Cyclic Voltammetry Study of the Mn-Substituted Polyoxoanions [MnII4(H2O)2(H4AsW15O56)2]18- and [((MnIIOH2)MnII2PW9O34)2(PW6O26)]17-: Electrodeposition of Manganese Oxides Electrocatalysts for Dioxygen Reduction

The electrochemical behavior of two manganese (Mn)-substituted polyoxoanions, the dissymmetrical Dawson sandwich-type [Mn-4(II)(H2O)(2)(H4AsW15O56)(2)](18-) and the Keggin sandwich banana-shaped [(((MnOH2)-O-II)(Mn2PW9O34)-P-II)(2)(PW6O26)](17-) is investigated. At pH 5, the oxidation of the Mn-II-centers results in one oxidation wave for [Mn-4(II)(H2O)(2)(H4AsW15O56)(2)](18-) and two oxidation waves for [(((MnOH2)-O-II)(Mn2PW9O34)-P-II)(2)(PW6O26)](17-). To the best of our knowledge, presence of the second Mn-based wave is rarely observed in the electrochemistry of Mn-containing polyoxometalates. Deposition of Mn-oxides electrocatalysts for dioxygen reduction is noticed by cyclic voltammetry, which can be distinguished by the significant positive shift in potentials of the dioxygen reduction reaction.