TOTAL INHIBITION OF THE OXYGEN REDUCTION REACTION AT AU(111) BY COPPER ADLAYERS IN SULFURIC-ACID-SOLUTION

The influence of an underpotentially deposited adlayer of copper on th e oxygen reduction reaction (ORR) at Au(111) has been studied in a 0.0 5 M H2SO4 solution using hanging meniscus rotating disk voltammetry. T he total inhibition of the ORR was found after the formation of the fi rst Cu adlayer. Two possible structures for the Cu adlayer on Au(111) take into account inhibition of the ORR. The total inhibition observed in the present study can be explained by a honeycomb (square-root 3 x square-root 3)R30-degrees structure, rather than a simple (square-roo t 3 x square-root 3)R30-degrees Cu adlayer. A bridging two-site proces s (disproportionation reaction) is not expected to occur on the honeyc omb Cu adlayer.