UNDERPOTENTIAL DEPOSITION OF LEAD ON POLYCRYSTALLINE PLATINUM AND ITSINFLUENCE ON THE OXYGEN REDUCTION REACTION

This work describes the study of underpotential deposition (upd) of Pb on polycrystalline platinum in 0.2 M HClO4 solutions using cyclic vol tammetry and rotating ring-disk electrode techniques. In such conditio ns, a full monolayer of upd Pb corresponds to a coverage of 0.41. The adsorption of lead inhibits the adsorption of hydrogen in a non-select ive way. This behavior was explained through the comparison between th e radius of the ad-atom and the substrate. It was calculated that each Pb ad-atom occupies two sites in the surface. Additionally it is show n that the presence of upd Pb significantly inhibits the oxygen reduct ion reaction. This effect was associated to the formation of H2O2 as t he final product, instead of H2O.