PtRu/C electrocatalysts were prepared by hydrothermal carbonization process using starch as carbon sources and reducing agents and platinum and ruthenium salts as catalysts of carbonization process and metals source. pH of the reaction medium was adjusted using KOH or TPAOH (tetrapropylammonium hydroxide). The obtained PtRu/C electrocatalysts were characterized by SEM/EDX, TGA, XRD and cyclic voltammetry. The electro-oxidation of methanol was studied by cyclic voltammetry and chronoamperometry. The PtRu/C electrocatalyst prepared using TPAOH was more active for methanol electro-oxidation than the material prepared with KOH.

The electrocatalytic properties of platinum nanoparticles incorporated into polyaniline films was investigated for oxidation of ethanol in sulfuric acid solutions. The electropolymerization of aniline and the electrochemical depositions of plati-num particles into the polyaniline film were achieved by cyclic voltammetry. The effect of the formation conditions of platinum-modified polyaniline films (as cycle numbers, sweep rates) and alcohol concentra-tion were evaluated. The platinum-modified polyani-line films formed by the optimization conditions can be used as a convenient conducting substrate for the ethanol electrooxidation.

Os eletrocatalisadores PtRh/C, PtSn/C e PtSnRh/C foram preparados pelo método da redução por álcool e caracterizados pelas técnicas de EDX, difração de raios X e voltametria cíclica. A eletro-oxidação direta de etanol foi estudada por voltametria cíclica utilizando a técnica do eletrodo de camada fina porosa. Na região de interesse para aplicações em células a combustível a etanol direto (0,3 a 0,4 V) os eletrocatalisadores PtSn/C e PtSnRh/C se mostraram mais ativos que os eletrocatalisadores PtRh/C.

PtRh/C, PtSn/C and PtSnRh/C electrocatalysts were prepared by the alcohol-reduction process and characterized by EDX, XRD and cyclic voltammetry. The electro-oxidation of ethanol was studied by cyclic voltammetry using the thin porous coating technique. In the region of interest for direct ethanol fuel cell (0.3-0.4V) PtSn/C and PtSnRh/C eletrocatalysts were more active than PtRh/C electrocatalysts.

Pt-Ru/C, Pt-Dy and Pt-Ru-Mo/C electrocatalysts prepared by Bönnemann´s method have been studied as porous thin films on high surface area carbon electrodes, in order to evaluate their electroactivity on CO desorption in PEM fuel cells. For comparison electrode precursor powders with and without thermal treatment were considered. Cyclic voltammetry showed that addition of Mo in the well-established Pt/Ru system is very promising for methanol oxidation. In order to compare the electroactivity of different catalysts a normalization procedure based on the amount of Pt was used.

A reação de eletro-oxidação do metanol foi estudada sobre eletrocatalisadores de Pt/C, PtRu/C e PtMo/C preparados pelo método do ácido fórmico em diferentes composições atômicas. Os produtos da oxidação do metanol foram monitorados pela técnica de DEMS. O desempenho dos catalisadores frente a reação de oxidação do metanol foi estudado através dos perfis voltamétricos e experimentos de cronoamperoometria.

The electro-oxidation of methanol was studied on Pt/C, PtRu/C and PtMo/C. These catalysts were prepared by the formic acid method developed in this laboratory. The products of methanol oxidation were monitored by DEMS experiments. The activity of the catalysts for the oxidation of methanol was studied by cyclic voltametry and cronamperometry.

Novas formulações de eletrocatalisadores ternários do tipo Pt/Ru/Mo foram desenvolvidas pelo método de Bönnemann e caracterizadas pelas técnicas de análise por energia dispersiva de raios X (EDX), difração de raios X (XRD), voltametria cíclica (CV) e curvas de polarização (E vs. i), para a oxidação de H2 , mistura H2/CO e metanol em células a combustível tipo PEMFC. A estrutura dos catalisadores obtida é formada por nanocristais altamente dispersos na matriz de carbono, com 2 nm de tamanho médio da nanopartícula. Os resultados da voltametria cíclica sugerem um aumento considerável da eletroatividade do catalisador com a adição de cocatalisadores. A análise das curvas de polarização sugere que o catalisador ternário Pt/Ru/Mo pode ser interessante do ponto de vista tecnológico.

The synthesis of ternary electrocatalysts Pt/Ru/Mo type were performed according to the Bönnemann method and characterized by the following techniques: energy dispersive analysis (EDX), X-rays diffraction (XRD), cyclic voltammetry (CV) and polarization curves (E vs. i) for the oxidation of H2, H2/CO and methanol in a Proton Exchange Membrane Fuel Cell (PEMFC). Catalysts structure consists of highly dispersed nanocrystals in carbon support, with an average particle size of 2 nm. The results of cyclic voltammetry suggest an enhancement of the catalyst electroactivity with the addition of cocatalysts. Polarization curves indicate that Pt/Ru/Mo systems could be employed as electrode material for PEM fuel cell for technological application.