Electroreduction of dioxygen on polycrystalline platinum in alkaline solution - I. Platinum surface pretreated by potential cycling between 40 and 1450 mV

The first part of a study of the electroreduction of dioxygen on different polycrystalline platinum surfaces in 1 M NaOH is reported. The results pres ented refer to a platinum surface that was pretreated by cycling the applie d potential between 40 and 1450 mV. The rotating ring-disk electrode polari zation curves for the reduction of O-2 show hysteresis, which is observed w ithin the entire potential range explored (40 to 1450 mV), increases as the rotation rate increases, is specially large above 300 mV and significantly decreases when the disk is coated with a Nafion film, mainly as a result o f the increase of the current intensity in the anodic scan (which is especi ally observed within the 300-700 mV potential range and indicates significa nt HO2- disproportionation in this range). These polarization curves entire ly follow those recorded for the reduction of HO2- both in the cathodic and in the anodic scan, clearly showing that the reduction of O-2 on this plat inum surface is completely dependent on how the surface deals with the HO2- formed during the O-2 reduction process. The details of the polarization c urves are discussed in relation to the details of the surface electrochemis try revealed by the correspondent cyclic voltammogram. (C) 2000 The Electro chemical Society. S0013-4651(99)12-102-5. All rights reserved.