Interfaces in charge transfer equilibrium

Since the electrochemical potential of electrons in metals is a function of the inner potential of the metal (P ca) = p. a) - e a and PecB) = H (b - te), the inner potential difference, Mmb, across the interface where electron transfer is in equilibrium is represented by the difference in the chemical potential of electrons between the two metal phases A and B is shown in Eqn. 4-8  

Further, since the electrochemical potential of electrons in metals is also a fimction of the outer potential of the metal - e tpx and p, ) = a g) - a f b). fhe 

we consider the interface M/S of a nonpolarizable electrode where electron or ion transfer is in equilibrium between a solid metal M and an aqueous solution S. Here, the interfadal potential is determined by the charge transfer equilibrium. As shown in Fig. 4-9, the electron transfer equilibrium equates the Fermi level, Enn) (= P (M)), of electrons in the metal with the Fermi level, erredox) (= P s)), of redox electrons in hydrated redox particles in the solution this gives rise to the inner and the outer potential differences, and respectively, as shown in Eqn. 4-10  

In the case of ion transfer equilibrium at the electrode interface M/S, the ion level, Pi(M , in the electrode equals the ion level, Pioj, of hydrated ions in the solution as shown in Fig. 4-9. The inner potential difference, is hence 

---