Electrochemical dissolution of Mn3O4 in acid solutions

The present study deals with the electrochemical reductive dissolution of Mn3O4, which was added to carbon-paste electroactive electrodes (CPEEs) in acid solutions. It was found that in the experimental conditions the thermodynamically stable form of manganese was \( {\text{Mn}}^{{2 + }}_{{{\text{aq}}}} \). Kinetic features of the electrochemical reductive dissolution of Mn3O4, which was realized under potential cycling conditions (+1.0 V→−0.7 V→+1.0 V), were determined by the electrode polarization direction. It was shown that the cathodic reduction of Mn3O4 was accomplished in three stages. Manganese was dissolved in the supporting solution only at the third stage. The first two stages involved solid-phase reactions. The anodic cycling stage included an active dissolution of Mn3O4 and the lower manganese oxide (MnO) accumulated on the electrode surface during the cathodic reduction.