Activated carbons effectively purified by post-heat treatment under vacuum conditions

• Published in: Carbon Letters Vol. 31; no. 5; pp. 973 - 984
• Main Authors: Kim, Junam, T. Nguyen, Hoai Van, Bahk, Gyung Jin, Kwak, Kyungwon, Lee, Kyung-Koo
• Format: Journal Article
• Language: English
• Published: Incheon Springer Nature B.V 01-10-2021
• Subjects: Activated carbon; Adsorption; Atmospheric pressure; Capacitance; Carbon; Electrochemical analysis; Electrochemistry; Electrodes; Electrolytes; Fourier transforms; Functional groups; Heat treating; Heat treatment; Heat treatments; Infrared spectroscopy; Nitrogen; Photoelectron spectroscopy; Photoelectrons; Pore size; Raman spectroscopy; Surface area; Telecommunications systems; Temperature; Vacuum; X ray photoelectron spectroscopy; X-ray diffraction; Japan
• ISSN: 1976-4251; 2233-4998
• DOI: 10.1007/s42823-020-00209-y

The effect of heat treatment and vacuum conditions on the textural properties and electrochemical performance of commercially available activated carbons (ACs) was investigated. The AC after post-heat treatment was characterized by nitrogen adsorption–desorption, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy measurements. The ACs treated under vacuum conditions exhibit a higher specific surface area and micropore surface area than those treated under nitrogen atmospheric pressure without significantly affecting the graphite structure of the AC. Under 800 °C temperature and vacuum conditions (AC-V800), the AC with the highest Brunauer–Emmett–Teller surface area of 1951.9 m2 g−1 (16.4% improvement relative to that of the original AC (1677.2 m2 g−1)) was obtained. This is attributed to the removal of oxygen-containing functional groups and volatile matters in the carbon by thermal treatment under vacuum conditions. Consequently, the electric double-layer capacitor using ACs treated under vacuum conditions (1 kPa) at 800 °C (AC-V800) shows considerably improved electrochemical performance in terms of higher specific capacitance and better cycling stability at a high working voltage (3.1 V), compared to the nitrogen-treated and commercial ACs.