RANDOMLY ORIENTED GRAPHITE ELECTRODE .1. EFFECT OF ELECTROCHEMICAL PRETREATMENT ON THE ELECTROCHEMICAL-BEHAVIOR AND CHEMICAL-COMPOSITION OFTHE ELECTRODE

Randomly oriented graphite electrodes from Union Carbide (ATJ) and Sta ckpole (SP2020) have been characterized by classical acid-base titrati on, weight measurements, cyclic voltammetry and X-ray photoelectron sp ectroscopy (XPS) before and after various chemical and electrochemical pretreatments, It was found that the concentration of strong and weak acidic groups increases upon electrochemical oxidation of the graphit e electrode. The weight increase of a graphite electrode as a result o f electrochemical oxidation is attributed to the formation of oxidized graphite and the intercalation of anions and solvent molecules into t he graphitic material. The intercalation of sulfate was confirmed by t he increase of the sulfur 2s and sulfur 2p peaks of the XPS spectra. T he electrochemical oxidative pretreatment also causes an increase of t he capacitive envelope of the cyclic voltammogram which is not solely related to an increase of the surface area of the electrode. A set of well-defined anodic and cathodic peaks centered at 0.38 V vs. SCE also develops upon oxidation and is attributed to the presence of quinone/ hydroquinone redox species.