Página 1 dos resultados de 38 itens digitais encontrados em 0.010 segundos

‣ Carbon-dispersed Pt-Rh nanoparticles for ethanol electro-oxidation. Effect of the crystallite size and of temperature

LIMA, F. H. B.; PROFETI, D.; LIZCANO-VALBUENA, W. H.; TICIANELLI, E. A.; GONZALEZ, E. R.
Fonte: ELSEVIER SCIENCE SA Publicador: ELSEVIER SCIENCE SA
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
50.075137%
This work presents results of studies of carbon-dispersed Pt-Rh (1:1) nanoparticles as electrocatalysts for the ethanol electro-oxidation. The influences of the crystallite size and the cell temperature on the yields of CO2, acetaldehyde and acetic acid are investigated. Metal nanoparticles were prepared by two different routes: (1) impregnation on carbon powder followed by thermal reduction on hydrogen atmosphere and (2) chemical reduction of the precursor salts. The surface active area and the electrochemical activity of the electrocatalysts were estimated by CO stripping and cyclic voltammetry in the absence and in the presence of ethanol, respectively. Reaction intermediates and products were analyzed by in situ Fourier Transform Infra-Red Spectroscopy (FTIR) and Differential Electrochemical Mass Spectrometry (DEMS). The electrochemical stripping of CO and the electrochemical ethanol oxidation were slightly faster on the Pt-Rh electrocatalysts compared to Pt/C. Also, in situ FTIR spectra and DEMS measurements evidenced that the CO2/acetaldehyde and the CO2/acetic acid ratios are higher for the Pt-Rh/C materials in relation to Pt/C. This was ascribed to the activation of the C-C bond breaking by Rh, this being more prominent for the materials with smaller crystallite sizes. (C) 2008 Elsevier B.V. All rights reserved.

‣ Electrocatalysis of ethanol oxidation on Pt monolayers deposited on carbon-supported Ru and Rh nanoparticles

LIMA, F. H. B.; GONZALEZ, E. R.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
49.96352%
Pt monolayers deposited on carbon- supported Ru and Rh nanoparticles were investigated as electrocatalysts for ethanol oxidation. Electronic features of the Pt monolayers were studied by in situ XANES (X-ray absorption near-edge structure). The electrochemical activity was investigated by cyclic voltammetry and cronoamperometric experiments. Spectroscopic and electrochemical results were compared to those obtained on carbon-supported Pt-Ru and Pt-Rh alloys, and Pt E-TEK. XAS results indicate a modification of the Pt 5d band due to geometric and electronic interactions with the Ru ant Rh substrates, but the effect of withdrawing electrons from Pt is less pronounced in relation to that for the corresponding alloys. Electrochemical stripping of adsorbed CO, which is one of the intermediates, and the currents for the oxidation of ethanol show faster kinetics on the Pt monolayer deposited on Ru nanoparticles, and an activity that exceeds that of conventional catalysts with much larger amounts of platinum. (c) 2007 Elsevier B.V. All rights reserved.

‣ Ethanol electro-oxidation on carbon-supported Pt-Ru, Pt-Rh and Pt-Ru-Rh nanoparticles

LIMA, F. H. B.; GONZALEZ, E. R.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
60.630356%
This work investigates the effects of carbon-supported Pt, Pt-Ru, Pt-Rh and Pt-Ru-Rh alloy electrocatalysts oil the yields of CO2 and acetic acid as electro-oxidation products of ethanol. Electronic and structural features of these metal alloys were studied by in situ X-ray absorption spectroscopy (XAS). The electrochemical activity was investigated by polarization experiments and the reaction intermediates and products were analyzed by in situ Fourier Transform Infra-Red Spectroscopy (FTIR). Electrochemical stripping of CO. which is one of the adsorbed intermediates, presented a faster oxidation kinetics on the Pt-Ru electrocatalyst, and similar rates of reaction on Pt-Rh and Pt. The electrochemical current of ethanol oxidation showed a higher value and the onset potential was less positive oil Pt-Ru. However, in situ FTIR spectra evidenced that the CO2/acetic acid ratio is higher for the materials with Rh, mainly at lower potentials. These results indicate that the Ru atoms act mainly by providing oxygenated species for the oxidation of ethanol intermediates, and point out ail important role of Rh on the C-C bond dissociation. (C) 2007 Elsevier Ltd. All rights reserved.

