Study of manganese and its oxides by photoelectron spectroscopy

This study enabled the determination of the binding energies of the 2p^1/2, 2p^3/2 and 3p^{1/2 3/2} levels of manganese, in various chemical forms: metal, MnO oxides, Mn₃O₄, Mn₂O₃ and MnO₂ and hydroxide Mn(OH)₂. The oxygen binding energies corresponding to each of these species have been determined. Other forms of oxygen that can also be present on the surface of the samples have been established: oxygen of adsorbed water (OH^- ions) and adsorbed oxygen. The methods of preparation of the various oxides in 'thin layer', based on the thermodynamic stability data of each of the oxide forms, have made it possible to verify discrepancies in these data in the case of the thermal preparation of oxide MnO₂, these deviations being of kinetic origin. Similarly, it has been verified that the oxidation of manganese follows the general laws of metal oxidation. The use of the Pourbaix diagram has been very effective in the formation of oxides. Thus, electrochemical oxidation seems to be a new way for the preparation of these compounds in 'thin layer'. Some properties of prepared substances have been put into evidence. The study of the behaviour of the metal manganese in the presence of water vapour helped to detect the formation of hydroxide.