The concept and physical meaning of absolute electrode potential

The concept and the physical meaning of “absolute” electrode potential have been revisited in the light of recent discussion with the purpose of providing a unifying approach to this long-standing problem. It is shown that three single-electrode potentials can be identified by using electrons as test charges and following the only three possible routes to go from one terminal of the cell to the other. Each potential entails referring the electronic energy to a different energy state and writing the electrode reaction, in a different fashion. The relationships between pairs of electrode potentials are shown and their physical meaning is illustrated by means of sketches and equations. It is proved that the Galvani potential difference (Δφ) cannot be regarded as an “absolute” electrode potential. Some previous inadequate views are reassessed.