‣ Potential oscillations in a proton exchange membrane fuel cell with a Pd-Pt/C anode

LOPES, Pietro P.; TICIANELLI, Edson A.; VARELA, Hamilton
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
48.94494%
We report in this paper the occurrence of potential oscillations in a proton exchange membrane fuel cell (PEMFC) with a Pd-Pt/C anode, fed with H(2)/100 ppm CO, and operated at 30 degrees C. We demonstrate that the use of Pd-Pt/C anode enables the emergence of dynamic instabilities in a PEMFC. Oscillations are characterized by the presence of very high oscillation amplitude, ca. 0.8 V. which is almost twice that observed in a PEMFC with a Pt-Ru/C anode under similar conditions. The effects of the H(2)/CO flow rate and cell current density on the oscillatory dynamics were investigated and the mechanism rationalized in terms of the CO oxidation and adsorption processes. We also discuss the fundamental aspects concerning the operation of a PEMFC under oscillatory regime in terms of the benefit resulting from the higher average power output. (c) 2010 Elsevier B.V. All rights reserved.; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[2009/07629-6]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[2008/10529-0]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Conselho Nacional de Pesquisa (CNPq)

‣ Ethanol oxidation reaction on PtCeO(2)/C electrocatalysts prepared by the polymeric precursor method

SOUZA, R. F. B. De; FLAUSINO, A. E. A.; RASCIO, D. C.; OLIVEIRA, R. T. S.; TEIXEIRA NETO, E.; CALEGARO, M. L.; SANTOS, M. C.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
49.237676%
This paper presents a study of the electrocatalysis of ethanol oxidation reactions in an acidic medium on Pt-CeO(2)/C (20 wt.% of Pt-CeO(2) on carbon XC-72R), prepared in different mass ratios by the polymeric precursor method. The mass ratios between Pt and CeO(2) (3:1, 2:1, 1:1, 1:2, 1:3) were confirmed by Energy Dispersive X-ray Analysis (EDAX). X-ray diffraction (XRD) structural characterization data shows that the Pt-CeO(2)/C catalysts are composed of nanosized polycrystalline non-alloyed deposits, from which reflections corresponding to the fcc (Pt) and fluorite (CeO(2)) structures were clearly observed. The mean crystallite sizes calculated from XRD data revealed that, independent of the mass ratio, a value close to 3 nm was obtained for the CeO(2) particles. For Pt, the mean crystallite sizes were dependent on the ratio of this metal in the catalysts. Low platinum ratios resulted in small crystallites. and high Pt proportions resulted in larger crystallites. The size distributions of the catalysts particles, determined by XRD, were confirmed by Transmission Electron Microscope (TEM) imaging. Cyclic voltammetry and chronoamperometic experiments were used to evaluate the electrocatalytic performance of the different materials. In all cases...

‣ Carbon supported electrocatalysts prepared by the sol-gel method and their utilization for the oxidation of methanol in acid media

SUFFREDINI, Hugo B.; SALAZAR-BANDA, Giancarlo R.; AVACA, Luis A.
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
50.045454%
One of the key objectives in fuel-cell technology is to improve the performance of the anode catalyst for the alcohol oxidation and reduce Pt loading. Here, we show the use of six different electrocatalysts synthesized by the sol -gel method on carbon powder to promote the oxidation of methanol in acid media. The catalysts Pt-PbO(x) and Pt-(RuO(2)-PbO(x)) with 10% of catalyst load exhibited significantly enhanced catalytic activity toward the methanol oxidation reaction as compared to Pt-(RuO(2))/C and Pt/C electrodes. Cyclic voltammetry studies showed that the electrocatalysts Pt-PbO(x)/C and Pt-(RuO(2)-PbO(x))/C started the oxidation process at extremely low potentials and that they represent a good novelty to oxidize methanol. Furthermore, quasi-stationary polarization experiments and cronoamperometry studies showed the good performance of the Pt-PbO(x), Pt-(RuO(2)-PbO(x))/C and Pt-(RuO(2)-IrO(2))/C catalysts during the oxidation process. Thus, the addition of metallic Pt and PbO(x) onto high-area carbon powder, by the sol -gel route, constitutes an interesting way to prepare anodes with high catalytic activity for further applications in direct methanol fuel cell systems.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP[01/14320-0]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP[06/50692-2]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP[07/05155-1]; CNPq; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CAPES; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

