Peanut shell waste derived porous carbon for high-performance supercapacitors

Low-cost and high-performance porous carbon electrode materials are the key to supercapacitors. Here, we reported the preparation of porous carbon materials by high-temperature carbonization coupled with chemical activators (H3PO4, ZnCl2, KOH) using peanut shell waste. The as-synthesized porous carbon with KOH as the chemical activator (KOH-AC) has the best ideal electric double-layer capacitance performance, outperforming other activator-treated porous carbon. In the three-electrode system, the prepared KOH-AC electrode material showed an ultra-high specific capacitance of 575.7 F g−1 at a current density of 0.5 A g−1, good rate characteristics and excellent electrochemical stability (106.5 % initial capacitance after 10,000 cycles), which exceeded that of most biomass carbon-based materials. In the two-electrode system with 6 M KOH as electrolyte, the symmetrical supercapacitor based on KOH-AC showed a high specific capacitance of 390.9 F g−1 at 0.5 A g−1 current density in the voltage rang of 0–1.3 V, with the maximum energy density of 22.2 Wh kg−1 and power density of 319.97 W kg−1 and excellent cycle stability (93.8 % after 10,000 cycles). In addition, it is also studied that all-solid-state flexible symmetric supercapacitor in PVA/KOH electrolyte shows a high specific capacitance of 432.7 F g−1 at 0.5 A g−1 current density and can provide energy density of 18.2 Wh kg−1 and power density of 275.3 W kg−1. In summary, this work synthesized high-performance porous carbon materials from renewable and sustainable biological wastes, which provided a feasible method for the application of biomass carbon in energy storage.