Cassava peel derived self-doped and hierarchical porous carbon as an optimized electrode for the ultra-high energy density of supercapacitor

The development of advanced electrode materials with optimized properties, including structural morphology, high porosity, and functional group doping, is very important to enhance the energy density of solid-state supercapacitors. Here, a hierarchical 3D porous carbon self-doping obtained from cassava peel through an environmentally benign approach to optimize the supercapacitor working electrode material. The unique sponge-like interconnected pore structure and self-doping features are controlled through chemical impregnation (CIP) of ZnCl2 (CIP/Z), KOH (CIP/K), and H3PO4 (CIP/H) and high-temperature pyrolysis in an N2&CO2 gaseous environment. Furthermore, the optimized CIP/Z carbon material exhibits high content of 94.606 % and a self -doping oxygen heteroatom of about 2.672 %. The unique sponge-like morphology possessed enriches micro -pores of 94 %, indicating high performance as an electrode material. The electrochemical properties were assessed through a symmetric supercapacitor system assembled in a solid free-binding coin yielding an excellent specific capacitance of 257 F g-1 at 1 A g-1. Meanwhile, the optimized electrode has a high rate capability of 92.43 % and maintained a coulombic efficiency of up to 91.10 % at 10 A g-1. The best working efficiency supercapacitor cell can show a jump in energy density of 35.69 Wh kg-1 at a specific power of 167.68 W kg-1 in an aqueous electrolyte of 1 M H2SO4. These excellent results provide important insights for optimizing electrode materials derived from cassava peel-based porous carbon for symmetrically designed supercapacitors of binder -free solid coins in aqueous electrolytes with high energy density.