title: Electrodeposition of manganese and molybdenum mixed oxide thin films and their charge storage properties.
abstract: 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 (MoO(4)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 MoO(4)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.
authors.affiliation: Department of Applied Chemistry, Yamaguchi University, 2-16-1 Tokiwadai, Ube 755-8611, Japan. nkymm@ yamaguchi-u.ac.jp
authors.forename: Masaharu
authors.initials: M
authors.lastname: Nakayama
authors.forename: Akihiro
authors.initials: A
authors.lastname: Tanaka
authors.forename: Yoshimine
authors.initials: Y
authors.lastname: Sato
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Tonosaki
authors.forename: Kotaro
authors.initials: K
authors.lastname: Ogura