The bromine electrode Part II: reaction kinetics at polycrystalline Pt

The kinetics of bromide oxidation and Br3− reduction were studied at polycrystalline Pt electrodes in acidic media. The electrochemical behavior of equimolar Br3− and Br− solutions was investigated, in a concentration range of the electroactive species between 0.1 and 1.0 M. E–log j plots did not exhibit linear segments, most probably because of extensive adsorption of bromine radicals. Further analysis supported the hypothesis of a Volmer–Tafel mechanism, with the chemical recombination step as rate determining. Electrosorption isotherms for Br radicals were found to be of the Frumkin type. The kinetics of Br3− reduction was controlled by the surface dissociation of the Br2 molecules.