A study on optimal pore development of modified commercial activated carbons for electrode materials of supercapacitors

Highlights: • The specific capacitance of commercial activated carbons in EDLCs were dramatically enhanced (18% up) by our method. • Activated carbon showed enhanced specific surface area from 1690 to 2290 m²/g after the post activation method. • The samples containing high mesopores fraction showed better specific capacitance at similar specific surface area. - Abstract: This study aimed to understand the impact of CO₂ activation of commercial activated carbons (AC) on the changes in pore characteristics and the electrochemical property. The surface structure of manufactured AC was observed with a X-ray diffraction (XRD); the pore characteristics were analyzed at N₂/77 K isothermal absorption using the Brunauer-Emmett-Teller (BET) and Dubinin-Radushkevich (DR) equations. In addition, the electrochemical characteristics were analyzed by means of an electrolyte of 1 M (C₂H₅)₄NBF₄/propylene carbonate, using a charge/discharge test, cyclic voltammetry (CV), and impedance. The N_2/77 K isothermal absorption curve of the manufactured AC falls under Type I in the classification of the International Union of Pure and Applied Chemistry (IUPAC) and was found to largely comprise micropores. The specific surface area increased from 1690 m²/g to 2290 m²/g, and the pore volume grew from 0.80 cm³/g to 1.10 cm³/g. The analysis of electrochemical characteristics also found that the specific capacity increased from 17 F/g to 20 F/g (in a full cell condition). Based on these results, we were able to determine the pore characteristics of commercial AC through an additional activation process, which consequently allowed us to manufacture the AC with an advanced electrochemical property.