The role of anions in the electrochemical behaviour of thick palladium oxide layers

Abstract

The Influence of chloride ions on the elec trochemical hehaviour of palladium oxide films grown at 2.00 V in 1 M H2SO4 + x M HCl (0 < x < 10-5) is investigated by means of voitamilletry. rotating ring-disk and potential step techniques. Both volltammetric and current transients electro reduction data show that the presence of Cl- ions accelerate the electroreduction of palladium oxide films. The potential of the (Electroreduction voltammetric peak increases with the chloride concentration. Cathodic current transients show current maxima related to the presence of a nucleation and growth process. The mechanism of palladium oxide layer electroreduction can be interpreted through the formation of chloride containing complex species which favours the electroreduction by decreasing the time needed to start the nucleation and growth of the new electroreduced phase. This effect is achieved by the breakdown of the anodic layer. The results are discussed within the frame of da ta previously obtained for perchlorale, phosphate and sulphate ion-containing solution.