‣ Direct ethanol fuel cell: Electrochemical performance at 90 degrees C on Pt and PtSn/C electrocatalysts

Purgato, F. L. S.; Pronier, S.; Olivi, P.; Andrade, A. R. de; Leger, J. M.; Tremiliosi Filho, Germano; Kokoh, K. B.
Fonte: ELSEVIER SCIENCE BV; AMSTERDAM Publicador: ELSEVIER SCIENCE BV; AMSTERDAM
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
59.899385%
Carbon-supported Pt-based electrocatalysts were synthesized by Pechini method for the ethanol oxidation (EOR). Physicochemical characterizations were helpful to estimate the diameters of the obtained materials ranging from 2 nm to 5 nm. Main electrochemical experiments were carried out at 90 degrees C i.e. under the working conditions of performing the single 5 cm(2) direct ethanol fuel cell (DEFC). Pt(80)Sn(20)/C was the anode catalyst which has given the highest power density of 37 mW cm(-2). Importantly, the IR spectroscopy measurements associated with the qualitative analysis done at the output of the anodic compartment of the fuel cell have shown that ethanol oxidation on Pt(80)Sn(20)/C was mainly a two-electron sustainable process. (C) 2011 Elsevier B.V. All rights reserved.; CAPES/COFECUB [498/05]; CAPESCOFECUB; CAPES; CAPES [0509078]

‣ Development of Plurimetallic Electrocatalysts Prepared by Decomposition of Polymeric Precursors for EtOH/O-2 Fuel Cell

Palma, Livia M.; Almeida, Thiago S.; de Andrade, Adalgisa R.
Fonte: SOC BRASILEIRA QUIMICA; SAO PAULO Publicador: SOC BRASILEIRA QUIMICA; SAO PAULO
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
60.47347%
This work aimed to develop plurimetallic electrocatalysts composed of Pt, Ru, Ni, and Sn supported on C by decomposition of polymeric precursors (DPP), at a constant metal: carbon ratio of 40:60 wt.%, for application in direct ethanol fuel cell (DEFC). The obtained nanoparticles were physico-chemically characterized by X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). XRD results revealed a face-centered cubic crystalline Pt with evidence that Ni, Ru, and Sn atoms were incorporated into the Pt structure. Electrochemical characterization of the nanoparticles was accomplished by cyclic voltammetry (CV) and chronoamperometry (CA) in slightly acidic medium (0.05 mol L-1 H2SO4), in the absence and presence of ethanol. Addition of Sn to PtRuNi/C catalysts significantly shifted the ethanol and CO onset potentials toward lower values, thus increasing the catalytic activity, especially for the quaternary composition Pt64Sn15Ru13Ni8/C. Electrolysis of ethanol solutions at 0.4 V vs. RHE allowed determination of acetaldehyde and acetic acid as the main reaction products. The presence of Ru in alloys promoted formation of acetic acid as the main product of ethanol oxidation. The Pt64Sn15Ru13Ni8/C catalyst displayed the best performance for DEFC.; CAPES; CAPES; FAPESP; FAPESP; CNPq; CNPq

‣ "Preparação de eletrocatalisadores PtRu/C utilizando radiação Gama para aplicação como ânodo na oxidação direta de metanol" ; PREPARATION OF PtRu/C ANODE ELECTROCATALYSTS USING GAMMA RADIATION FOR METHANOL ELECTRO-OXIDATION

