Egberto Gomes Franco

Electro-oxidation of methanol and ethanol on Pt-Ru/C and Pt-Ru-Mo/C electrocatalysts prepared by Bonnemann's method

Abstract Pt–Ru/C and Pt–Ru–Mo/C electrocatalysts prepared by Bonnemanns 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. Electrode precursor powders with and without thermal treatment were considered for comparison. The morphology of these precursor powders was characterized in a high-resolution transmission electron microscope equipped with a nano-EDX device and also by XPS measurements. Cyclic voltammetry showed that addition of Mo in the well-established Pt/Ru system is very promising for methanol and ethanol oxidation. Infrared spectroscopic measurements revealed that a thermal treatment in a hydrogen atmosphere of the electrode precursor material was necessary to enhance the efficiency. In order to compare the electroactivity of different catalysts a normalization procedure based on the amount of Pt was used.

Métodos de preparação de nanopartículas metálicas suportadas em carbono de alta área superficial, como eletrocatalisadores em células a combustível com membrana trocadora de prótons

Fuel cells are attracting much interest as efficient and clean energy conversion devices. The main components of low temperature fuel cells are the electrocatalysts used to promote the anodic and cathodic reactions, which are based on platinum and platinum alloys. These electrocatalysts are normally prepared in the form of metal nanoparticles supported on a conductive material, usually high surface area carbon, to improve catalyst utilization and reduce cost. This work presents and comments some methods used presently to produce these electrocatalysts. The performances of the produced electrocatalysts are compared to that of state-of-the-art commercial E-TEK electrocatalysts.

Synthesis and Characterization of PtRu/C Catalysts Obtained by Colloidal and Deposition Methods for Fuel Cell Applications

The purpose of this investigation was to compare catalysts produced by the Bonnemann - colloidal method (PtRu (B1) and PtRu (B2)), and those produced by the spontaneous deposition method (PtRu (SD)). The catalysts produced by both methods had good electrochemical behavior for methanol oxidation for proton exchange membrane fuel cell applications. The structure of the catalyst was examined by transmission electron microscopy (TEM). Energy dispersive spectroscopic analysis (EDS) was used to determine the semi-quantitative composition of the catalysts, and the electrochemical behavior was determined by cyclic voltammetry (CV). The diffractograms of the binary catalysts revealed platinum and ruthenium as the only crystalline phases, as per ICDD data base. The PtRu (B1) catalyst, treated in a reducing atmosphere, has the same structure as PtRu (B2), treated in an oxidising/reducing atmosphere, except that the crystallite size was around 1.7 nm for PtRu (B1) instead of 9.9 nm for PtRu (B2). The catalysts PtRu (B2) and PtRu (SD) showed similar cyclic voltammetric behavior, which was better than that of PtRu (B1). Both methods are suitable for the production of electrocatalysts for fuel cell applications. The colloidal method is more expensive than the deposition method, but the former permits the production of ternary and quaternary catalyst systems with enhanced CO tolerance.

Synthesis and Characterization of Eletrocatalyst Powders for Application in PEM Fuel Cells

The Bonnemann method was chosen to synthesize carbon-supported Pt-Ru-Mo electrocatalyst powders, as this method leads to highly-dispersed nanoparticles with an average particle size of approximately 2 nm. Structural characterization of the resulting catalysts was done by the following techniques: X-rays fluorescence analysis (XFA) and nanosize-energy dispersive X-rays analysis (nano-EDX) to obtain information about noble metal loading and composition as well as X-rays diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) to determine structure, dispersion and crystallite size of the nanoparticles. X-rays photoelectron spectroscopy (XPS) was applied to detect amorphous phases and to determine the oxidation states of Pt, Ru and Mo. The morphology of membrane electrode assemblies, prepared by a spraying technique, was checked by scanning electron microscopy (SEM). For the determination of the electrocatalytic activity E/i curves in single cell arrangements were recorded using both H 2 /CO mixtures and methanol as feed gases.

Characterization of Proton Exchange Membrane Fuel Cell Cathode Catalysts Prepared by Alcohol-Reduction Process

Pt/rare-earth cathode catalysts were synthesized by the alcohol-reduction process and its structure was investigated by transmission electron microscopy (TEM), energy dispersive analyses (EDS), X-ray Diffraction (XRD). The electrochemical behavior of the cathode catalyst was analyzed by cyclic voltammetry (CV) chronoamperommetry (CA).