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‣ Electrocatalytic oxidation of methanol by the [Ru3O(OAc)6(py)2(CH3OH)]3+cluster: improving the metal-ligand electron transfer by accessing the higher oxidation states of a multicentered system

TOMA, Henrique E.; ARAKI, Koiti; FORMIGA, André Luiz Barboza; ALEXIOU, Anamaria D. P.; NUNES, Genebaldo S.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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The [Ru3O(Ac)6(py)2(CH3OH)]+ cluster provides an effective electrocatalytic species for the oxidation of methanol under mild conditions. This complex exhibits characteristic electrochemical waves at -1.02, 0.15 and 1.18 V, associated with the Ru3III,II,II/Ru3III,III,II/Ru 3III,III,III /Ru3IV,III,III successive redox couples, respectively. Above 1.7 V, formation of two RuIV centers enhances the 2-electron oxidation of the methanol ligand yielding formaldehyde, in agreement with the theoretical evolution of the HOMO levels as a function of the oxidation states. This work illustrates an important strategy to improve the efficiency of the oxidation catalysis, by using a multicentered redox catalyst and accessing its multiple higher oxidation states.; FAPESP; CNPq; Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)

‣ Nanogravimetric and voltammetric studies of a Pt-Rh alloy surface and its behavior for methanol oxidation

OLIVEIRA, R. T. S.; SANTOS, M. C.; NASCENTE, P. A. P.; BULHOES, L. O. S.; PEREIRA, E. C.
Fonte: ELECTROCHEMICAL SCIENCE GROUP Publicador: ELECTROCHEMICAL SCIENCE GROUP
Tipo: Artigo de Revista Científica
Português
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This paper describes the preparation of a Pt-Rh alloy surface electrodeposited on Pt electrodes and its electrocatalytic characterization for methanol oxidation. The X-ray photoelectronic spectroscopy ( XPS) results demonstrate that the surface composition is approximately 24 at-% Rh and 76 % Pt. The cyclic voltammetry (CV) and electrochemical quartz crystal (EQCN) results for the alloy were associated, for platinum, to the well known profile in acidic medium. For Rh, on the alloy, the generation of rhodium hydroxide species (Rh(OH)(3) and RhO(OH)(3)) was measured. During the successive oxidation-reduction cycles the mass returns to its original value, indicating the reversibility of the processes. It was not observed rhodium dissolution during the cycling. The 76/24 at % Pt-Rh alloy presented singular electrocatalytic activity for methanol electrooxidation, which started at more negative potentials compared to pure Pt (70 mV). During the sweep towards more negative potentials, there is only weak CO re-adsorption on both Rh and Pt-Rh alloy surfaces, which can be explained by considering the interaction energy between Rh and CO.

‣ On-line mass spectrometry of the electro-oxidation of methanol in acidic media on tungsten carbide

ANGELUCCI, Camilo A.; DEINER, L. Jay; NART, Francisco C.
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
48.204863%
The electro-oxidation of methanol at supported tungsten carbide (WC) nanoparticles in sulfuric acid solution was studied using cyclic voltammetry, potentiostatic measurements, and differential electrochemical mass spectroscopy (DEMS). The catalyst was prepared by a sonochemical method and characterized by X-ray diffraction. Over the WC catalyst, the oxidation of methanol (1 M in a sulfuric acid electrolyte) begins at a potential below 0.5 V/RHE during the anodic sweep. During potentiostatic measurements, a maximum current of 0.8 mA mg(-1) was obtained at 0.4 V. Measurements of DEMS showed that the methanol oxidation reaction over tungsten carbide produces CO2 (m/z=44); no methylformate (m/z=60) was detected. These results are discussed in the context of the continued search for alternative materials for the anode catalyst of direct methanol fuel cells.; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)[04/03051-6]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Cientfico e Tecnologico (CNPq); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

‣ Effect of the catalyst composition in the Pt-x(Ru-Ir)(1-x)/C system on the electro-oxidation of methanol in acid media

