Reference states for absolute half-cell potentials

Reasons for disagreement regarding reference states for half-cell potentials are discussed. It is suggested that the electron at rest at ∞ is the best choice, and the only one that agrees with common physics practice. This reference state is the same as that just outside the electrolyte for large electrolytes. Choose this case and most disagreement disappears. It is also suggested that an electron at ∞ is a good thermodynamic state, with entropy zero and a Gibbs free energy. For half-cells with different electrolytes it is necessary to refer all Fermi levels to the same reference state.