Ethanol electro-oxidation in an alkaline medium using Pd/C, Au/C and PdAu/C electrocatalysts prepared by electron beam irradiation

Carbon-supported Pd, Au and bimetallic PdAu (Pd:Au 90:10, 50:50 and 30:70 atomic ratios) electrocatalysts were prepared using electron beam irradiation. The obtained materials were characterized by energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and transmission electron microscopy (TEM), and their catalytic activities toward ethanol electro-oxidation were evaluated in an alkaline medium using electrochemical techniques, in situ attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR) analysis and a single alkaline direct ethanol fuel cell (ADEFC). EDX analyses showed that the actual Pd: Au atomic ratios were very similar to the nominal ones. X-ray diffractograms of PdAu/C electrocatalysts evidenced the presence of Pd-rich (fcc) and Au-rich (fcc) phases. TEM analysis showed a homogeneous dispersion of nanoparticles on the carbon support, with an average size in the range of 3-5 nm and broad size distributions. Cyclic voltammetry (CV) and chronoamperometry (CA) experiments revealed the superior ambient activity toward ethanol electro-oxidation of PdAu/C electrocatalysts with Pd: Au ratios of 90:10 and 50:50. In situ ATR-FTIR spectroscopy measurements have shown that the mechanism for ethanol electro-oxidation is dependent on catalyst composition, leading to different reaction products, such as acetaldehyde and acetate, depending on the number of electrons transferred. Experiments on a single ADEFC were conducted between 50 and 900 C, and the best performance of 44 mW cm-2 in 2.0molL-1 ethanol was obtained at 850C for the Pd:Au 90:10 catalysts. This superior performance is most likely associated with enhancement of ethanol adsorption on Pd, oxidation of the intermediates, the presence of gold oxide-hydroxyl species, low mean particle diameters and better distribution of particles on the support. © 2013 Elsevier Ltd. All rights reserved.

The oxidation of hydroxylamine on Pt-, and Pd-modified Au electrodes in aqueous electrolytes: Electrochemical and in situ spectroscopic studies

The electrooxidation of hydroxylamine, NH2OH, in 0.1 M phosphate buffer (PB, pH = 7) on Pt-, and Pd-modified Au electrodes prepared by galvanic displacement of underpotential deposited Cu, was investigated by electrochemical techniques and three and in situ vibrational probes, substrate-induced surface enhanced Raman scattering, SI-SERS, surface enhanced infrared absorption, SEIRAS, and Fourier transform infrared reflection-absorption, IRAS, spectroscopies. Analyses of the results obtained made it possible to identify at low overpotentials, solution phase (sol) and adsorbed (ads) nitric oxide, NO, as well as solution phase nitrous oxide, N2O. As the potential was increased, the peak(s) ascribed to NO(ads) gained in intensity and new features associated with NO2−(ads) and NO2−(sol) were clearly discerned. Further excursion toward higher potentials yielded an additional peak assigned to NO2(ads). This behavior is analogous to that found for bare Au electrodes in a potential region in which the metal is at least partially oxidized under otherwise the same experimental conditions.

Quantificação eletroquímica de analitos de interesse ambiental e biológico, empregando novos materiais preparados a partir de silsesquioxanos funcionalizados

Pós-graduação em Ciência dos Materiais - FEIS

Electrochemical oxidation of landfill leachate in a flow reactor: optimization using response surface methodology

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Determination of salicylate in blood serum using an amperometric biosensor based on salicylate hydroxylase immobilized in a polypyrrole-glutaraldehyde matrix

The use of an amperometric biosensor for the salicylate determination in blood serum is described. The biosensor is based on salicylate hydroxylase (EC 1.14.13.1) electropolymerized onto a glassy carbon-working electrode with polypyrrole and glutaraldehyde, to improve the biosensor lifetime. The hexacyanoferrate (II) was also incorporated to work as a redox mediator to minimize possible interferences. The salicylate is enzymatically converted to catechol, which is monitored amperometrically by its electrooxidation at +0.170 V versus SCE (saturated calomel electrode). Salicylate determination was carried out maintaining the ratio between β-NADH and salicylate at 4:1 (30°C). The amperometric response of the biosensor was linearly proportional to the salicylate concentration between 2.3 x 10-6 and 1.4 x 10-5 mol l- 1, in 0.1 mol l-1 phosphate buffer (pH 7.8), containing 0.1 mol l-1 KCl and 5.0 x 10-4 mol l-1 Na2H2EDTA, as supporting electrolyte. The recovery studies, in the presence of several interfering compounds, showed recoveries between 96.4 and 104.8%. The useful lifetime of the biosensor in the concentration range evaluated was at least 40 days, in continuous use. Blood serum samples analyzed by this biosensor showed a good correlation compared to the spectrophotometric method (Trinder) used as reference, presenting relative deviations lower than 7.0%. (C) 2000 Elsevier Science B.V.

Electrochemical investigation of the voltammetric determination of hydrochlorothiazide using a nickel hydroxide modified nickel electrode

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

O desenvolvimento de nanopartículas de intermetálicos ordenados de ouro e estudo da atividade eletroquímica da reação de oxidação do glicerol

Pós-graduação em Ciência e Tecnologia de Materiais - FC

O efeito da ordenação e estrutura geométrica dos materiais PtSn/C e PdSn/C na eletrooxidação do glicerol em meio alcalino

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)