EGUILUZ, K. I. B.; SALAZAR-BANDA, G. R.; MIWA, D.; MACHADO, S. A. S.; AVACA, L. A.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
Português
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The effect of variations in the composition for ternary catalysts of the type Pt-x(Ru-Ir)(1-x)/C on the methanol oxidation reaction in acid media for x values of 0.25, 0.50 and 0.75 is reported. The catalysts were prepared by the sol-gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic absorption spectroscopy (AAS) and energy dispersive X-ray (EDX) analyses. The nanometric character (2.8-3.2 nm) of the sol-gel deposits was demonstrated by XRD and TEM while EDX and AAS analyses showed that the metallic ratio in the compounds was very near to the expected one. Cyclic voltammograms for methanol oxidation revealed that the reaction onset occur at less positive potentials in all the ternary catalysts tested here when compared to a Pt-0.75-Ru-0.25/C (E-Tek) commercial composite. Steady-state polarization experiments (Tafel plots) showed that the Pt-0.25(Ru-Ir)(0.75)/C catalyst is the more active one for methanol oxidation as revealed by the shift of the reaction onset towards lower potentials. In addition, constant potential electrolyses suggest that the addition of Ru and Ir to Pt decreases the poisoning effect of the strongly adsorbed species generated during methanol oxidation. Consequently...

‣ Synthesis, Characterization, and Electrocatalytic Activity toward Methanol Oxidation of Carbon-Supported Pt(x)-(RuO(2)-M)(1-x) Composite Ternary Catalysts (M = CeO(2), MoO(3), or PbO(x))

EGUILUZ, Katlin I. B.; MALPASS, Geoffroy R. P.; PUPO, Marilia M. S.; SALAZAR-BANDA, Giancarlo R.; AVACA, Luis A.
Fonte: AMER CHEMICAL SOC Publicador: AMER CHEMICAL SOC
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
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Carbon-supported platinum is commonly used as an anode electrocatalyst in low-temperature fuel cells fueled with methanol. The cost of Pt and the limited world supply are significant barriers for the widespread use of this type of fuel cell. Moreover, Pt used as anode material is readily poisoned by carbon monoxide produced as a byproduct of the alcohol oxidation. Although improvements in the catalytic performance for methanol oxidation were attained using Pt-Ru alloys, the state-of-the-art Pt-Ru catalyst needs further improvement because of relatively low catalytic activity and the high cost of noble Pt and Ru. For these reasons, the development of highly efficient ternary platinum-based catalysts is an important challenge. Thus, various compositions of ternary Pt(x)-(RuO(2)-M)(1-x)/C composites (M = CeO(2), MoO(3), or PbO(x)) were developed and further investigated as catalysts for the methanol electro-oxidation reaction. The characterization carried out by X-ray diffraction, energy-dispersive X-ray analysis, transmission electron microscopy, X-ray photoelectron spectroscopy, and cyclic voltammetry point out that the different metallic oxides were successfully deposited on the Pt/C, producing small and well-controlled nanoparticles in the range of 2.8-4.2 nm. Electrochemical experiments demonstrated that the Pt(0.50)(RuO(2)-CeO(2))(0.50)/C composite displays the higher catalytic activity toward the methanol oxidation reaction (lowest onset potential of 207 mV and current densities taken at 450 mV...

‣ 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
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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)

‣ "Estudos da eletroquímica do diamante dopado com boro e da sua superfície modificada com catalisadores para a oxidação de metanol e etanol"; "Studies of boron-doped diamond eletrochemistry and of their surface modified with catalyst ofr the methanol and ethanol oxidation"

Banda, Giancarlo Richard Salazar
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 22/09/2006 Português
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Este trabalho mostra estudos das propriedades eletroquímicas do eletrodo de diamante dopado com boro (DDB) e descreve a utilização de eletrodos de DDB, modificados direta ou indiretamente pelo método Sol-gel, para a oxidação de metanol e de etanol em meio ácido. Do estudo das propriedades superficiais do diamante concluiu-se que a polarização catódica é bastante apropriada para um bom desempenho do material é que não introduz diferenças estruturais detectáveis no filme de DDB, indicando que a melhora na resposta eletroquímica é devida somente a mudanças superficiais. Entretanto, polarizações catódicas consecutivas e extensivas por longos períodos de tempo produzem uma erosão da superfície do eletrodo. Adicionalmente, estudos realizados usando voltametria cíclica e espectroscopia fotoeletrônica de raios X, mostraram que a superfície de eletrodos de DDB pré-tratados catodicamente tem um comportamento eletroquímico dinâmico, apresentando uma perda da reversibilidade para o sistema Fe(CN)63-/4- em função do tempo de exposição ao ar. Isto é devido, possivelmente, à perda de hidrogênio superficial decorrente da oxidação da superfície do eletrodo pelo oxigênio do ar. Este comportamento dinâmico da superfície do DDB é inversamente dependente ao teor de boro do eletrodo. Foi observado também que a quantidade de sítios ativos disponíveis na superfície do eletrodo é diretamente proporcional à dopagem do mesmo e deve ser conseqüência da quantidade de boro superficial. Desses estudos concluiu-se que todos os eletrodos de DDB com distintas dopagens usados nesta tese (300...

