Influence of Cation Vacancies on the Electrode Potential of MnO2

The electrode potential of is governed by a solid‐state proton insertion process. The presence of cation vacancies in the lattice is influencing the partition function of the inserted protons. The free enthalpy of the proton insertion process contains a potential energy term. This latter is shown to depend on the cation vacancy fraction and on the degree of reduction. The electrode potential in neutral or alkaline solutions is adequately described by where is the degree of reduction, Avogadro's number, and φ a potential energy term. A quantitative interpretation of φis derived.