RODRIGO FERNANDO BRAMBILLA DE SOUZA

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Autor: ESTEVAM VITORIO SPINACE × Percentil: 75.00 - 100.00 ×

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    Artigo IPEN-doc 20890
    PtAu/C electrocatalysts as anodes for direct ammonia fuel cell
    2015 - SILVA, JULIO C.M.; SILVA, SIRLANE G. da; SOUZA, RODRIGO F.B. de; BUZZO, GUILHERME S.; SPINACE, ESTEVAM V.; OLIVEIRA NETO, ALMIR; ASSUMPCAO, MONICA H.M.T.
    PtAu/C electrocatalysts prepared by borohydride reduction method with different Pt:Au atomic ratios (50:50 and 70:30) were tested as work electrodes/anodes in electrochemical experiments and also using a direct ammonia fuel cell (DAFC). X-ray diffraction patterns showed the formation of PtAu alloy while transmission electron micrographs showed the particles sizes between 5.8 and 6.4 nm. PtAu/C 70:30 presented the best results showing a current density about 20% higher when compared to Pt/C in voltammetry experiments and a power density about 60% higher than Pt/C using DAFC, while Au/C showed practically no activity in both experiments. The best results obtained with PtAu/C (70:30) could be explained by the electronic effect (PtAu alloy) associated with adsorbed hydroxyl species (AuOHads) and also the lower Au-N energy adsorption.
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    Artigo IPEN-doc 20873
    Oxidation of ammonia using PtRh/C electrocatalysts: fuel cell and electrochemical evaluation
    2015 - ASSUMPCAO, MONICA H.M.T.; PIASENTIN, RICARDO M.; HAMMER, PETER; SOUZA, RODRIGO F.B. de; BUZZO, GUILHERME S.; SANTOS, MAURO C.; SPINACE, ESTEVAM V.; OLIVEIRA NETO, ALMIR; SILVA, JULIO C.M. da
    This study reports on the use of PtRh/C electrocatalysts prepared by the borohydride reduction method with different Pt:Rh atomic ratios: (90:10, 70:30 and 50:50) which was investigated toward the ammonia electro-oxidation considering electrochemical and also direct ammonia fuel cell (DAFC) experiments. The DAFC experiments were conducted using different proportions of NH4OH and KOH as fuels. X-ray diffraction showed the formation of PtRh alloy while transmission electron micrographs showed the particles sizes between 4.1 and 4.5 nm. Among the different NH4OH and KOH concentrations the combination of 3 mol L−1 NH4OH and 3 mol L−1 KOH was the most favorable due to the higher KOH concentration, which increased the electrolyte conductivity, thus, improving the ammonia oxidation. Moreover, among the PtRh/C electrocatalysts the Pt:Rh ratio of 90:10 showed to be the best suited one since it showed a power density almost 60% higher than Pt. X-ray photoelectron spectroscopy results revealed for this catalyst that the nanoparticles contain a high proportion of metallic Pt and Rh phases, supporting the alloy formation between Pt and Rh. The improved fuel cell efficiency can be related to the combination of different effects: the alloy formation between Pt and Rh (electronic effect), suppressing the adsorption strength of poisonous intermediates, and a synergic effect between Pt and Rh at this composition.