Silva, Dionisio Furtunato da
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 18/04/2006 Português
Relevância na Pesquisa
51.18501%
Foram preparados eletrocatalisadores PtRu/C (nanopartículas PtRu suportadas em carbono) utilizando processos radiolíticos (radiação gama) e testados na oxidação direta na oxidação direta de metanol. Neste procedimento submeteu-se à radiação gama, sob agitação, soluções de água/2-propanol e água/etileno glicol, ambas contendo íons dos metais precursores e o suporte de carbono. Foram variadas as razões volumétricas água/2-propanol e água/etileno glicol e a dose de radiação total recebida (kGy). A razão atômica nominal Pt:Ru utilizada em todos os experimentos foi de 50:50. Os eletrocatalisadores obtidos foram caracterizados por análise de raios X por energia dispersiva (EDX), por difração de raios X (DRX), por microscopia eletrônica de transmissão (MET) e por voltametria cíclica (VC). A eletro-oxidação do metanol foi estudada por voltametria cíclica (VC) utilizando a técnica do eletrodo de camada fina porosa. Os eletrocatalisadores preparados no meio reacional água/2-propanol apresentaram tamanho de cristalito na faixa de 3 - 5 nm e razão atômica Pt:Ru de 50:50. Os eletrocatalisadores preparados em água/etileno glicol apresentaram tamanho de cristalito na faixa de 2 - 3 nm, menores que os obtidos em água/2-propanol...

‣ Eletrocatalisadores de ligas de platina dispersos em substratos de óxidos para a reação de oxidação de hidrogênio puro e na presença de CO; Electrocatalysts of platinum alloys dispersed in oxide substrates for pure hydrogen oxidation reaction and in the presence of CO

Freitas, Kênia da Silva
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 29/04/2009 Português
Relevância na Pesquisa
40.478145%
Neste trabalho são apresentados resultados dos estudos da reação de oxidação de hidrogênio puro realizados em eletrodos rotatório em camada ultrafina porosa e na presença de CO em células a combustível utilizando catalisadores formados por Pt dispersas em substratos de óxidos, tais como, Pt/RuO 2 -C, Pt/RhO 2 -C, Pt/WO 3 -C e em Pt/WC-C. As reações foram também estudadas em suporte puro, como, RhO 2 /C e WC/C em diferentes proporções atômicas. Este estudo teve como finalidade estudar as propriedades catalíticas destes materiais visando elucidar os mecanismos da reação de oxidação de hidrogênio (ROH) sobre estes catalisadores dispersos, possibilitando a obtenção de parâmetros cinéticos das reações. Em conjunto com as medidas eletroquímicas, foram realizados estudos sobre as propriedades eletrônicas e estruturais destes catalisadores, o que possibilita relacionar suas propriedades eletrônicas e estruturais com a cinética da HOR. Observou-se que a presença dos óxidos de Ru, Rh e WO 3 favorecem a diminuição do grau de recobrimento da Pt por CO, deixando mais sítios disponíveis a ROH, em consequência do esvaziamento da banda 5d da Pt, o que diminui a retro-doação de elétrons da Pt ao CO, diminuindo a força da ligação Pt-CO. Como observado...

‣ Preparação de eletrocatalisadores PtRu/C e PtSn/C utilizando feixe de elétrons para aplicação como anodo na oxidação  direta de metanol e etanol em células a combustível de baixa temperatura; Preparation of PtRu/C e PtSn/C eletrocatalysts using electron beam irradiaton for direct methanol and ethanol fuel cell

