Double Layer Properties of Spent Coffee Grounds-derived Carbon Activated with Potassium Hydroxide (KOH)

• Published in: Denki kagaku oyobi kōgyō butsuri kagaku 2013/10/05, Vol.81(10), pp.828-832
• Main Authors: KIKUCHI, Keisuke, YASUE, Tomohiro, YAMASHITA, Rie, SAKURAGAWA, Satoshi, SUDOH, Masao, ITAGAKI, Masayuki
• Format: Article
• Language: English
• Subjects: Activated Carbon; Coffee Grounds; EDLC; KOH Activation
• ISSN: 1344-3542; 2186-2451
• DOI: 10.5796/electrochemistry.81.828

Large amounts of spent coffee grounds (SCGs) are generated all over the world. Since SCGs contain a lot of carbon and inherently has a porous structure, SCGs are considered to be a valuable industrial resource by carbonization. According to our previous research, it was apparent that the specific surface area of SCGs-derived carbon was greatly improved by potassium hydroxide (KOH) activation. In this research, we prepared an electric double layer capacitor (EDLC) using SCGs-derived carbon activated with KOH, and compared them to phenol resin-derived activated carbon (MSP-20, Kansai Coke and Chemicals Co., Ltd.), which is commonly used as a reference material in EDLC research. Electrodes were prepared by mixing 80 wt% activated carbon, 10 wt% carbon black and 10 wt% polytetrafluoroethylene (PTFE) and the electrolyte used was 1 M triethylmethylammonium-tetrafluoroborate (TEMA-BF4)/propylene carbonate (PC). The capacitive performance was evaluated by a constant current charge-discharge cycle measured with various electrical current loads from 5 to 150 mA/cm2. Although the capacitance of SCGs-derived carbon activated with KOH was inferior to that of MSP-20 at low current load density, it had high capacitance in high rate charge-discharge cycles. This suggests that the EDLC consisting of SCGs-derived activated carbon electrodes is superior to MSP-20 in capacitance retention rate when used at a high electric current density.