Electrochemical Behavior of Mn5Si3 and Mn5Ge3 in Sulfuric Acid Solutions

Electrochemical behavior of Mn5Si3, Mn5Ge3, Mn, Si, and Ge in sulfuric acid solutions is studied by steady-state and cyclic voltammetry. The cathodic process on Mn5Ge3 is defined by the metallic component. During anodic polarization of Mn5Si3, manganese selectively dissolves out of the silicide lattice and silicon that remains on its surface oxidizes to SiO2, with the Si anodic dissolution rate plummeting down (by ∼ 4 orders of magnitude as compared with Mn). The anodic dissolution of Mn5Ge3 leads to ionization of both Mn and Ge. The anodic hardness of Mn5Ge3 is lower than that of Mn5Si3.