Behavior of activated carbon cloths used as electrode in electrochemical processes

Abstract

The effects of polarization on the nanotexture and the surface chemistry of an activated carbon cloth were investigated. Electrochemical modification was performed in a sodium sulfate electrolyte, by applying negative current or increasing positive potentials. The porous structures of the polarized samples were analyzed by N2 and CO2 adsorption. Surface chemistry properties such as the nature and the amount of functional groups were studied through various characterization techniques. Additionally, the electrochemical properties of the modified samples were investigated using cyclic voltammetry. It is shown that anodic polarization leads to a significant oxidation of the pristine carbon material, characterized by the substantial incorporation of a wide variety of oxygenated groups and a significant modification of the porous network. A capacitance increase is highlighted for the anodically polarized samples and can be attributed to the incorporation of CO-type surface groups. While cathodic polarization leads to a slight modification in surface chemistry and nanotexture, anodic treatment causes noticeable transformations of the pristine carbon material. Additionally, the oxidation phenomenon which occurs at the carbon electrode appears to be quite different in the two modes. A comparative study with a second carbon material, possessing a different surface chemistry and porous characteristics, was also carried out.