Unfolding the Hidden Reactions in Galvanic Cells
The relationship between the potential of the cell reaction (Ecell), the entropy change (ΔS), and the enthalpy change (ΔH) 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.
KeywordsPourbaix diagrams Galvanic cells Corrosion Open circuit potential Thermodynamic measurements
We also acknowledge Dr. Samuel Perry for manuscript editing.
All authors have given approval to the final version of the manuscript.
We thank the NSERC, CFI, CSACS, and CQMF for financial support.
- 3.SongC, ZhangJ, InPEM Fuel Cell Electrocatalysts and Catalyst Layers: Fundamentals and Applications ed. By ZhangJ. (Springer, London, 2008) pp 89–134Google Scholar
- 4.A.J. Bard, L.R. Faulkner, in Electrochemical Methods: Fundamentals and Applications, 2nd edn.. Potentials and thermodynamics of cells (Wiley, New-York, 2001), pp. 44–82Google Scholar
- 10.A.J. Bard, R. Parsons, J. Jordan, Standard Potentials in Aqueous Solution (Marcel Dekker, New-York, 1985) 1988Google Scholar
- 13.T. Grundl, Chemosphere (3), 613–626 (28, 1994)Google Scholar
- 14.PourbaixM, Atlas of Electrochemical Equilibria in Aqueous Solutions (trans: Franklin JA). 2nd edn.National Association of Corrosion Engineers, Houston, Texas, 1974)Google Scholar
- 16.KeilP, Lutzenkirchen-HechtD, FrahmR In X-Ray Absorption Fine Structure-XAFS13 vol 882, ed. By HedmanB, PainettaP (Aip Conference Proceedings ,2007) pp 490–492Google Scholar
- 20.C.F. Baes, R.E. Mesmer, The Hydrolysis of Cations (Wiley, New York, 1976), pp. 359–362Google Scholar
- 24.W.M.L.D.R. Haynes, CRC Handbook of Chemistry and Physics: a Ready-Reference Book of Chemical and Physical Data (CRC Press, Boca Raton, Florida, 2011)Google Scholar
- 26.MoulderJF, ChastainJ. Handbook of X-ray Photoelectron Spectroscopy: a Reference Book of Standard Spectra for Identification and Interpretation of XPS Data. (Physical Electronics Division, Perkin-Elmer Corporation, 1992)Google Scholar