Thermodynamics of electrodes

The electrodes store chemical energy. The amount depends on the thermodynamic quantity of the Gibbs energy of reaction or differences of 

This Gibbs energy of reaction is converted into the electrical energy zq dSE. Then we have for the cell voltage 

The cell voltage depends on the variation of the Gibbs energy of formation of the electrode compound with the stoichiometry of the electroactive species. Energy is accordingly only stored if chemical work is necessary to add or take away the electroactive component. 

Even more important than the cell voltage is the energy that may be obtained from a galvanic cell as it discharges and the composition of the electrode changes. Integration of Eqn (8.41) provides the following expression 

The difference in the Gibbs energies of formation corresponds to the integral of the cell voltage as a function of the composition between the limits of the starting and the final compositions. The value for ASf° is determined from the variation of the cell voltage as a function of the temperature 

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As we have seen, acidity and basicity are intimately connected with electron transfer. When the electron transfer involves an integral number of electrons it is customary to refer to the process as a redox reaction. This is not the place for a thorough discussion of the thermodynamics of electrochemistry that may be found in any good textbook of physical chemistry. Rather, we shall investigate the applications of electromotive force (emf) of interest to the inorganic chemist. Nevertheless, a very brief review of the conventions and thermodynamics of electrode potentials and half-reactions will be presented. 

It is important to obtain experimental information on the thermodynamics of electrode processes to ascertain the tendency of a particular reaction to occur under a given set of experimental conditions namely temperature, pressure, system com H)sition and electrode potential. Such information is provided by the standard- or formal-electrode potentials for the redox couple under consideration. Appropriate combinations of these potentials enable the thermodynamics of homogeneous redox processes to be determined accurately. However, such quantities often are subject to confusion and misinterpretation. It is, therefore, worthwhile to outline their significance for simple electrochemical reactions. This discussion provides background to the sections on electrochemical kinetics which follow. The evaluation of formal potentials for various types of electrode-reaction mechanisms is dealt with in 12.3.2.2. 

The rate of a corrosion reaction is affected by pH (via H reduction and hydroxide formation), the partial pressnre of O, (the solubility/concentration of oxygen in solution), fluid agitation, and electrolyte condnctivity. Corrosion processes are analyzed using the thermodynamics of electrode reactions, mass transfer of the cathode reactants O2 and/or H, and the kinetics of metal dissolution reactions [157, 158]. 

Y. Wang, E. O. Barnes, E. Laborda, A. Molina, and R. G. Compton. Differential pulse techniques in weakly supported media. Changes in the kinetics and thermodynamics of electrode processes resulting from the supporting electrolyte concentration, J. Electroanal. Chem. 673, 13 23 (2012). 

Effect of Reactant Transport on the Thermodynamics of Electrode Reaction 59... 

Regarding the effect of reactant transport on the thermodynamics of electrode reaction, we have to consider the reversible... 

Ravdel BA, Trebukhova S, Puglia FJ (2009) Thermodynamics of Electrode Materials for Lithium-Ion Batteries. Proceedings of the 216th Meeting of the Electrochem Soc. Vienna, Austria, Oct. 4-9,2009. Abstract 640... 

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