Tetra-heteroatom self-doped carbon nanosheets derived from silkworm excrement for high-performance supercapacitors

Carbon materials are deemed to be competitive candidate electrode materials for energy storage systems. It is still a great challenge to explore advanced carbon-based electrode materials for high-performance super capacitors by a facile, economical and efficient method. In this work, N-, P-, S-, O-self-doped carbon nanosheets with high surface area and well-developed porosity are successfully prepared by pyrolysis carbonization and post KOH activation from silkworm excrement, a novel abundant, low-cost and eco-friendly agricultural waste. Thanks to their unique multi-heteroatom doping and porous structure, the obtained carbon materials exhibit high charge storage capacity with a specific capacitance of 401 F g(-1) at a current density of 0.5 A g(-1) in 6 M KOH and good cycling stability with a capacitance retention of 93.8% over 10000 cycles. A symmetric super capacitor device using 1 M Na2SO4 aqueous solution as the electrolyte can deliver a specific capacitance of 41.7 F g at a current density of 0.5 A g(-1), and a high energy density of 23.17 Wh kg(-1) at a power density of 500 W kg(-1) with a wide voltage window of 2.0 V. This work develops a new strategy to produce favorable carbon-based electrode materials for supercapacitors with high electrochemical performances.