A novel method to tailor the porous structure of KOH-activated biochar and its application in capacitive deionization and energy storage.

By Amir M. Dehkhoda, E. Gyenge, N. Ellis. 2016

191 citations recorded by the source corpus.

Abstract This study reveals a novel method to tailor the micro- and meso-porous structures of activated biochar by exploiting the interaction between pre-carbonization drying conditions and carbonization temperature in KOH activation. Biochar samples were mixed with concentrated KOH and then dried under air or nitrogen for various periods of time (0–280 h) followed by carbonization at 475, 675 or 875 °C. It is confirmed that by manipulating drying conditions and carbonization temperatures, the KOH activated biochar can have a predominantly microporous, mesoporous or a combined (micro/meso) porous structure. The surface area, micropore and mesopore volumes tailored between: 488–2670 m2 g−1, 0.04–0.72 cm3 g−1, and 0.05–1.70 cm3 g−1, respectively. The mechanism of porosity development was investigated by FTIR analysis suggesting conversion of KOH to K2CO3 due to different drying conditions as a major role in tailoring the structure. The application of activated biochar with tailored porosity was investigated for Electric Double Layer adsorption of NaCl/NaOH to be employed in water treatment (capacitive deionization) or energy storage (supercapacitor) processes. The majorly microporous activated biochar (N2-dried activated at 675 °C) showed promising capacitances between 220 and 245 F g−1. Addition of mesoporous structure resulted in capacitances between 182 and 240 F g−1 with significantly reduced electrode resistance and improved capacitive behavior as evidenced by Impedance Spectroscopy and Galvanostatic Charge/Discharge tests.

Subfields: Biomedical Engineering, Electronic, Optical and Magnetic Materials, Water Science and Technology

View Paper: https://www.semanticscholar.org/paper/3a699c34dca3dc1e3f2418826f18796bf769d644