Surface engineered carbon-cloth with broadening voltage window for boosted energy density aqueous supercapacitors

An efficient strategy of surface engineering is developed to extraordinarily boost the energy density of multiscale porous carbon cloth for aqueous symmetric supercapacitors by optimizing the oxygen-containing functional groups. The operating voltage with neutral electrolyte is remarkably broadened from 1.3 to 1.8 V for electrochemical oxidized active carbon cloth (EOACC), enabling its ultrahigh areal capacitance (1548 mF cm(-2)) and extraordinary energy density (239.25 mu Wh cm(-2)). More importantly, engineering such a functionalized electrode with improved operating potential window is critically hinged on the fundamental understanding of the underlying electrochemical mechanism. The outstanding performance can be attributed to the enlarged ions-accessible specific surface area and created electrochemical active C=O quinone-type groups, contributing to the combination of electrical double-layer capacitance and pseudo-capacitance, respectively. More significantly, the broadened potential window is originated from the increase of the onset overpotential for oxygen evolution reaction, induced by the physical barrier of adsorbed Na+ and the kinetic limitations of fast faradic redox reactions. This strategy sheds a light on the understanding of the electrochemical mechanism for broadened potential range, which provides a promising way for designing and engineering carbon-based aqueous supercapacitors with boosted energy density. (c) 2020 Elsevier Ltd. All rights reserved.