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 H 2SO 4 or 10 mol dm - 3 NaOH at 20°C. Mo 3d spectra suggested that MoO 2 and Mo(OH) 2 were the main components of the films, with smaller amounts of MoO 3 and possibly Mo 2O 5. 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. © 2012 Elsevier B.V. All rights reserved.