ON THE ACTIVATION-ENERGY OF THE ELECTROCHEMICAL REDUCTION OF O-2 ON PLATINUM

Data from the literature on activation parameters for the electrochemical reduction of O2 in various acid media (concentrated phosphoric acid, trifluoromethane sulphonic acid and perchloric acid) have been treated, using a model of stepwise change of the activation energy. It is shown that the increment of activation energy can be identified with the energy of a vibrational quantum corresponding to about 560 cm-1. Such wave numbers are characteristic for Pt-O stretching vibrations in platinum(II) complexes of oxygen ligands. It is thus suggested that the rate-determining step involves an activation of a Pt-O bond. When a sufficient number of vibrational quanta have been implanted in the stretching mode the reaction occurs.