Next, I am interested in the state where no current is transferred calling it the formal state, superscript ∘≀ (for standard activities, Eq. 8c) and the equilibrium state, superscript 𝑒𝑞 (for equilibrium/bulk activities, Eq. 8d), analogous to the B-V model. In the derivation it becomes useful to acknowledge that the difference in effective charges of the bulk states must be equal to the number of transferred electrons (Eq. 8b). This yields the formal potential as depicted Eq. 8c, identical to the Nernst equation.