Manganese dioxide electrode—X. A theoretical treatment based on the concept of two solid solutions in the range γ-MnO2 to δ-MnOOH

✍ Scribed by F.L. Tye

• Publisher: Elsevier Science
• Year: 1985
• Tongue: English
• Weight: 684 KB
• Volume: 30
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(85)80053-0

✦ Synopsis

Models are presented which account for the electrode potential of electrodeposited gamma manganese dioxide and its reduction products, MnOOH, in the range 0 < r < 1 and which in particular explain the distinct change in potential us r slope at the mid-reduction point. Two solid solutions are proposed, one with end-members MnO, and MnOOH,., operating in the range r < 0.5 and theother with end-members MnO, and MnOOH operating in the range r z 0.5. TheGibbs Free Energy of the solid solutions and thence electrode potential is derived on the basis of the sites available for placement of inserted protons and electrons, the number of possible arrangements of protons and electrons on the sites and the independence of proton and electron arrangements. Standard Free Energies are derived for y-MnO Ir MnOOHO.s and &MnOOH at 25°C. B. This applicable range of a model is shown by a full line. The models, which lead to relatively simple expressions for potential, match the experimental data closely and the transition from model B to model A provides a basis for the change of slope at the midreduction point. Acknowledgements-The author is pleased to record that this paper has benefited from discussions with his former colleagues Dr W. C. Maskelllll and Dr J. E. A. Shaw. They however prefer the approach presented in parts VIII and XX[9, IS].