Self-foaming strategy to fabricate sunflower plate-derived porous carbon framework for high energy density supercapacitor

Herein, sunflower plate-derived nitrogen-doped porous carbon framework (SPPC) has been prepared by a one-step self-foaming and nitrogen doping strategy with sodium bicarbonate (NaHCO 3 ) as an activator and melamine as a nitrogen source. According to the self-foaming activation and abundant nitrogen doping effect produced by the thermal decomposition of NaHCO 3 and melamine, the typical SPPC-SM material exhibits a well-developed porous carbon skeleton structure, high specific surface area and high nitrogen content (8.35 wt%), which significantly enhances the electrochemical properties. The symmetrical supercapacitor constructed by the SPPC-SM and 0.5 M Na 2 SO 4 aqueous electrolyte has a wide and stable voltage window of 2 V, high energy density of 19.18 Wh kg −1 at a power density of 100.1 W kg −1 . In addition, the supercapacitor constructed by the SPPC-SM and ionic liquid (EMIMBF 4 ) electrolyte delivers ultra-wide operating voltage of 4 V and shows the high energy density of 74.04 Wh kg −1 at the power density of 400.1 W kg −1 , as well as a superior stability with capacitance retention of 87.1 % after 30,000 cycles. The green preparation of biomass-based nitrogen-doped porous carbon frameworks presented in this work provides a promising strategy for realizing wide operating voltage and high energy density supercapacitors. • Bread-inspired self-foaming strategy is used to fabricate porous carbon framework • Sodium bicarbonate is employed as dual functions carbonization assisted medium. • SPPC demonstrates a 3D honeycomb-like carbon framework structure. • Supercapacitor based on SPPC carries ultrahigh output voltage and high energy density.