Electrocatalysis of oxidation of hydrogen on platinum ordered intermetallic phases: Kinetic and mechanistic studies

An experimentally based kinetic and mechanistic study of the hydrogen oxidation reaction (HOR) on platinum and platinum ordered intermetallic materials in acid medium is presented. RDE kinetic data were re-evaluated and complemented by Tafel plots obtained from chronoamperometric measurements. Among the materials evaluated, PtSb and PtSn exhibited markedly improved kinetic current densities and exchange current densities, compared to Pt in the same experimental conditions. It is proposed that the intermetallic phase enhanced the adsorptive characteristic of the surface sites and, as a consequence, improved the kinetics of the adsorption steps (Tafel or Heyrovsky) of the mechanism involved. (c) 2006 Published by Elsevier B.V.

Hydrogen oxidation on ordered intermetallic phases of platinum and tin - A combined experimental and theoretical study

Hydrogen oxidation on the surfaces of the intermetallic compounds Pt 3Sn, PtSn and PtSn2 has been studied by the rotating disc electrode technique. Pt3Sn and PtSn were found to be good catalysts, about as good as Pt, while PtSn2 was inactive over the investigated range of potentials. Underpotential deposition of hydrogen is observed only on Pt3Sn. These results are explained by theoretical calculations based on a theory developed within our own group, and by density functional theory. © 2012 Elsevier B.V.

Preparation and characterization of ordered intermetallic platinum phases for electrocatalytic applications

Ordered intermetallic phases of Pt with several transition metals have been prepared and their electrocatalytic properties studied. In light of these tests it is proposed that these catalysts could be used as electrodes in fuel cells, as they combine an excellent capacity to adsorb organic fuels at the Pt sites with low susceptibility to being poisoned by intermediates and reaction products at the transition-metal sites. An experimental procedure used to obtain the four intermetallic phases Pt-M (M = Mn, Pb, Sb and Sn) is described. The phases thus produced were characterized by X-ray diffraction, scanning electron microscopy with surface analysis by energy-dispersive X-ray spectrometry, scanning tunneling microscopy and X-ray photoelectron spectroscopy. The data thus obtained support the conclusion that the method described here is highly effective for the preparation of Pt-M phases featuring a range of structural and electronic modifications that will allow a useful relation to be established between their physicochemical properties and predicted electrocatalytic activity. (C) 2007 Elsevier Ltd. All rights reserved.

Hydrogen oxidation on ordered intermetallic electrodes covered with CO

This describes an experimental evaluation of the electrocatalytic activity of the hydrogen oxidation reaction on electrodes of platinum and the ordered intermetallic phases PtSb and PtSn, on which CO has previously been deposited. The experiments were carried out in perchloric acid solution and the analysis based on steady-state polarization curves and Tafel plots derived from chronoamperometric data. Both intermetallics, PtSb and PtSn, performed better than Pt towards the HOR, when their surface was deliberately covered with CO. It is suggested that the intermetallic surfaces have a lower affinity for CO molecules, causing a lower CO coverage on these surfaces, and/or a weaker surface-CO interaction, compared to Pt under the same conditions. (C) 2007 Elsevier B.V. All rights reserved.

Estudo da eletrocatálise da reação de oxidação de etanol sobre fases intermetálicas ordenadas Pt-M (M = Mn,Mo, Pb, Sb e Sn)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estudo da eletrocatálise da reação de oxidação do glicerol sobre as fases intermetálicas ordenadas PtSn e AuSn

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da eletrocatálise das reações de oxidação de ácido fórmico e metanol sobre fases intermetálicas ordenadas Pt-M(M = Mn, Mo, Pb, Sb e Sn)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese, caracterização e avaliação eletroquímica de nanopartículas intermetálicas ordenadas PtSb e PtSn

Pós-graduação em Ciência e Tecnologia de Materiais - FC

A teoria do funcional da densidade na caracterização de fases intermetálicas ordenadas

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

Estudo teórico das reações de hidrogênio e do monóxido de carbono sobre fases intermetálicas

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

Metodologia computacional baseada em DFT, para compreensão de processos eletródicos em fases intermetálicas ordenadas

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Estudo da adsorção e oxidação do monóxido de carbono sobre as fases intermetálicas ordenadas AuIn, AuSb2, AuSn, PdSb e PdSn

Aiming to reduce the cost of electrocatalysts and a greater resistance to CO poisoning this work was to study the adsorption and oxidation of carbon monoxide on ordered intermetallic phases AuIn, AuSb2, AuSn, PdSb and PdSn using voltammetric techniques in alkaline electrolyte solution. The results suggest that the AuSn and PdSn intermetallics has some form of resistance to CO poisoning. It is assumed that this behavior is a result of electronic effect and the effect of the third body has been achieved by adding a second metal to Au and Pd. However, further studies should be conducted to confirm this hypothesis as to test these materials as electrocatalysts in the reaction of oxidation of fuels

On the existence of ordered phases of encapsulated diamondoids into carbon nanotubes

We have investigated some diamondoids encapsulation into single walled carbon nanotubes (with diameters ranging from1.0 up to 2.2 nm) using fully atomistic molecular dynamics simulations. Diamondoids are the smallest hydrogen-terminated nanosized diamond-like molecules. Diamondois have been investigated for a large class of applications, ranging from oil industry to pharmaceuticals. Molecular ordered phases were observed for the encapsulation of adamantane, diamantane, and dihydroxy diamantanes. Chiral ordered phases, such as; double, triple, 4- and 5-stranded helices were also observed for those diamondoids. Our results also indicate that the modification of diamondoids through chemical functionalization with hydroxyl groups can lead to an enhancement of the molecular packing inside the carbon nanotubes in comparison to non-functionalized molecules. For larger diamondoids (such as, adamantane tetramers), we have not observed long-range ordering, but only a tendency of incomplete helical structural formation. © 2012 Materials Research Society.

Ordered phases in the extended Hubbard model

A novel method to probe the diverse phases for the extended Hubbard model (EHM), including the correlated hopping term, is presented. We extend an effective medium approach [1] to a bipartite lattice, allowing for charge- and/or spin-ordered phases. We calculate the necessary correlation functions to build the EHM phase diagram.

Synthesis and Characterization of Ordered Intermetallic Nanostructured PtSn/C and PtSb/C and Evaluation as Electrodes for Alcohol Oxidation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)