Oxygen reduction on Nafion-coated thin-film palladium electrodes

The electrochemical reduction of oxygen on thin Pd films with a nominal thickness of 0.25-10 nm was studied in alkaline and acidic solution using the rotating disk electrode (RDE) method. The Pd films on glassy carbon electrodes were prepared by electron beam evaporation and coated with a Nafion layer. The surface morphology of the films was examined by transmission electron microscopy (TEM). In 0.1 M KOH the electrocatalytic activity of Pd electrodes towards oxygen reduction was high and the specific activity (SA) did not depend on the film thickness. In 0.05 M H2SO4 the activity was lower and a decrease of SA with decreasing film thickness was observed. The oxygen reduction reaction on thin Pd films predominantly followed a four-electron pathway in both solutions and the reduction mechanism was similar to that on bulk Pd, the first electron transfer being the rate-limiting step. (C) 2010 Elsevier B.V. All rights reserved.