Electrochemical performance of diazonium-generated carbon films for electrochemical double-layer capacitors (EDLCs)

Carbon-based electrode materials for energy storage systems have received considerable attention thanks to their excellent mechanical properties, large specific surface areas and moderate electrical conductivities. Here, diazonium-generated carbon films on the flexible carbon paper (CP) electrodes were prepared through electrochemical reduction of aryl diazonium salts bearing COOH, NO2, CH3 and H functional groups. The production of polymeric carbon films by diazonium modification method was preferred because it is a simple and effective process, and also the carbon-based films prepared by this method are covalently attached to the carbon electrode surfaces. The capacitive properties of the robust carbon films were assessed by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) in three-electrode and asymmetric device configurations. The results indicated that diazonium-generated carbon films on flexible substrates exhibited typical EDLC behavior with high specific capacitance values (237.6–446.9 F g−1 at 0.5 A g−1 current density), and also their capacitive performances were largely dependent upon the functional groups on the benzene ring. Overall, this work reveals that the diazonium modification method is a promising approach to create the carbon-based active electrode materials in advanced energy-storage systems.