UNDERPOTENTIAL DEPOSITION OF CADMIUM ON POLYCRYSTALLINE PLATINUM AND ITS INFLUENCE IN THE OXYGEN REDUCTION REACTION

This work describes the study of underpotential deposition (upd) of Cd on polycrystalline platinum in acid and neutral media using cyclic voltammetry and rotating ring-disk electrode techniques. In 0.1 M H2SO4 solutions, the hydrogen desorption peaks overlap those of Cd(ad) turning the charge calculation problematic. To avoid such a situation, Cd upd was deposited in 0.2 M Na2SO4 solution. The results were transposed to acidic medium in order to analyse the effect of Cd upd on the oxygen reduction reaction. It was shown that the presence of Cd upd on the platinum surface inhibits the oxygen reduction reaction. The increase in Cd coverage firstly changes the mechanism of the orr from 4 to 2 electrons and finally inhibits it completely by blocking all the surface active sites.