The Bromine Electrode. Part I: Adsorption Phenomena at Polycrystalline Platinum Electrodes

A cyclic voltammetric study of the behaviour of Br− and Br−3 at Pt electrodes, in the potential range between hydrogen and oxygen evolution, is described. Different experiments were carried out, in the presence of Br− and Br−3, in which the ratio between the species has been kept constant and equal to 1. The halide concentration was varied between 4 × 10−6 and 1 × 10−3 and mol dm−3, at constant ionic strength, in 1 M HclO4 as well as in 1 M NaClO4 adjusted to a pH of 2. Underpotential deposition of Br is observed at potentials as low as −0.125 V vs SCE. The adsorption parameters of Br species were determined from the adsorption/desorption peak pair in the hydrogen adsorption/desorption region, and from the oxide reduction peak data. In the absence of oxygen adsorption, a relatively high coverage of the electrode surface is attained. A Langmuir-type adsorption is observed under the different experimental conditions.