Silva, Dionisio Furtunato da
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 24/11/2009 Português
Relevância na Pesquisa
41.350664%
Foram preparados eletrocatalisadores PtRu/C e PtSn/C utilizando feixe de elétrons para a redução dos íons metálicos em solução. Neste procedimento submeteu-se ao feixe de elétrons, sob agitação, soluções de água/etileno glicol (EG) e água/2- propanol, ambas contendo íons dos metais precursores e o suporte de carbono. Foram variadas as razões volumétricas água/2-propanol e água/etileno glicol, a razão atômica entre os metais, o tempo de irradiação e a taxa de dose. Os eletrocatalisadores obtidos foram caracterizados por análise de raios X por energia dispersiva (EDX), por difração de raios X (DRX), por voltametria cíclica (VC) e por espectroscopia Mössbauer. A atividade destes eletrocatalisadores na oxidação eletroquímica do metanol e do etanol foi avaliada por voltametria cíclica e cronoamperometria, utilizando a técnica do eletrodo de camada fina porosa, e pelas curvas de polarização obtidas em células a combustível unitárias operando diretamente com metanol e etanol. Os eletrocatalisadores PtRu/C preparados no meio reacional água/etileno glicol(EG) apresentaram razões atômicas diferentes das razões atômicas nominais. Os resultados sugerem que parte dos íons Ru(III) presentes no meio reacional não foram reduzidos. Os materiais obtidos apresentaram a fase cúbica de face centrada (cfc) da Pt e suas ligas e tamanhos de cristalito na faixa de 2 a 3 nm. Os eletrocatalisadores PtRu/C preparados em água/2- propanol apresentaram razões atômicas Pt:Ru similares às razões nominais. Os materiais obtidos apresentaram as fases cfc da platina e suas ligas e tamanhos de cristalito entre 3 e 4 nm. Os eletrocatalisadores PtSn/C preparados no meio reacional água/EG e água/2-propanol apresentaram razões atômicas Pt:Sn similares às razões nominais. Os materiais obtidos apresentaram as fases cfc da platina com tamanho de cristalitos na faixa de 2 a 4 nm e SnO2 (cassiterita). Os estudos sobre a oxidação eletroquímica de metanol e etanol mostraram que foi possível obter materiais com atividades similares e/ou superiores às atividades dos eletrocatalisadores comerciais PtRu/C (E-TEK) e PtSn/C (BASF)...

‣ Preparação de eletrocatalisadores PtRuNi/C pelo método da redução por álcool para  aplicação como ânodo na oxidação direta de metanol em células a combustível de eletrolito polimérico sólido; Preparation of PtRuNi/C eletrocatalysts prepared by an alcohol reduction process for methanol electro-oxidation in Direct Methanol Fuel Cell

Ribeiro, Vilmaria Aparecida
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 20/06/2008 Português
Relevância na Pesquisa
41.354585%
Foi estudada a preparação de eletrocatalisadores PtRuNi/C (nanopartículas PtRuNi suportadas em carbono) pelo método da redução por álcool utilizando H2PtCl6.6H20, RuCl3.1,5H2O e NiCI2.6H2O como fonte de metais, etileno glicol como solvente e agente redutor e Carbón Vulcan XC72R como suporte. Os eletrocatalisadores obtidos foram caracterizados por análise de raios X por energia dispersiva (EDX), difração de raios X (XRD), microscopía eletrônica de transmissão (TEM) e voltametria cíclica (CV). A eletro-oxidação do metanol foi estudada por voltametria cíclica e cronoamperometria visando aplicação em células a combustível a metanol direto (DMFC). Inicialmente, os eletrocatalisadores PtRuNi/C (20% em massa de metais) foram preparados com uma razão atômica Pt:Ru:Ni de 50:40:10 em meio ácido e em meio alcalino (razão molar OHVmetais = 8) sendo que, neste caso, uma solução de KOH 1 mol L-1 foi adicionada ao meio reacional na proporção desejada. Para o material preparado em meio ácido foi observado apenas a redução dos íons Pt(IV) e Ru(lll), enquanto que os íons Ni(ll) permaneceram em solução. A redução dos íons Ni(ll) e sua incorporação nas nanopartículas metálicas ocorreu somente em meio alcalino. Neste caso observou-se uma estrutura cúbica de face centrada característica de Pt e suas ligas e também um menor tamanho de cristalito. Por outro lado...

‣ Pt-Ru Catalysts supported on mesoporous carbons for polymer electrolyte membrane fuel cells

Calderon, J. C.; Figueiredo, J. L.; Mahata, N.; Pereira, M. F. R.; Fernandes, Vitor R.; Rangel, C. M.; Pastor, E.; Calvillo, L.; Lázaro, M. J.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em 19/04/2010 Português
Relevância na Pesquisa
90.34216%
Pt-Ru electrocatalysts supported on xerogels and CMK-3 ordered mesoporous carbons were synthesized by reduction with formate ions (SFM method). Some of the carbon supports were chemically treated with HNO3 in order to generate oxygen groups on the surface, while other supports were heat treated. Physical characterization of the catalyst was obtained using X-ray dispersive energy (EDX) and X-ray diffraction (XRD) techniques. Results showed that Pt-Ru catalysts with similar metal content (20%) and atomic ratios (Pt:Ru 1:1) were obtained. The electrochemical activity was studied by cyclic voltammetry and chronoamperometry. Higher methanol oxidation current densities were found for catalyst deposited on chemically treated supports. Electrode preparation and MEA assembly allowed an in-house built direct methanol fuel to be fitted with the synthesized catalysts and supports in order to assess their performance. Cell and reactants were conditioned by a direct methanol test station. Polarisation curves were measured and confirmed data obtained by voltammetry, regarding the effect of heat treatment of the carbon support. Normalised power curves per weight of catalyst are discussed in terms of the significant impact on noble metal loading and attained cell maximum power...

