The pre‐exponential factor and its importance in determining mechanism: the bromine electrode

The rate of the reaction 2Br− = Br2 + 2 e at Pt electrodes has been studied in the temperature range 0 – 50 °C. Hence the enthalpy of activation was found to be 15 kJ mol−1. The preexponential factor was calculated using various assumptions and it is shown that the most probable rate‐determining step in this reaction is Br− → Br (ads) + e, the adsorbed bromine atom being in a sparsely filled second layer with the electrode covered completely with a first layer of unreactive bromine atoms.