Preparation of porous agro-waste-derived carbon from onion peel for supercapacitor application

Agro-waste-derived porous carbon has received more attention as electrode material for high-performance supercapacitor application due to its diversity and reproducibility. Herein, hierarchical porous carbon was successfully synthesized from most abundant biomass onion peel via double crucible method and it was explored as renewable carbon source for low-cost energy storage device. The supercapacitor electrode exhibits high specific capacitance of 127 Fg(-1) at the current density of 0.75 Ag-1 with capacitance retention of 109% after 2000 cycles in three-electrode system. More importantly, its symmetric supercapacitor device exhibits energy density of 13.61 Wh kg(-1) at the power density of 200.8 W kg(-1) with remarkable electrochemical stability revealing capacitance retention above 100% over 14000 cycles. Our study demonstrates that onion peel-derived carbon is suitable for future low-cost energy storage device.