From onion skin waste to multi-heteroatom self-doped highly wrinkled porous carbon nanosheets for high-performance supercapacitor device

Herein, we report the synthesis of N, S, P-self-doped porous and wrinkled graphene-like carbon nanosheets derived from the abundant waste onion skin via carbonization and activation strategy. The optimized onion skin derived carbon (OnC-900) exhibits highly wrinkled graphene-like morphology and multi-heteroatom doping without any external dopants is confirmed via field emission scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. The OnC-900, acting as a supercapacitor electrode, exhibits excellent specific capacitance of 478 F g(-1) at a current density of 1 A g(-1) and maintains 241.7 F g(-1) even at 6.7 A g(-1) in the three-electrode cell indicating its excellent rate capability. The assembled symmetric supercapacitor device using aqueous neutral electrolyte (1 M Na2SO4) delivers outstanding specific energy of 17 Wh kg(-1) with a wide potential window up to 1.4 V. The device also exhibits excellent cyclic stability by retaining 93% of initial capacitance over 10,000 cycles at a current density of 3 A g(-1). This enhanced performance of the electrode is mainly due to the high specific surface area and the heteroatom co-doping that provides improved surface wettability by polarized surface, induced pseudocapacitance effect, and improved electronic conductivity. These results demonstrate that onion waste derived multi-heteroatom co-doped graphene-like carbon nanosheets have great potential for renewable and sustainable energy storage devices.

Automated summary

The study presents the synthesis of N, S, P-self-doped porous and wrinkled graphene-like carbon nanosheets from waste onion skin, exhibiting excellent supercapacitor performance with high specific capacitance and good rate capability. The symmetric supercapacitor device assembled using these materials shows outstanding specific energy and cyclic stability, indicating great potential for renewable and sustainable energy storage devices.