SERS study of hydrogen peroxide electroreduction on a Pb-modified Au electrode

The mechanism of the electroreduction of H₂O₂ on a Pb-modified Au surface was examined by surface-enhanced Raman spectroscopy. The measurements show the presence of lead peroxide, PbOOH⁺, with the maximum intensity at potential just positive of underpotentially deposited Pb, and bimetallic dihydroxide, AuPb(OH)₂, at potential just positive of that where peroxide is reduced and Pb islands maximally formed on the surface. All the modes for these two species decay rapidly and even disappear as the reduction current flows. Both species are absent in solutions not containing either Pb²⁺ or H₂O₂. The edge of Pb islands on the Au surface is thus shown to be the active site for this catalysis process. These results further underscore the important role of M-OH species in the peroxide electroreduction reaction.