Electrochemical properties of an activated carbon xerogel monolith from resorcinol-formaldehyde for supercapacitor electrode applications

• Published in: RSC advances 2021-10, Vol.11 (53), p.33192-3321
• Main Authors: Huang, Minhu, Yoo, Seung Joon, Lee, Jae-Suk, Yoon, Tae-Ho
• Format: Article
• Language: English
• Subjects: Activated carbon; Aqueous solutions; Chemistry; Distilled water; Electrochemical analysis; Electrochemical impedance spectroscopy; Electrodes; Field emission microscopy; Formaldehyde; Heat treatment; Photoelectrons; Polycondensation reactions; Pore size; Pyrolysis; Raman spectroscopy; Soaking; Spectrum analysis; Thermogravimetric analysis; Weight gain measurement; Weight loss; X ray photoelectron spectroscopy; Xerogels
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/d1ra06462b

Activated carbon xerogel monoliths were prepared from resorcinol and formaldehyde via a catalyst-free and template-free hydrothermal polycondensation reaction, followed by pyrolysis and activation. The ratio of resorcinol (R) to distilled water (W) was varied to afford an interconnected pore structure with controlled pore size, while the pyrolysis temperature was optimized to give high specific surface area. Activation was carried out at 700 °C after soaking the samples in 6 M KOH aqueous solution. The same process, called "heat treatment", was also carried out without soaking in KOH for comparison. The weight loss upon pyrolysis, activation and heat treatment and the weight gain via KOH soaking were measured. Field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and an N 2 sorption instrument were utilized for characterization. Additionally, electrochemical properties were evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) with a 3-electrode system, while a 2-electrode system was also employed for selected samples. The highest specific capacitance of 323 F g −1 via GCD at 1 A g −1 was obtained at the R/W ratio of 45 and with 500 °C pyrolysis. In addition, this sample also exhibited 89.4% retention at 20 A g −1 in the current density variation and 100% retention in 5000 cycling tests. A monolithic carbon xerogel electrode for supercapacitors was prepared from resorcinol-formaldehyde, providing a specific capacitance of 323 F g −1 via GCD at 1 A g −1 and 100% retention upon 5000 cycling tests.