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The preparation and electrochemical characterization of glassy carbon electrodes modi®ed by some recently synthesized anthraquinone substituted podands were investigated. These compounds were found to be strongly and irreversibly adsorbed on the preanodized glassy carbon electrodes. The electrochemical behavior and stability of the modi®ed electrodes were studied by cyclic voltammetry in acidic aqueous solutions. The in¯uence of pH on the electrochemical behavior of the electrodes was studied and a pH of 4.5 was chosen as the optimum working pH. The ability of the modi®ed electrodes as potential electrocatalysts for the reduction of dioxygen to hydrogen peroxide was tested by cyclic voltammetry, chronomperometry and rotating disk electrode voltammetry. They showed excellent electrocatalytic ability for the reduction of O 2 at pH 4.5 with overpotentials ranging from 380 to 470 mV lower than the plain glassy carbon electrode. The heterogeneous rate constants for the reduction of O 2 at the surface of these modi®ed electrodes were determined by the use of KouteckyLevich plots. In addition, the apparent diffusion coef®cients of O 2 in buffered aqueous O 2 -saturated solution was estimated.

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Electrocatalytic oxidation of methanol on a glassy carbon disc electrode modified with Ni(II)-hematoporphyrin IX, complex and conditioned by potential recycling in a limited range (between 100 and 600 mV vs. SCE) in 0.10 M NaOH solution, abbreviated as NiOHPME(A), was studied by cyclic voltammetry in alkaline medium. The results were compared with those obtained for a NiO modified glassy carbon electrode, NiOME, prepared in similar conditions. The findings show that the NiOHP film at NiOHPME(A) behaves as an efficient electrocatalyst for the oxidation of methanol in alkaline medium via Ni(III) species with the cross-exchange reaction occurring throughout the layer at a low concentration of methanol and for a thin film of modifier. A plausible mechanism was proposed for catalytic oxidation of methanol at NiOHP modified electrode. Moreover, the effects of various parameters such as the scan rate, methanol concentration, thickness of NiOHP film and the real surface area of modified electrode on the oxidation of methanol were investigated. Finally, it has been shown that the NiOHPME(A) has a long-term stability toward the oxidation of methanol.

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