Unfolding the Hidden Reactions in Galvanic Cells

The relationship between the potential of the cell reaction ( E cell ), the entropy change (Δ S ), and the enthalpy change (Δ H ) is well established. Yet, there is surprisingly a very narrow range of experimental aqueous galvanic cells that follow thermodynamic predictions. The redox and equilibrium reactions used within Pourbaix diagrams are presented a priori to establish the limitations and application range of thermodynamic relationships within complex electrochemical systems, the Zn-Cu (Daniell cell) and Pb-Cu cells. These are then tested to validate the theoretical discussion. Specifically, the electromotive force of both cells is measured as a function of the temperature in order to calculate the thermodynamic properties of the reaction: concomitantly to the voltage measurements, the temperature, the pH, and the surface state of the electrodes. Graphical Abstract