Molybdenum-modified platinum electrodes

Khanfar, Mohammad F. (2003) Molybdenum-modified platinum electrodes. Masters thesis, Memorial University of Newfoundland.

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Abstract

The modification of Pt electrodes with Mo compounds improves their catalytic activity toward the oxidation of methanol and formaldehyde in acidic solutions. The two sets of Mo oxides that have been studied in this work are the Hydrogen Molybdenum Bronze, HₓMoO₃, 0<x<2, and the Molybdenum Oxides, MoOₓ, 2<x<3. -- It has been found that the bronze (H₂MoO₃)ads is generated at the Pt surface in an in situ fashion upon the application of potentials more negative than 0 vs. Ag/AgCl. At higher positive potentials, the adsorbed bronze is oxidized to several intermediates that interact with methanol and facilitate its oxidation on the Pt surface. The nature of the interaction between the adsorbed intermediates and methanol needs further experimental investigation. -- The deposition of MoO₃ on the surface of a commercial carbon supported Pt catalyst, has been achieved. The catalytic promotion observed with the modified catalyst over its unmodified counterpart has been explained in terms of the bi-functional mechanism introduced by Watanabe and Motoo. The activity of the Mo modified catalyst increases with the elevation of the MoO₃ surface concentration to a certain limit, then it decreases with further Mo addition. The extra MoO₃ content shields the Pt sites from the methanol or the formaldehyde molecules. In addition, it is added at the expense of the carbon content of the catalyst that is required for the electronic conductivity through the modified electrode.

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