Abstract

Biochar derived from the pyrolysis of pine tannin is a green and available by-product of oil manufacturing that presents interesting features after having been activated by KOH at 650 degrees C. Different weight ratios of KOH to biochar were used and the resulting activated carbons (ACs) presented highly developed specific surface areas of up to 2190 m(2) g(-1), well-connected porosity and high oxygen content, leading to enhanced electrochemical performance when used as electrochemical capacitor electrodes in a 1 M H2SO4 aqueous electrolyte. Galvanostatic charge/discharge experiments evidenced that the best material achieved a maximum electrode capacitance of up to 232 F g(-1) (at 0.5 A g(-1)) with a capacitance retention of 70% at 10 A g(-1) using commercial mass loadings (i.e., approx. 10 mg cm(-2)). In addition, long cycling stability with a residual capacitance of 92 to 94% after 10,000 cycles at 5 A g(-1) was achieved. These results prove that ACs derived from pine tannin biochars have great potential for their commercial use as electrochemical energy storage devices. (C) 2021 Elsevier Inc. All rights reserved.