Low metal content and hierarchically porous structure of “Fabaceae-Plants” derived activated carbon for high-performance supercapacitors

Plants with naturally ordered tissues and unique cell structures have become good precursors as activated carbon (AC) electrodes for supercapacitors. The various inherent plants derived ergastic substances induce numerous impurities in ACs, seriously impeding electrochemical performance. Aiming at elevating electrochemical activities, we herein, select suitable “Fabaceae-Plants” precursors via pre-leaching and carbonization-KOH activation for purer AC supercapacitor electrodes. The inherent parenchyma tissues and intrinsic low metal ion properties ensure “Fabaceae-Plants” derived ACs have large specific surface areas (SSA) (> 3000 m2 g−1) and low self-discharge rates. After ethanol reflux, most ergastic substances were removed, leading to a lower metal ion content that meets the standard procedure in Chinese GB/T 37386-2019 codes and higher mesopore volumes due to the better KOH activation effect. The mung bean sprouts-based activated carbon (AC) prepared by ethanol reflux exhibits higher capacitance (370 F g−1 at 0.5 A g−1), excellent rate performance (81.8 % from 0.5 to 50 A g−1), and an impressively low open circuit voltage attenuation rate (19.9 mV h−1). These characteristics are attributed to the synergistic effect of low metal ion impurities and higher mesopore volumes. Hence, the “Fabaceae-Plants” derived ACs are potential materials for clean energy storage and conversion systems, and the pre-leaching strategy may propose a strategy for high value-added utilization of biomass. [Display omitted] •“Fabaceae-Plants” are purer activated carbon electrode precursors for less ergastic substances.•Activated carbon electrodes are prepared via pre-extraction and carbonization-KOH activation.•The metal ions content of the purer activated carbons can meet the standard procedure of Chinese GB/T 37386-2019 codes.•Removing ergastic substances by ethanol reflux suppressed the self-discharge and enhanced electrochemical performances.