Biowaste derived porous carbon sponge for high performance supercapacitors

Here, an agricultural waste (the stem pith of helianthus annuus, SPHA) is firstly used as the precursor for preparing three-dimensional (3D) porous carbon sponge (PCS). The as-prepared 3D PCS (SPHA-700) possesses unique sponge-like structure, large specific surface area (SSA) and high nitrogen doping level (4.52 at.%), which benefit the enhancement of conductivity (5.8 S cm(-1)) and wettability. As a binder-free electrode for solid-state symmetric supercapacitor, SPHA-700 delivers a relatively high specific capacitance of 137.1 F g(-1) at 0.5 A g(-1). Moreover, activated SPHA-700 (SPHA-ac-700-2) displays an even higher specific capacitance (403.6 F g(-1) at 0.5 A g(-1)) in 6.0 M KOH electrolyte. The SPHA-ac-700-2-based symmetrical supercapacitor can offer high specific capacitance (271 F g(-1) at 1 A g(-1)) and good rate capability (82.1% of capacitance retention at 1-80 A g(-1)) in 6.0 M KOH electrolyte, together with high energy density (23.3 Wh kg(-1) at 450 W kg(-1)) in 1.0 M Na2SO4 electrolyte. Such excellent performance of SPHA-ac-7002 is believed to have originated from the crushed sponge-like structure, O/N-co-doping (10.6 at.% O and 3.3 at.% N), high SSA, large total pore volume, and hierarchical pore structure. (C) 2021 Published by Elsevier Ltd on behalf of Chinese Society for Metals.

Automated summary

Utilizing stem pith of helianthus annuus as precursor, a three-dimensional porous carbon sponge with unique structure and high performance was prepared for application in supercapacitors, demonstrating high specific capacitance and stability.