Reference Electrodes
In experimental electrochemistry, it is common to use reference electrodes when controlling current or voltage with a potentiostat. Potential differences in the system are recorded with respect to the equilibrium potential of the redox couple at the reference electrode. A good reference electrode is designed so that no net charge transfer takes place at its electrode-electrolyte interface. Then the overpotential of the reference is zero, so:
(4-19)
where ϕs , ref (SI unit: V) is the electric potential of the reference electrode and Eeq, ref (SI unit: V) is the equilibrium potential of the reference electrode reaction.
The electric potentials of the electrodes in the electrochemical cell can then be defined with respect to the reference electrode according to:
(4-20)
where Evs ref (SI unit: V) is the electrode potential versus the reference potential.
It is important to realize that the presence of an ideal reference electrode in the system has no impact on the physics; the only purpose of the reference electrode is to define a stable reference point for the potential levels.