RODRIGO FERNANDO BRAMBILLA DE SOUZA
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Artigo IPEN-doc 27245 Comparison of various atomic compositions of Au@Pd/C, Pd/C, and AuPd/C electrocatalysts for direct ethanol fuel cells2020 - FONTES, ERIC H.; NANDENHA, JULIO; PIASENTIN, RICARDO M.; SOUZA, RODRIGO F.B. de; NETO, ALMIR O.Pd/C, Au@Pd/C (core-shell), and AuPd/C (AR—consisting in Au microparticles) were used as electrocatalysts for ethanol oxidation in alkaline medium. A synergistic effect between Au and Pd atoms in Au@Pd/C makes the binding between ethanol and Au@Pd/C stronger. This leads to product formation in higher potentials and can be useful to select ethanol products. We also showed that the atomic composition of the electrocatalysts to be used in fuel cells and in powder form to be used in electrochemical experiments are very similar, reaching high values of correlation. The depth profiling X-ray photoelectron spectroscopy for the anode catalysts to be used in fuel cells can provide new insights about ethanol oxidation in direct ethanol fuel cells (DEFCs), for instance, metal oxide species can act in fuel cells environment. In terms of electric generation, Au@Pd/C presented a better performance in electrochemical experiments; the current density was about 1.6 times higher than the peak current density obtained for Pd/C. In terms of electrochemical stability, Au@Pd/C presented better final current density when compared to Pd/C and AuPd/C electrocatalysts. However, in DEFC experiments, Pd/C showed better performance.Artigo IPEN-doc 26429 Direct Alkaline Anion Exchange Membrane Fuel Cell to converting methane into methanol2019 - SANTOS, MONIQUE C.L.; NUNES, LIVIA C.; SILVA, LUIS M.G.; RAMOS, ANDREZZA S.; FONSECA, FABIO C.; SOUZA, RODRIGO F.B. de; NETO, ALMIR O.Methane is the main constituent of natural gas and can be converted in higher value-added products for electricity cogeneration. It could be used as a solid membrane reactor (SMR) for application in Alkaline Anion-Exchange Membrane Fuel Cell (AAEMFC). The investigation for the conversion of methane was based on sodium borohydride (NaBH4) method using Pt/C Basf, Pd/C, Ni/C as catalysts. The electrocatalysts were prepared with 20 wt% of metals loading on carbon. The X-ray diffraction (XRD) analysis revealed a face-centered cubic structure (FCC) for Pt/C and Pd/C catalysts, was observed Ni/ NiO phases for Ni/C electrocatalyst. The Transmission Electron Microscopy (TEM) exhibited a good dispersion of nanoparticles and some agglomerations on the support, with a mean size of 6.4 nm for Pd/C, 5.7 nm for Ni/C and near to 2 nm size for Pt/C. The experiments with AAEMFC showed that all materials can carry out the reaction spontaneously. Pt/C catalyst presents energy density higher than the other materials. FTIR data suggest that methane was converted into small products organic molecules such as methanol and formate in different potentials for Pt/C, Pd/C, and Ni/C. The products were quantified by Raman spectroscopy. The high conversion efficiency obtained was about 20% at 0.3 V using Pt/C catalyst, the maximum conversion over Pd/C was 17.5% at 0.15 V, associated with the formation of a thin layer of PdO on the catalytic surface. The highest conversion rate (13%) was observed in closed circuit potentials to the short circuit in the cell with Ni/C catalyst. The results suggest that for the selective conversion of methane to methanol are most promising using materials containing Pt or Pd.Artigo IPEN-doc 19951 Effect of TiOsub(2) content on ethanol electrooxidation in alkaline media using Pt nanoparticles supported on physical mixtures of carbon and TiOsub(2) as electrocatalysts2014 - SOUZA, R.F.B. de; BUZZO, G.S.; SILVA, J.C.M.; SPINACE, E.V.; NETO, A.O.; ASSUMPCAO, M.H.M.T.Pt nanoparticles supported on physical mixtures of carbon and TiO2 (Pt/(C+TiO2) electrocatalyst) were tested for ethanol electrooxidation in alkaline media. The electrocatalysts were prepared with different C/TiO2 mass ratios using borohydride as reducing agent. X-ray diffraction patterns of the obtained materials showed the peak characteristic of Pt facecentered cubic (fcc) structure, carbon, and TiO2 phases. Transmission electron micrographs showed metal nanoparticles distributed preferentially over TiO2 support with average particle size between 5 and 7 nm for all electrocatalysts. The cyclic voltammograms of Pt/(C+TiO2) electrocatalysts in alkaline media showed a decrease of Pt surface area with the increase of TiO2 content. The electrooxidation of ethanol suggests the Pt/(C + TiO2) (40:60) as the most promising electrocatalyst for use in fuel cells since it presents almost the same current density value as that of the others and also slower current density decay in chronoamperometry. Moreover, TiO2 provides oxygen species to promote the CO oxidation, resulting in more activity.Artigo IPEN-doc 19058 Electro-oxidation of ethanol on PtSnRh/C-Sbsub(2)Osub(5)-SnOsub(2) electrocatalysts prepared by borohydride reduction2013 - CASTRO, J.C.; ASSUMPCAO, M.H.M.T.; SOUZA, R.F.B. de; SPINACE, E.V.; OLIVEIRA NETO, A.