Facile fabrication of N-self-doped porous carbons from green solid waste for supercapacitors with high cycling stability and flexibility

Abstract

Carbon has become a commercial electrode material for supercapacitors. From the viewpoint of sustainable development, biochar is a superior electrode material for supercapacitors. Therefore, the synthesis of supercapacitor layered interconnected porous carbon materials with excellent electrochemical performance from biomass solid wastes has become a research hotspot. This paper reports the preparation of sunflower straw-based porous carbon (SSPC) materials with good pore size distribution, self-doped nitrogen and oxygen, and microporous/mesoporous structure using HCOOK as a new-type activator. In the three-electrode system, the capacitance of the optimal sample SSPC600-4 was maintained at 230 F g −1 under a high current density of 100 A g −1 . The symmetrical supercapacitor had the highest energy density of 25 Wh kg −1 (500 W kg −1 ) and excellent cycle stability (96.21% capacity after 20000 cycles). In addition, the all-solid-state symmetrical supercapacitors showed flexibility and successfully powered five 3 V bulbs when connected in series, thus confirming their potential applications in portable and wearable devices. Using waste sunflower straw as raw material, potassium formate (HCOOK) as a new non-toxic activator, nitrogen and oxygen self-doped layered porous carbon material was prepared by one-step activation carbonization method. The electrochemical measurements demonstrate that nitrogen and oxygen self-doped layered porous carbon material have excellent electrochemical performance for supercapacitor. • High-performance nitrogen and oxygen self-doped porous activated carbon are prepared with sunflower straw as precursor and potassium formate (HCOOK) as a new non-toxic activator. • Excellent electrochemical properties of nitrogen and oxygen self-doped porous activated carbon are achieved with optimum specific capacitance of 346 F g -1 at the current density of 1 A g -1 . • At 1 A g -1 , the high energy density of up to 25 Wh kg -1 is delivered at the power density 500 W kg -1 • The all-solid-state symmetrical supercapacitors device shows high flexibility and high energy density.