Mn3O4 and γ-MnOOH powders, preparation, phase composition and XPS characterisation

The paper reports data relative to the preparation of Mn3O4 and gamma-MnOOH powders by following hydrothermal procedures. The mixed valence spinel was prepared starting either from manganous sulphate or chloride and oxidising in suspension (by either air or oxygen) the alkaline precipitate. Manganite was obtained by oxidising manganous sulphate solutions with H2O2, subsequent alkalisation and refluxing. The samples were characterised for phase composition by X-ray diffraction. Pure phase oxides were obtained in the case of both Mn3O4 and gamma-MnOOH when Mn(II) sulphate was used as the precursor. The pure phase samples were submitted to X-ray photoelectron spectroscopy (XPS) investigation, in the case of manganese, for both 2p and 3s spectral regions. The binding energies of the un-fitted experimental Mn peaks compare well with the relative values reported in the literature for the compounds. With the aim of assessing the actual Mn speciation, in the external layers, the fitting procedure of the experimental XPS peaks has been performed by modulating the relative intensities of the spectral components on the grounds of distinct hypotheses consistent with the oxide formulas. The possibility of extending the outcome of this elaboration to the bulk composition of the samples is also discussed. (C) 1998 Elsevier Science B.V.