Electrodeposition of Manganese and Molybdenum Mixed Oxide Thin Films and Their Charge Storage Properties

Manganese and molybdenum mixed oxides in a thin film form were deposited anodically on a platinum substrate by cycling the electrode potential between 0 and +1.0 V vs Ag/AgCl in aqueous manganese(II) solutions containing molybdate anion (MoO4 2-). A possible mechanism for the film formation is as fo...

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Bibliographic Details
Published in:Langmuir 2005-06, Vol.21 (13), p.5907-5913
Main Authors: Nakayama, Masaharu, Tanaka, Akihiro, Sato, Yoshimine, Tonosaki, Tsuyoshi, Ogura, Kotaro
Format: Article
Language:English
Subjects:
Chemistry
Exact sciences and technology
General and physical chemistry
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Summary:Manganese and molybdenum mixed oxides in a thin film form were deposited anodically on a platinum substrate by cycling the electrode potential between 0 and +1.0 V vs Ag/AgCl in aqueous manganese(II) solutions containing molybdate anion (MoO4 2-). A possible mechanism for the film formation is as follows. First, electrooxidation of Mn2+ ions with H2O yields Mn oxide and protons. Then, the protons being accumulated near the electrode surface react with MoO4 2- to form polyoxomolybdate through a dehydrated condensation reaction (by protonation and dehydration). The condensed product coprecipitates with the Mn oxide. Cyclic voltammetry of the Mn/Mo oxide film-coated electrode in aqueous 0.5 M Na2SO4 solution exhibited a pseudocapacitive behavior with higher capacitance and better rate capability than that of the pure Mn oxide prepared similarly, most likely as a result of an increase in electrical conductivity of the film. Electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy clearly demonstrated that the observed pseudocapacitive behavior results from reversible extraction/insertion of hydrated protons to balance the charge upon oxidation/reduction of Mn3+/Mn4+ in the film.
ISSN:0743-7463
1520-5827
DOI:10.1021/la050114u