Electrocatalysis and the chlorine evolution reaction

The chlorine evolution reaction has been investigated on D.S.A. type electrodes in 5.13 M NaCl solution. A large amount of potentiostatic current—potential and impedance—potential data has been collected over a wide potential and frequency range. The current—potential and impedance—potential data has been reduced by curve fitting to a series of a parameter curves. The impedance—potential data were analysed by two methods: an equivalent circuit and the parameter curves CdlE, RctE, RωE reported, and a reaction mechanism and the parameter curves CdlE, kSHE, RωE reported. The two ways of analysing the impedance data are equivalent. However the analysis into a reaction parameter has the advantage that all the data, current—potential and impedance—potential, can be tested using a single set of parameters (kSH, Rω, a, b, DA, DB, δ).In this work the data is compared to that expected for a redox reaction. Any deviation from the expected behaviour of a perfect redox reaction is ascribed to Cl2 bubble formation and to electrode structure effects. It is suggested that the parameter curves are related also to bubble formation characteristics and the ‘real’ area of the electrode.