Electrochemically codeposited platinum molybdenum oxide electrode for catalytic oxidation of methanol in acid solution

An electrochemical codeposition method was used to prepare a Pt/MoOx/C composite electrode which provides a surface modification with catalytic properties for methanol oxidation in acid solution. This method allows the mixing of metal and support on a microscopic level (atomic or molecular scale), i.e., to disperse the Pt microparticles into the molybdenum oxide on a carbon (C) substrate. X-ray photoelectron spectroscopy of the composite electrode presented a broad peak in the Mo (3d) region revealing the existence of Mo6+ species as well as lower valence states such as Mo5+ and Mo4+. Cyclic voltammetry, potentiodynamic voltammetry, and the potentiostatic techniques were also used to characterize the electrode. The composite electrode showed a better performance for methanol oxidation in acidic media than on platinized carbon electrode. A surface redox mechanism which involves (i) the Mo(VI)/Mo(IV) couple in substoichiometric lower valence molybdenum oxides MoOx (2 < x < 3) and (ii) the proton spillover effect from hydrogen molybdenum bronze are two possible explanations for the enhanced catalytic activity of this system. (C) 1999 The Electrochemical Society. S1099-0062(99)04-095-X. All rights reserved.