Electroreduction of oxygen on Nafion®-coated thin platinum films in acid media

Electrocatalytic oxygen reduction reaction (ORR) kinetics on vacuum-evaporated thin platinum films in sulfuric acid solution is thoroughly investigated employing the rotating disc electrode (RDE) method. The nominal thickness of the Pt films is varied from 0.25 to 20 nm and the effect of applied Nafion (R) layer on the ORR activity in 0.5 M H2SO4 solution is evaluated. The electroactive surface area of Pt and the corresponding overall ORR activity decreases with the nominal film thickness. An increase in the hydrogen peroxide yield and a decrease of the ORR specific activity of Pt with decreasing the film thickness is also observed. The Nafion (R) coating slightly increases the hydrogen peroxide production, but does not affect the electrocatalytic activity of Pt. The results obtained with the model system employed herein are important for elucidating the influence of Nafion (R) layer on the ORR kinetics on Pt-based electrocatalysts.