Sol–gel method to prepare active Pt–RuO2 coatings on carbon powder for methanol oxidation

Platinum/ruthenium coatings show promising electrocatalytic properties as anode materials for the direct methanol fuel cell. Various studies in this field indicate that the electrocatalytic properties are highly sensitive to the utilized coating method. Aiming to make anodes with high surface area and activity, the sol–gel method is utilized in this work for the first time to form Pt–RuO2 deposits on a carbon black substrate. Pt–RuO2/C materials with various loadings of the active phase were obtained and their activity toward methanol electrooxidation was investigated by cyclic voltammetry. The results of this investigation show higher activity of the Pt–RuO2/C anodes prepared by the sol–gel method as compared to commercial state-of-art catalysts with similar Pt–Ru loading. The simplicity of the sol–gel deposition method with respect to other preparation procedures and the good electrocatalytic properties of the obtained Pt–RuO2/C anodes encourage further research in this field. Keywords: Carbon powder electrodes, Fuel cells, Catalyst, Methanol, Sol–gel, Platinum, Rutheniu

Electro-oxidation of methanol and ethanol using a Pt-RuO2/C composite prepared by the sol-gel technique and supported on boron-doped diamond

A detailed description of the preparation, characterization and electrochemical performance towards methanol and ethanol oxidation in acid medium of a platinum–ruthenium oxide carbon powder composite is presented here. The composite was prepared by the sol–gel technique and fixed on the surface of a boron-doped diamond (BDD) electrode. The physical characterization by XRD and EDX revealed the crystalline nature of the catalysts particles having an average size of 7.2 nm and a mass ratio of practically 1:1 for Pt and Ru, in accordance with the preparation conditions. Initial electrochemical experiments using also glassy carbon as the substrate for the composite showed that BDD has a superior performance, probably related to the very low capacitive currents of that material. The oxidation of methanol and ethanol in H2SO4 solutions was studied by cyclic voltammetry, Tafel plots and chronoamperometry and the results were compared to those obtained using a commercial Pt/C powder composite under the same conditions. In all cases, the Pt–RuO2/C composite showed larger anodic current densities and increased stability than the other material thus confirming the suitability of the simple and straightforward preparation technique for the catalysts

Amorphous palladium-silicon alloys for the oxidation of formic acid and formaldehyde. A voltammetric investigation

The electrocatalytic oxidation of formic acid and formaldehyde on Pd and on amorphous Pd(Si) was studied by cyclic voltammetry and the results compared with the literature for similar systems. The oxidation of HCOOH on Pd occurs through direct catalytic dehydrogenation via (:C(OH)2)ads while on Pd(Si) this intermediate does not appear to be formed. This is a consequence of the presence of inert Si on the surface that diminishes the probability of adjacent free sites. At high HCOOH concentrations, that intermediate undergoes dehydration on the Pd surface and COads oxidation peak is observed. For HCHO, the oxidation mechanism on both electrode materials appears similar to that previously proposed for Pt. However, the oxides formed on the amorphous Pd(Si) alloy are more reactive than those on Pd thus affecting the overall kinetics of the process for both organic molecules, a fact revealed by the increase in anodic currents observed in the voltammograms