Solid coin-like design activated carbon nanospheres derived from shallot peel precursor for boosting supercapacitor performance

Abstract

Thin porous carbon nanospheres based on natural materials, characterized by abundant availability, facile synthesis without templates, and heteroatom doping have confirmed the enhanced high performance of electrochemical energy storage devices. However, these potentials are difficult to obtain, and further poses a serious challenge. This work, activated carbon nanosphere was obtained from the biomass precursor shallot peel through a solid coin-like design with different chemical impregnations with high-temperature pyrolysis. The three different activators used were KOH, ZnCl2, and NaOH, selected to optimize the precursor's potential to produce porous carbon nanospheres. All the carbons prepared exhibited potential nano-sized morphological structures with a high carbon content of 77.71–90.11%. Furthermore, the oxygen content of 24.60% indicated a doping heteroatom for the electrode material. Surprisingly, the KOH impregnation exhibited a nanosphere-rich morphological structure with a diameter of 102–124 nm adhering to the nanofiber surface. This combination of material properties has the benefit of improving the supercapacitor's performance with a high specific capacitance of 170.12 F g−1 in a 1 M H2SO4 aqueous electrolyte. Meanwhile, the maximum specific energy reached 16.67 Wh kg−1 with a maximum specific power of 86.40 W kg−1 at a constant current density of 1.0 A g−1, in a two-electrode system. Therefore, the activated carbon with a solid coin-like design derived from shallot peel waste is a potential source of a rich nanospheres structure with a facile strategy for large-scale commercial electrochemical energy storage applications.