Oxidation states of molybdenum in oxide films formed in sulphuric acid and sodium hydroxide

X-ray photoelectron spectroscopy is used to investigate the oxidation states of molybdenum in thin films formed potentiostatically, over a range of potentials, in either 1 mol dm(-3) H2SO4 or 10 mol dm(-3) NaOH at 20 degrees C. Mo 3d spectra suggested that MoO2 and Mo(OH)(2) were the main components of the films, with smaller amounts of MoO3 and possibly Mo2O5. O 1s spectra indicated the presence of oxygen as oxide and hydroxide species and as bound water. Ion beam analysis revealed the formation of thin films at all potentials, with significant losses of oxidized molybdenum to the electrolyte. (C) 2012 Elsevier B. V. All rights reserved.