Surface electrochemistry of the anodic Cl2 evolution reaction at Pt. Influence of co-deposition of surface oxide species on adsorption of the Cl? intermediate

By means of analysis of potential relaxation transients, coupled with steady-state kinetic measurements at Pt, the effect of co-deposited OH and O species in the surface oxidation process on the extent of chemisorption of the Cl˙ intermediate in anodic Cl2 evolution has been determined. Experiments have been made on Pt electrodes that had been either freshly ‘reduced’ or ‘pre-oxidized’, in the presence of Cl– ions, for controlled times at various potentials. Coverage by surface oxide film species has a major effect upon the electrode kinetics of Cl2 evolution and this is associated with large changes in the adsorption pseudocapacitance and coverage of the ‘overpotential deposited’ Cl˙ intermediate. The relation of recombination-controlled kinetics to Cl˙ coverage and to the presence of co-deposited OH and/or O species at the Pt surface, is examined.