OXYGEN ELECTROREDUCTION ON TITANIUM-SUPPORTED THIN PT FILMS IN ALKALINE-SOLUTION

The electrochemical reduction of oxygen at thin Pt films prepared on t itanium substrate has been studied in alkaline solution. Tafel plots w ith 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 elec trodes was qualitatively the same in comparison to that of Pt/GC elect rodes. Cyclic-voltammetric experiments revealed that the potential of the hydrogen adsorption-desorption peaks and the platinum oxide reduct ion peak shifted towards positive potentials with the increasing Pt fi lm thickness in 0.1 M KOH and 0.5 M H2SO4. The coverage of platinum su rface with oxygen-containing species (Theta(ox)) was found to be depen dent on Pt film thickness. Theta(ox) plays an important role in determ ining the oxygen reduction kinetics at platinum electrodes. (C) 1997 E lsevier Science Ltd.