‣ Influence of the support characteristics and their functionalization on the catalytic activity of Pt-Ru catalysts for PEM fuel cells

Calderon, J. C.; Figueiredo, J. L.; Mahata, N.; Pereira, M. F. R.; Fernandes, Vitor R.; Rangel, C. M.; Pastor, E.; Calvillo, L.; Lázaro, M. J.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em 27/06/2011 Português
Relevância na Pesquisa
59.044756%

‣ Influence of catalyst support characteristics and functionalization on the catalytic activity of Pt-Ru for PEM fuel cells

Calderon, J. C.; Figueiredo, J. L.; Mahata, N.; Pereira, M. F. R.; Fernandes, Vitor R.; Rangel, C. M.; Calvillo, L.; Lázaro, M. J.; Pastor, E.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Artigo de Revista Científica
Publicado em //2011 Português
Relevância na Pesquisa
90.39398%
Pt-Ru electrocatalysts supported on carbon xerogels and ordered mesoporous carbons were synthesized by reduction with formate ions (SFM method). Chemical and heat treatments were applied to modified the surface chemistry of original carbon supports. Physical characterization of the catalysts was performed using X-ray dispersive energy (EDX) and X-ray diffraction (XRD) techniques, while the electrochemical activity towards methanol oxidation was studied by cyclic voltammetry (CV). Pt-Ru catalysts with nominal metal content (20 wt.%) and atomic ratios (Pt:Ru 1:1) were successfully synthesized on the different supports. Higher methanol oxidation current densities were obtained for those supports with a higher content of surface oxygen groups. Gas diffusion electrode and membrane-electrode-assembly preparation allowed an in-house built of a direct methanol fuel monocell for the evaluation of the catalysts performance. Polarization curves were measured confirming the results obtained in a three electrodes electrochemical cell by CV. Normalized power curves per weight of Pt are discussed in terms of the significant impact on noble metal loading and attained cell maximum power, in comparison with results obtained with a commercial catalyst.

‣ Influence of catalyst support characteristics and functionalization on the catalytic activity of Pt-Ru for PEM fuel cells

Calderon, J. C.; Figueiredo, J. L.; Mahata, N.; Pereira, M. F. R.; Fernandes, Vitor R.; Rangel, C. M.; Calvillo, L.; Lázaro, M. J.; Pastor, E.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Artigo de Revista Científica
Publicado em //2011 Português
Relevância na Pesquisa
90.39398%
Pt-Ru electrocatalysts supported on carbon xerogels and ordered mesoporous carbons were synthesized by reduction with formate ions (SFM method). Chemical and heat treatments were applied to modified the surface chemistry of original carbon supports. Physical characterization of the catalysts was performed using X-ray dispersive energy (EDX) and X-ray diffraction (XRD) techniques, while the electrochemical activity towards methanol oxidation was studied by cyclic voltammetry (CV). Pt-Ru catalysts with nominal metal content (20 wt.%) and atomic ratios (Pt:Ru 1:1) were successfully synthesized on the different supports. Higher methanol oxidation current densities were obtained for those supports with a higher content of surface oxygen groups. Gas diffusion electrode and membrane-electrode-assembly preparation allowed an in-house built of a direct methanol fuel monocell for the evaluation of the catalysts performance. Polarization curves were measured confirming the results obtained in a three electrodes electrochemical cell by CV. Normalized power curves per weight of Pt are discussed in terms of the significant impact on noble metal loading and attained cell maximum power, in comparison with results obtained with a commercial catalyst

