Manganese dioxide electrode—IV. Chemical and electrochemical reduction of an electrolytic γ-MnO2

✍ Scribed by W.C. Maskell; J.E.A. Shaw; F.L. Tye

• Publisher: Elsevier Science
• Year: 1981
• Tongue: English
• Weight: 559 KB
• Volume: 26
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(81)90009-8

✦ Synopsis

The chemical or electrochemical reduction of y_MnO, proceeds via a single phase over the complete range MnO,-MnO,,,. The end member MnO,,, has been named 6-MnOOH to distinguish it clearly from groutite. If the de Wolff model for y-MnO, is accepted then CMnOOH is an intergrowth structure of groutite with miaodomsins of manganite. The oxyhydroxide is metastable in the region MntX7s-MnO,,, slowly precipitating y-MnOOHas a separate phase in aqueous solutions probably by a dissolution-precipitation mechanism.

The filling of the lattice with electrons and protons appears to proceed differently in the ranges Mn02-Mn01,1,andMn01,,,-Mn01,,.

Two ways in which this might come about arc proposed. Evidence from Jahn-Teller distortion favours the explanation that in the first half of reduction an electron entering the structure is delocalised between two adjacent Mn '* ions: in the second half an added electron displaces a shard electron and the two electrons are associated with individual cations forming Mn" + ions.