Metal silicides are promising electrode materials, because they are characterized by a high chemical resistance [1-3] and a low hydrogen overpotential [4,5] in acidic electrolytes. These properties strongly depend both on the nature of the metal component, as well as its amount in the silicide, and on the structural and physical parameters of the silicide itself.Earlier [6-9], we comprehensively studied silicides of iron family metals. It is of great interest to investigate other silicides, which have not yet been studied in electrochemical aspects, in particular, manganese silicides.Here, the corrosion-electrochemical behavior of manganese silicides MnSi and Mn 5 Si 3 in a sulfuric acid electrolyte is extensively studied.The procedures of making the specimens and preparing them prior to investigations, as well as devices, methods of electrochemical measurements, and procedure of electrolyte preparation were similar to those we have already used for iron, cobalt, and nickel silicides [6,7]. Figure 1 gives potentiostatic voltammograms of manganese, silicon, and manganese silicides, which were measured in 0.5 M H 2 SO 4 ; Table 1 lists the data, obtained from the voltammograms. It is seen that, under these conditions, Mn is not passivated in a potential ( E ) range studied. The free-corrosion potential of manganese E cor is approximately -0.7 V (hereafter, the potentials are referred to the standard hydrogen scale). The manganese anodic dissolution rate is high: in a ∆ E range of -0.8 to 1.8 V, the anodic current density rate is 1.3 × 10 3 A/m 2 . The anodic dissolution rate of silicon is by ~ 3 orders of magnitude lower than that of manganese, and E cor of Si is approximately -0.1 V. The manganese silicides show still lower i a . As is seen from Fig. 1, the anodic dissolution rates of Mn 5 Si 3 and MnSi are approximately 5 orders of magnitude lower than that of Mn and by nearly 3 orders lower than that of Si.That is, with an increase in the silicon content in silicide, the silicide's anodic dissolution rate in sulfuric acid solution decreases.It should be noted that the silicon behavior in the above electrolyte is complicated by its inherent semiconductive properties and the presence of SiO 2 film at the electrode surface. It is virtually impossible to determine the mechanism of hydrogen cathodic evolution on silicon based only solely kinetic parameters of voltammograms. Supposedly, the pathway of hydrogen evolution (HE) corresponds to discharge-recombination processes, with the desorption as the limiting stage. On manganese, the limiting stage is the discharge of H 3 O + ions. This is supported by a Tafel slope ( b c ) of 0.146 V and a reaction order of 0.9 determined in this work.Silicon belongs to elements that exceed manganese in the affinity to hydrogen (the breakage energies of Si-H n H + Abstract -The corrosion-electrochemical behavior of Mn 5 Si 3 and MnSi silicides in the sulfuric acid electrolyte is studied by using the steady-state and cyclic voltammetry in combination with atomic absorption analysis. T...
