Catalysis of oxygen reduction on electrochemically activated polycrystalline gold by Pd nanoislands in alkaline solution

Catalytic properties of electrochemically activated polycrystalline gold, Au(poly), modified by spontaneously deposited palladium nanoislands with the coverage below a monolayer were examined for the oxygen reduction reaction (ORR) in alkaline solution using the rotating disc electrode (RDE) technique. Atomic force microscopy (AFM) images have shown that the coverage of randomly distributed nanosized Pd islands ranged from 18% to 77%. Cyclic voltammetry characterization involved hydrogen adsorption/desorption on the deposited Pd islands, as well as their oxidation/reduction at more positive potentials. RDE measurements have shown that, although ORR on Au(poly) proceeds partly through 4e-reduction pathway, in the presence of Pd islands it turns completely to 4e-pathway, exceeding the activity of bare Pd(poly). Among different Pd/Au(poly) nanostructures, the ones with Pd coverage of 18% and 30% have shown the highest activity for ORR in alkaline solution