Spectroelectrochemical investigation of MnO2 electro-generation and electro-reduction in acidic media

Spectroscopic investigations of Mn²⁺ electro-oxidation and MnO₂ electro-reduction in acidic media (0.5–2 M H₂SO₄) have been performed using optically transparent electrodes (OTE). Reticulated vitreous carbon (RVC) has been used as the electrode material. Our results show that in the first step of Mn²⁺ ions electro-oxidation the unstable in aqueous media Mn³⁺ ions are formed. In the next step Mn³⁺ ions can hydrolyse to MnOOH and/or disproportionate to Mn²⁺ and Mn⁴⁺ ions. Contrary to the electro-oxidation of Mn²⁺ to MnO₂, the electro-reduction of MnO₂ proceeds in two steps. The first step is strictly connected with electro-generation of MnOOH and the next with regeneration of Mn²⁺ ions.