Characterization of Thermal Prepared Platinized Tin Dioxide Electrodes: Application to Methanol Electro-Oxidation

Different platinized tin dioxide electrodes were prepared by the thermal decomposition procedure on titanium substrate. They were characterized physically and electrochemically. The platinum modified tin dioxide electrodes developed in this work present rough surface with small cracks. Amorphous SnO₂ and polycrystalline Pt were identified by X-Ray pattern analysis. The platinum particles size vary from 6,6 to 8,9nm indicated their nanostructure. XPS analysis indicates that pure deposits are prepared and their surface is composed of Pt, O, Sn. Deconvolution of the Pt, O and Sn signals revealed that the deposit is composed of SnO₂, zero-valence and oxidised form of Pt. The electrochemical investigation with ferriferrocyanide redox couple showed a quasireversible behaviour on the electrodes. Their electrocatalytic activity increases to reach a maximum for a composition between 40%mol Pt and 70%mol Pt in the deposit. Then after, this activity decreases to reach that of pure platinum. That was related to the distribution of platinum and its size in the deposit. The electrochemical oxidation of methanol on the platinum modified tin dioxide electrodes led to a decrease of its oxidation overpotential in comparison to that of pure platinum. This oxidation begins at potential of about 220mV lower than the pure platinum. The decrease of the overpotential of methanol oxidation is due to the involvement of platinum and tin dioxide in the oxidation process. A mechanism of methanol oxidation has been proposed.