ABSTRACT
Electrode kinetics tells us that copper metal is indeed dissolving anodically to form cupric ions. However, it is doing so at a rate that is exactly matched by the rate at which cupric ions are plating back cathodically onto the metal surface. The word “polarisation” is also sometimes linked with words indicating the cause of the change in potential, such as “activation polarisation”, “resistance polarisation” and “concentration polarisation”. In the case of the oxygen electrode, shifting the potential in a negative (cathodic) direction initially gives rise to Tafel-type behaviour. The rate of the reaction is controlled by the activation energy, so the Butler-Volmer equation is obeyed. However, the rate of reduction of oxygen on the surface soon reaches a point at which the molecules are reduced as fast as they can diffuse to the metal surface from the bulk solution.
