The Kinetics of Electrode Reactions

In this section, the discussion of the mechanism of hydrogen evolution at metallic surfaces will be used to outline the principles of electrode reaction kinetics. This follows the historic development, since originally hydrogen evolution was considered to be the model example of a simple electrode reaction. The view is not really up-to-date: The theory of electrode kinetics is much more advanced concerning redox reactions such as: Fe2+= Fe3++ e−, involving only a tunneling exchange of electrons with an ion undergoing a change in valence and a rearrangement of the hydration shell only. It is for this type of reactions that an advanced theory is available which, however will be disregarded in the following. Hydrogen evolution certainly is an important half-reaction of corrosion processes, and the principles of kinetics can be demonstrated for this example quite well, if only at the expense of a quantitative quantum-mechanical treatment. For a deeper understanding of electrode kinetics the reader is referred to the literature [1-5].