Ultrasonic-assisted chemical synthesis of activated carbon from low-quality subbituminous coal and its preliminary evaluation towards supercapacitor applications

Abstract

An eco-friendly method consisting of ultrasonic-assisted chemical activation to synthesize the activated carbon (AC) with high specific surface area and high porosity from the low-quality subbituminous Indian coals is reported in this paper. There is a lack of studies on ultrasonic-assisted chemically synthesized ACs from precursor materials like coal. In this study, the adsorption properties, energy density, and power density of the ACs were improved by application of low-energy (40 kHz) ultrasonic irradiation via formation of high surface area and surface porosity. Physico-chemical properties, specific surface area (SSA), surface morphology, identification of surface functional groups, and other structural studies of synthesized activated carbon were evaluated by using proximate and ultimate analysis, Brunauer-–Emmett–Teller (BET) analysis, Field emission-scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Powder X-ray diffraction (XRD), and Raman spectroscopy, respectively. The maximum specific surface area (SSA) and total pore volume (VTotal) of the coal-derived activated carbon are 789.910 m2/g and 0.103cc/g, respectively. The preliminary electrochemical evaluation the coal-derived ACs showed reasonably good electrochemical properties with a maximum potential window of 2.5 V and more than 1000 cycles with considerable energy density and power density with the possibility of making low-cost supercapacitors for use in small/general electronics. In addition, the reported ultrasonic-assisted chemical activation method is observed to be more effective than other activation methods to synthesize the ACs from abundant coal resources on a large-scale.