Electrochemical activation of conductive carbon cloth for high-performance negative electrode in supercapacitor

Carbon cloth (CC) has emerged as a popular substrate for flexible electronic devices and can also be functionalized with pseudocapacitive groups to serve as the negative electrode in supercapacitors. In this work, the areal capacitance of the conductive CC substrate is significantly enhanced through electrochemical oxidation. The oxidation conditions are optimized to modify the content of surface oxygen-containing functional groups. X-ray photoelectron spectroscopy (XPS) results indicate that the formation of these oxygen-containing surface functional groups is highly dependent on the water content of the electrolyte solution, the number of effectively ionized sulfate ions, and the concentration of nitric acid. Furthermore, the ratio of pseudocapacitive groups exhibits a linear relationship with areal capacitance at low current densities. The optimized activated carbon cloth (ACC) electrode demonstrates an impressive areal capacitance of 1.9 and 1.2 F cm-2 at 2 mA cm-2 in KOH and Na2SO4 solutions, respectively, showcasing superior rate performance and cyclic stability. High-mass-loading asymmetric supercapacitors utilizing ACC as the negative electrode can operate under pH-universal conditions, delivering high capacitance, notable energy densities, and excellent cycling stability.