GAS-PHASE ELECTROREDUCTION OF O2 ON GOLD NAFION AND (UNDERPOTENTIAL EPOSITION, GOLD) NAFION(R) ELECTRODES

The electroreduction of oxygen was examined on a gold-solid polymer electrolyte (SPE) electrode prepared by electroless deposition of gold onto one side of a Nafion(R) membrane. The gold side was in contact with the gaseous phase and the free side was in contact with an electrolytic solution (NaOH or HClO4). Oxygen reduction on Au-Nafion electrodes shows the same mechanism as on a conventional gold electrode, i.e O2 + e- --> O2- is the rate-determining step. The reaction order with respect to O2 is fractional and this is ascribed to a slow removal of the reaction products from the active sites. Au-Nafion electrodes modified by underpotential deposited (UPD) lead and bismuth show an enhanced activity of O2 and H2O2 reduction, as found in conventional solution phase studies. From the behaviour of UPD modified electrodes it was also concluded that the charge transfer reaction occurs at the interior of the metal layer, in contact with the Nafion membrane.