Activated carbon derived from tree bark biomass with promising material properties for supercapacitors

Abstract

Activated carbon from tree bark (ACB) has been synthesized by a facile and environmentally friendly activation and carbonization process at different temperatures (600, 700 and 800 °C) using potassium hydroxide (KOH) pellets as an activation agent with different mass loading. The physicochemical and microstructural characteristics of the as-obtained material revealed interconnected microporous/mesoporous architecture with increasing trend in specific surface area (SSA) as carbonization temperatures rises. The SSA values of up to 1018 m2 g−1 and a high pore volume of 0.67 cm3 g−1 were obtained. The potential of the ACB material as suitable supercapacitor electrode was investigated in both a three and two-electrode configuration in different neutral aqueous electrolytes. The electrodes exhibited electric double-layer capacitor (EDLC) behaviour in all electrolytes with the Na2SO4 electrolyte working reversibly in both the negative (−0.80 V to −0.20 V) and positive (0.0 V to 0.6 V) operating potentials. A specific capacitance (Cs) of up to 191 F g−1 at a current density of 1 A g−1 was obtained for the optimized ACB electrode material in 1 M Na2SO4 electrolyte. A symmetric device fabricated exhibited specific Cs of 114 F g−1 at 0.3 A g−1 and excellent stability with a coulombic efficiency of a 100 % after 5000 constant charge–discharge cycles at 5.0 A g−1 and a low capacitance loss for a floating time of 70 h.