Electrocatalysis of O2 Reduction at Glassy Carbon Electrodes Modified with Adsorbed 1,4-Dihydroxy-9,10-anthraquinone Derivatives

The preparation and electrochemical characterization of glassy carbon electrodes modified by four recently synthesized 1,4-dihydroxy-9,10-anthraquinone derivatives are reported. The anthraquinones used were strongly and irreversibly adsorbed on the preanodized glassy carbon electrodes. The electrochemical behavior and stability of the modified electrodes were studied by cyclic voltammetry at different acidic and basic aqueous solutions, and pH of 6—7 was chosen as the optimum working pH. The adsorbed anthraquinone derivatives showed excellent electrocatalytic ability for the reduction of O2 to H2O2 with overpotentials of from 560 to 650 mV lower than that of a plain glassy carbon electrode. The heterogeneous rate constants for the reduction of O2 at the surface of the modified electrodes were determined by rotating-disk electrode voltammetry using the Koutecky–Levich plots. The apparent diffusion coefficient of O2 in buffered aqueous O2-saturated solutions was also estimated.