Journal of the Electrochemical Society, Vol.141, No.9, 2422-2429, 1994
Electrochemical Oxidation of Manganese(II) in HClO4 Solutions
The electrochemical oxidation of M(II) has been investigated using voltammetric and in situ spectroelectrochemical techniques at platinum, gold, lead dioxide, and bismuth-doped lead dioxide electrodes. Various experimental parameters exerted significant effects on the oxidation process and its products. The Mn(III) or MnO4- species is produced depending on the electrode potentials, concentrations of Mn(II), voltage scan rates, and initial potentials during potential scans. These effects are discussed in terms of the equilibrium reactions between Mn(III) and MnO2 films at the electrode surface and relative stabilities of the products. While a catalytic mechanism is shown to be operative in the case of the oxidation of Mn(II) into MnO4- at PbO2 and Bi-doped PbO2 electrodes, it does not appear to play an important role during the oxidation to Mn(III). The Mn(III) is shown to be produced from a very early stage of the anodic potential scan and to undergo disproportionation-conproportionation reactions depending on the relative concentration of each species near the electrode surface.