RODRIGO FERNANDO BRAMBILLA DE SOUZA

RODRIGO FERNANDO BRAMBILLA DE SOUZA

Página do item completo

Resultados de Busca

Agora exibindo 1 - 5 de 5

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.
Amônia: uma nova alternativa para células a combustível alcalinas?
2014 - ASSUMPCAO, MONICA H.M.T.; SILVA, SIRLANE G. da; SOUZA, RODRIGO F.B. de; BUZZO, GUILHERME S.; SPINACE, ESTEVAM V.; NETO, ALMIR O.; SILVA, JULIO C.M. da
PdSn/C electrocatalysts with different atomic rations for ethanol electro-oxidation in alkaline media
2014 - SILVA, SIRLANE G. da; ASSUMPCAO, MONICA H.M.T.; SILVA, JULIO C.M.; SOUZA, RODRIGO F.B. de; SPINACE, ESTEVAM V.; OLIVEIRA NETO, ALMIR; BUZZO, GUILHERME S.
PdSn/C with different Pd:Sn atomic ratios (90:10, 80:20. 70:30, 60:40 and 50:50) were prepared by borohydride reduction and tested for ethanol electro-oxidation in alkaline media. X-ray diffractograms patterns of the obtained materials showed the characteristic peaks of face-centered cubic structure of Pd, however, the PdSn alloy formation was not observed for all electrocatalysts. Also, the peaks of metallic Sn or SnO2 phases were not clearly observed in the diffractograms suggesting the formation of amorphous phases. The electro-oxidation of ethanol was studied by cyclic voltammetry and chronoamperometry at room temperature and PdSn/C (50:50) showed the best performance in these conditions. PdSn/C (50:50) and (90:10) were tested in single fuel cell at 75oC and the highest power density was obtained with PdSn/C (90:10).
Electrochemical and fuel cell evaluation of PtIr/C electrocatalysts for ethanol electrooxidation in alkaline medium
2014 - SILVA, SIRLANE G. da; ASSUMPCAO, MONICA H.M.T.; SOUZA, RODRIGO F.B. de; BUZZO, GUILHERME S.; SPINACE, ESTEVAM V.; OLIVEIRA NETO, ALMIR; SILVA, JULIO C.M.
PtIr/C electrocatalysts prepared by borohydride reduction process were characterized by X-ray diffraction, transmission electron microscopy, and cyclic voltammetry. The X-ray diffraction measurements suggested the PtIr alloy formation; furthermore, peaks of IrO2 were not observed; nevertheless, the presence of Ir oxides in small amounts and amorphous forms cannot be discarded. The transmission electron microscopy showed the average particle diameter between 4.0 and 6.0 nm for all compositions prepared. The catalytic activity for ethanol electrooxidation in alkaline medium at room temperature (cyclic voltammetry and chronoamperometry results) showed that PtIr/C (70:30) and PtIr (90:10) exhibited higher performance toward ethanol oxidation than the other electrocatalysts. Experiments using direct ethanol alkaline fuel cell at 75 °C showed PtIr (90:10) as the best electrocatalyst and Ir/C as virtually inactive for ethanol oxidation in real conditions. The best result obtained using PtIr/C may be associated to the electronic effect between Pt and Ir that could decrease the poisoning on catalyst surface and also by the occurrence of bifunctional mechanism.
Electrochemical and fuel cell evaluation of PtAu/C electrocatalysts for ethanol electro-oxidation in alkaline media
2014 - SILVA, SIRLANE G. da; SILVA, JULIO C.M.; BUZZO, GUILHERME S.; SOUZA, RODRIGO F.B. de; SPINACE, ESTEVAM V.; OLIVEIRA NETO, ALMIR; ASSUMPCAO, MONICA H.M.T.
PtAu/C electrocatalysts in different atomic ratios and supported on Vulcan XC 72 carbon were tested for ethanol electro-oxidation in alkaline media. The electrocatalysts were prepared using borohydride as reducing agent. PtAu/C X-ray diffraction (XRD) patterns showed peaks characteristic of Pt face-centered cubic (fcc) structure and carbon. PtAu/C (70:30) and (50:50) XRD patterns showed a shift to lower values of 2q when compared to Pt/ C, this way suggesting the formation of PtAu alloy. Transmission electron micrographs showed the nanoparticles with particle size between 4 and 6.5 nm for all PtAu/C electrocatalysts. Electrochemical characterization of the PtAu/C materials suggested the PtAu/C (50:50) as the most promising material for ethanol electro-oxidation while experiments in single fuel cell suggested PtAu/C (70:30). The discrepancy in the results obtained can be explained by the electrode construction since PtAu/C (50:50) yields a much thicker electrode than PtAu/C (70:30), due to the Pt load is the same. The best results obtained with PtAu/C electrocatalysts could be explained by the presence of Pt and Au in close contact (alloy) associated to the extend in the platinum lattice parameters since these properties could contribute to the CeC breaking bond.