The electrochemical reduction of oxygen has been studied on quinone-modified glassy carbon (GC) electrodes as a function of solution pH using the rotating disk electrode (RDE) technique. The surface of GC was grafted with anthraquinone (AQ) and phenanthrenequinone (PQ) by electrochemical reduction of their diazonium derivatives and the oxygen reduction measurements were carried out at different pHs (pH 7-14). The redox-potentials of surface-bound quinones were determined using cyclic voltammetry (CV). The kinetic parameters of oxygen reduction on GC/AQ and GC/PQ electrodes were determined considering a surface redox catalytic cycle model for quinone-moditied electrodes. (c) 2007 Elsevier Ltd. All rights reserved.