Glass substrates were sonicated for 20 min in acetone, then in ethanol, washed with deionized water and dried with Ar stream. The working area of 0.6940 cm 2 of the electrode was defined by a hole laser cut in Kapton tape. The electrochemical formation of the electrodes was carried out by the methods of cyclic voltammetry (CV) and chronoamperometry (CA) with time control. We used electrolytes of composition 0.005 M MnSO4, 0.5 M Na2SO4 with pH 1, pH 2, and pH 3.5, adjusted using H2SO4. All electrochemical experiments were performed using a potentiostat/galvanostat Bio-Logic SAS, model SP-300 in a conventional three-electrode glass cell. An Ag/AgCl/3M KCl was used as reference and a