Abstract:
Activated carbon (ACB) obtained from tree bark waste biomass was obtained by adopting an optimized
activation and carbonization route using potassium hydroxide (KOH) pellets. The morphological and
structural characteristics of the optimized carbon material revealed a porous network suitable for charge
storage. The potential of the ACB material as a suitable supercapacitor electrode was investigated in
a symmetric two electrode cell configuration using a polymer-gel/KOH active electrolyte. The KOH was
included to improve ionic mobility within the polyvinyl alcohol (PVA) gel, while carbon acetylene black
and a polymer-fullerene blend acted as the conductive additives. The cell exhibited an EDLC behaviour
in all electrolytes with the PVA/KOH/carbon black (PKCB) electrolyte portraying the best electrochemical
response with a 1.4 V voltage window. A specific capacitance (CSP) of 227 F g 1 was obtained with
a corresponding energy density of 15.5 W h kg 1 and power density of 700 W kg 1 at a current density
of 0.5 A g 1. An excellent stability was exhibited with a coulombic efficiency of 98% after 5000
continuous cycles at 5.0 A g 1 and a slight deterioration of the ideal electrochemical behavior was
observed after further subjecting the electrode to a floating test for 120 h (5 days) at 1.4 V. Interestingly,
the gel-based electrolyte showed a peculiar “recuperating behavior” after further floating process and
negligible charge loss after a self-discharge process for 30 h at 1.0 A g 1 which demonstrates the
viability for adopting gel-electrolytes in SC devices from plant biomass waste.
