Abstract
Mesoporous carbon nanospheres are produced from biowaste,
Allium cepa
peels, well known as “onion” dry peels using the catalyst-free pyrolysis method. The synthesis process involves an unusable bio-precursor that is accumulated in millions of tons per year. The obtained materials show nanosphere morphology with particles size of 63–66 nm and surface area up to 2962 m
2
g
−1
. After pyrolysis at 800, 900, and 1000 °C, the carbon nanospheres are directly applied for supercapacitance study without further activation processes. The electrochemical studies show promising results such as high electrode capacitance of 189.4 at 0.1 A g
−1
in 3 M KOH. Moreover, full cell symmetrical supercapacitor is fabricated and further investigated under a wide potential window up to 1.6 V. An excellent electrochemical behavior is observed for the supercapacitor in terms of high energy density of 22.1 Wh kg
−1
at a power density of 39.6 W kg
−1
, high cyclic stability of 78%, and high coulombic efficiency of 90% over 4500 cycles at 0.5 A g
−1
. These studies support carbon nanospheres obtained from
Allium cepa
wastes to be used as promising materials for supercapacitor application.
Graphical abstract