Electroreduction of oxygen on gold-supported thin Pt films in acid solutions

The electrochemical reduction of oxygen was studied on vacuum evaporated thin Pt films (0.25–20 nm thick) on polycrystalline Au substrate (Pt/Au) in 0.1 M HClO4 and 0.05 M H2SO4 solutions using the rotating disk electrode (RDE) method. The surface morphology of Pt films was examined by scanning tunnelling microscopy (STM). The O2 reduction specific activity of Pt films increased with increasing the film thickness in HClO4, but was lower than that of bulk Pt even for the thickest films. In H2SO4, the specific activity showed no significant dependence on the platinum loading and was lower than in HClO4. The Tafel slope values characteristic to polycrystalline Pt (−120 mV dec−1 and −60 mV dec−1) were found for all electrodes. The RRDE studies of 0.5 nm Pt/Au electrode revealed that O2 reduction predominantly proceeds through 4e− pathway and H2O2 is produced in low quantities.