VOLTAMMETRIC STUDIES OF ELECTROCHEMICAL PRETREATMENT OF ROTATING-DISCGLASSY-CARBON ELECTRODES IN PHOSPHATE BUFFER

Cyclic voltammetry was used to study the formation of graphite oxide f ilm on the surface of rotating-disc glassy carbon electrodes. The film was formed by continuous potential cycling in phosphate buffer electr olyte. It was found that when cycling between the totally oxidized and totally reduced potential ranges (between +2.3 and -1.2 V vs. SCE), w ell-shaped redox peaks were obtained. Typical voltammograms comprised one cathodic and two anodic waves, where the anodic waves were directl y related to the oxidation of surface-bound products associated with t he cathodic process. All three processes were pH dependent. Freshly fo rmed surface graphite oxide films were not stable and would undergo tr ansformation to give the stable state upon potential cycling between p otentials +/-1.0 V. The ultimate stable voltammograms were characteriz ed by two electrode processes. The quasi-reversible process involved s urface quinone-like functional groups, while the other irreversible pr ocess might be related to the uptake and release of hydrogen ions at t he porous graphite oxide film.