Oxygen electroreduction on titanium-supported thin Pt films in alkaline solution

The electrochemical reduction of oxygen at thin Pt films prepared on titanium substrate has been studied in alkaline solution. Tafel plots with two different slope regions were observed for oxygen reduction in 0.1 M KOH. At low current densities the slope was around - 60 mV dec(-1), whereas at high current densities the slope was varying between - 260 and - 490 mV dec(-1). The oxygen reduction behaviour at Pt/Ti electrodes was qualitatively the same in comparison to that of Pt/GC electrodes. Cyclic-voltammetric experiments revealed that the potential of the hydrogen adsorption-desorption peaks and the platinum oxide reduction peak shifted towards positive potentials with the increasing Pt film thickness in 0.1 M KOH and 0.5 M H2SO4. The coverage of platinum surface with oxygen-containing species (Theta(ox)) was found to be dependent on Pt film thickness. Theta(ox) plays an important role in determining the oxygen reduction kinetics at platinum electrodes. (C) 1997 Elsevier Science Ltd.