Effect of oxygen-containing functional groups on the impedance behavior of activated carbon-based electric double-layer capacitors

The surface chemistry of activated carbon was treated with sulfuric acid and hydrogen to analyze the oxygen-containing functional groups on the impedance behavior of electric double-layer capacitors. Based on the electrochemical impedance spectrum (EIS), an equivalent circuit model was proposed considering the kinetic and charge transfer characteristics, and Marquardt fit procedure was applied to the EIS data. The simulated results indicate that the oxidation treatment made the ionic resistance within the pore of carbon electrode decrease, and the ion diffusion coefficients significantly increase, which leads to improvement of power capability of the carbon electrode.