Surface Modification of Carbon Fiber by using Electro-oxidation and -reduction Sequential Procedure

Abstract

A new method for the surface modification of carbon fiber by using electro-oxidation and -reduction sequential procedure has been exploited. The introduction of hydroxyl groups on carbon fiber was attained by the electrooxidation of the NO₃ anion containing electrolyte using the carbon fiber as an anode, and the anodically introduced hydroxyl groups were successively transferred to the alkoxy groups by the electroreduction in the presence of alkyl halides using the oxidized carbon fiber as a cathode. The functional groups introduced on the carbon fiber were estimated by the X-ray photoelectron spectroscopy, the observation of the hydrophilicity of the carbon fibers, and also by using the carbon fibers as cathodes for the electroreduction of acetophenone (1). The diastereoselectivity of the reduced product, 2,3-diphenyl-2,3-butanediol (2), in the electroreduction of 1 indicated the interaction between the electrogenerated radical anion species of 1 with the hydroxyl groups on the carbon fiber surface, and the dl/meso ratio was found to increase with an increase in the content of the hydroxyl groups on the carbon fibers. The sequential modification method for carbon fibers in one-pot was successfully performed by using the MeCN–H₂O (3:1) mixed solvent containing the mixed supporting electrolytes Bu₄NNO₃–Bu₄NClO₄ (1:1) and alternating the polarity of the electrodes to give the carbon fibers having high content of hydroxyl or alkoxy groups.