Effects of electrolytes and electrochemical pretreatments on the capacitive characteristics of activated carbon fabrics for supercapacitors

Abstract

The capacitive characteristics of activated carbon fabrics (ACFs) coated on the graphite substrates were systematically investigated by means of cyclic voltammetry and the galvanostatic charge–discharge technique. Effects of the PVDF contents in the electronically conductive binder, electrochemical pretreatments, and the electrolytes on the capacitive performance of ACFs were compared in aqueous media. These ACF-pasted electrodes showed the more ideally capacitive responses in 1 M NaNO3 with a specific capacitance of 76 F g−1 when the electronically conductive binder contained 40 wt.% PVDF. The specific capacitance of ACF-pasted electrodes reached a maximum in 0.5 M H2SO4 (about 153 F g−1 measured at 25 mV s−1), due to the presence of a suitable density of oxygen-containing functional groups, when they were subjected to the potentiostatic polarization at 1.8 V (versus reversible hydrogen electrode (RHE)) or potentio-dynamic polarization between 1.3 and 1.8 V in NaNO3 for 20 min. The oxygen-containing functional groups within the electrochemically pretreated ACFs were identified by means of X-ray photoelectron spectroscopy (XPS).