Surface redox catalysis for O2 reduction on quinone-modified glassy carbon electrodes

The electrochemical reduction of oxygen on bare glassy carbon (GC) and on electrodes grafted with anthraquinone has been studied using the rotating ring-disk electrode (RRDE) technique. The electrode surface was grafted by the electrochemical reduction of the corresponding diazonium salt. The functionalised electrode showed quasi-reversible redox behaviour in oxygen-free 0.1 M KOH and the cyclic voltammetric response of the surface bound anthraquinone was stable on potential cycling. The covalently attached anthraquinone acts as an electrocatalyst for oxygen reduction and a well defined diffusion limited current plateau was observed in the potential range from −0.75 to −1.25 V (SCE) in 0.1 M KOH. The RRDE results show that oxygen reduction on both electrode surfaces studied stops at the hydrogen peroxide stage. The modified carbon electrodes are potential candidates for the electrochemical production of hydrogen peroxide.