Structural Analysis of Furfural Resin-based Active Carbon to Control an Electric Double-layer Capacitor

Abstract

Active carbon was prepared by treating carburized furfural resin particles (1 µm in diameter) with potassium hydroxide solution for 0–0.5 h at 700–800°C in flowing nitrogen gas. The pore structure of the active carbon was then evaluated by nitrogen adsorption experiments. The active carbon particles (1 µm in diameter) prepared at 750°C-0 h or 800°C-0 h had ca. 2.5-fold greater mesopore volume and 1.9-fold greater mesopore ratio than those prepared at 700°C-0.5 h. The surface chemical structure was evaluated by X-ray photoelectron spectroscopy, while the fraction of organic functional groups in the pores was evaluated by Boehm titration. The carboxyl group fraction in the pores increased in the following order: 750°C-0 h (18.1%) ＜ 800°C-0 h (23.0%) ＜ 700°C-0.5 h (31.4%). The relationship between the pore size distribution, surface functional groups in the pores, and electric double-layer capacitor capacity was investigated for the specific surface area of 1200 ± 100 m2/g. The specific capacity increased in the following order: 700°C-0.5 h (66 F/g) ＜ 800°C-0 h (111 F/g) ＜ 750°C-0 h (148 F/g). This indicated that the amount of surface functional groups played a crucial role in the 6 M KOH electrolyte.

Keywords

• active carbon
• edlc
• furfural resin
• surface chemical structure