The influences of temperature and substrate material (platinum, steel 12.18N10T) on the mechanism of the electrochemical oxidation of Mn2+ to MnOx in the acetic acid electrolyte were investigated using hronovoltamperometry method. Analysis of polarization curves at T <= 323 K proved that the hydrolysis reaction like rate-determining step strongly influenced the process of oxide film formation. It was observed the additional oxidation peak currents on i,E - curves at T >= 323 K. It has been interpreted like another manganese oxide film formation mechanism take place. It was experimentally found that the substrate material didn't substantial effect on the MnOx electrodeposition process. The structures of films formed at T >= 333 K was investigated using X-ray diffraction. The polycrystalline coatings consisting of a mixture gamma- MnO2 and Mn3O4 phases with different crystallographic orientation were observed. The analysis of XRD patterns was allowed to estimate the dependence of Mn3+ / Mn4+ ratio in the film from the temperature of coating deposition. It was determined the dependence of the crystalline degree from the temperature of coating deposition. Scanning electron microscopy (SEM) was used to study the morphology of the obtained samples. It was found a significant cracking on the coating obtained at T =323 K. It has been explained changing of hydration degree in the oxide.
THE INFLUENCE OF TEMPERATURE ON MANGANESE OXIDES ELECTRODEPOSITION ON PLATINUM AND STEEL ELECTRODES
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