-1), outstanding rate capability of 258 F g(-1) at 20 A g(-1), and extraordinary cyclic stability of 94.6% after 10 000 cycles at 2 A g(-1) in an aqueous electrolyte of 6 M KOH. Such a facile strategy proposed here may contribute to new possibilities of synthesizing graphene-like porous carbon nanosheets in a sustainable manner for energy-related applications.