Kinetics of the bromine/bromide electrode on platinum in aqueous sulphuric acid

The kinetics of the bromine/bromide electrode on platinum in aqueous sulphuric acid have been studied by impedance measurements. The impedance does not obey a Randles circuit but the addition of an adsorption capacity across the diffusion impedance seems to give a satisfactory equivalent circuit. Study of the concentration dependence of the exchange current suggests that the rate-controlling step is Br–⇌ Br+e. The reaction is accelerated by a factor of about 2 by preliminary formation of oxide on the electrode surface.