‣ Carbon monoxide oxidation on Pt-Ru electrocatalysts supported on high surface area carbon

Colmati Jr.,Flavio; Lizcano-Valbuena,William H.; Camara,Giuseppe A.; Ticianelli,Edson A.; Gonzalez,Ernesto R.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2002 Português
Relevância na Pesquisa
79.796914%
This work describes the preparation and characterization of Pt-Ru alloys dispersed on high surface area carbon, which were evaluated for CO oxidation on thin porous coating rotating disk electrodes and for hydrogen oxidation on polymer electrolyte fuel cells fed with hydrogen containing 100 ppm CO. A thermal treatment (H2, 300 ºC) applied to the catalysts improves the tolerance to small quantities of CO and, in some cases, reduces the potential necessary to promote the CO oxidation during a linear potential scan. Under operational conditions in a fuel cell in the presence of CO it was observed that the best results were obtained when the Pt-Ru/C alloy was prepared by simultaneous reduction of the ions Pt (IV) and Ru (III), as opposed to a sequential reduction.

‣ Electrochemical behaviour of ionic liquid functionalized carbon supported Pt-Ru catalysts 

Esteves, M. Alexandra; Sá, A. I. Correia de; Rangel, C. M.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 Português
Relevância na Pesquisa
79.414863%
Ionic liquid (IL) functionalized carbon supported nanocatalysts, including platinum-ruthenium catalysts, have been under investigation to achieve better catalytic performance on polymer electrolyte membrane fuel cells. Ionic liquids have particular physical properties, which usually improve the stabillity and dispersion of metal nanosized particles, providing an increase of the electrochemical active surface area. In this work, the synthesis and the electrochemical behaviour of two new ionic liquid functionalizated carbon supported Pt-Ru nanocatalysts is investigated regarding the methanol oxidation reaction. Preliminary obtained results show that IL functionalization of carbon can produce supported catalysts with improved performances depending on the ionic liquid and on the reduction process used to produce the catalyst nanosized particles.

‣ Co-catalytic effect of nickel in Pt-Ru/C and Pt-Sn/C electrocatalysts for ethanol electrooxidation

Ribadeneira,R. E.; Hoyos,B. A.
Fonte: Latin American applied research Publicador: Latin American applied research
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2010 Português
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In the present study, we examined the effect of adding nickel to Pt-Ru and Pt-Sn catalysts for ethanol electrooxidation. The alcohol-reduction process with ethylene glycol was used to prepare ten electrocatalysts. These were microchemically and physically characterized by EDX and XRD analysis. The electrocatalysts were evaluated at mini-electrodes with cyclic voltammetry at 25 and 50 °C in sulfuric acid and ethanol solutions, and as anodes in fuel cell tests. Nickel addition to Pt-Ru mixtures significantly increased the catalytic activity toward ethanol electrooxidation. For Pt-Ru-Ni catalysts, the current density was around five times greater than all other investigated mixtures. Nickel also duplicated the catalytic activity of the Pt-Sn catalyst. Furthermore ethanol electrooxidation increased with temperature for most catalytic mixtures, and the electrocatalytic activity of mixtures containing nickel, demonstrate a considerable increase with temperature. Pt-Ru-Ni catalytic activity was higher than that of all other investigated mixtures. The fuel cell test demonstrated that the addition of nickel to Pt-Ru and Pt-Sn catalysts enhances the performance of the DEFC.

‣ Bi and Three-Metallic Electrocatalysts Preparation for Methanol Oxidation

Márquez-Navarro,Yara; Galicia,Laura; Lara,Víctor Hugo; Ángel,Gloria Del
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2008 Português
Relevância na Pesquisa
59.52081%
Bi and tri-metallic (Pt-Ru/C, Pt-Mo/C and Pt-Ru-Mo/C) catalysts were synthesized by using as precursors the metallic salts and applying the co-impregnation method. The tri-metallic catalysts underwent different thermal treatments and they were characterized by X-Ray. The catalytic activity for methanol oxidation reaction was determined by cyclic voltammetry (CV). The results show that the materials calcined before reduction presented the highest catalytic activity for methanol oxidation reaction.