‣ "Dependência da seletividade da reação de eletro-oxidação de metanol e etanol sobre nanopartículas de Pt/C e PtRh/C"; "Dependence of the selectivity of the methanol and ethanol electrooxidation reaction on Pt/C and PtRh/C nanoparticles"

Bergamaski, Kleber
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 22/12/2005 Português
Relevância na Pesquisa
48.42076%
A eletro-oxidação de metanol e etanol é um tema ativamente estudado em eletrocatálise. O motivo da grande atenção dada à investigação da atividade eletrocatalítica destes álcoois é devido à procura de novos sistemas conversores de energia mais eficientes e menos poluidores. As pesquisas em eletrocatálise têm sido direcionadas também ao estudo de sistemas nanoparticulados. Partículas metálicas de tamanho nanométrico oferecem aspectos interessantes no estudo de efeitos estruturais em eletrocatalisadores dispersos. O decréscimo do tamanho de partícula promove uma utilização mais eficiente do catalisador, uma vez que a razão do número de átomos superficiais pelo número de átomos total é favorecida. Neste trabalho, investigou-se a oxidação eletroquímica de metanol e etanol sobre catalisadores de Pt e catalisadores de PtRh através da técnica de espectrometria de massas eletroquímica diferencial (DEMS). Nos catalisadores PtRh/C foi estudado o efeito da composição atômica do catalisador na reação de oxidação destes álcoois e nos catalisadores comerciais Pt/C E-Tek o efeito de tamanho de partícula na reação de oxidação de metanol. Na eletro-oxidação dos álcoois metanol e etanol sobre os catalisadores PtRh/C observou-se que a corrente faradáica decresceu em função do aumento de ródio no catalisador bimetálico. Por outro lado...

‣ Desenvolvimento de catalisadores preparados pelo método sol-gel para a oxidação de metanol; Development of catalysts prepared by the sol-gel method for methanol oxidation

Eguiluz, Katlin Ivon Barrios
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 10/07/2008 Português
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Este trabalho descreve o desenvolvimento e caracterização de novos materiais catalíticos para a oxidação de metanol em aplicações em células a combustível de metanol direto. Os materiais foram preparados utilizando o método sol-gel pela incorporação de diversas quantidades de metais, tais como: Ru, Ir, Ce, Mo e Pb sobre amostras de pó de Pt/C da E-Tek (10% Pt). Na maioria dos casos, o compósito resultante estava formado pelos referidos óxidos metálicos como observado nas medidas de caracterização física. Os sistemas estudados incluíram as seguintes misturas binárias: (Pt0,50-(RuO2)0,50/C, Pt0,50-(IrOx)0,50/C, Pt0,50-(CeO,sub>2)0,50/C, (PtOx)0,50-(PbOx)0,50/C, Pt0,50-(Môo3)0,50/C) e as misturas ternárias: (Pt0,25(RuO2-IrOx)0,75/C, Pt0,50 (RuO2-IrOx)0,50/C, Pt0,75(RuO2-IrOx)0,25/C, Pt0,25(RuO2-CeO2)0,75/C, Pt0,50 (RuO2-CeO2)0,50/C, Pt0,75(RuO2-CeO2)0,25/C, (PtOx)0,25(RuO2- PbOx)0,75/C, (PtOx)0,50 (RuO2-PbOx)0,50/C, (PtOx)0,75(RuO2-PbOx)0,25/C, Pt0,25(RuO2- Môo3)0,75/C, Pt0,50(RuO2-MoO3)0,50/C e Pt0,75(RuO2-MoO3)0,25/C). Medidas de difratometria de raios-X, mostraram que todos os metais incorporados às amostras de Pt/C sintetizam-se como óxidos (RuO2, IrO2, Ir2O3, CeO2, Pb3O4 e MoO3), enquanto que a platina manteve-se como Pt metálica com exceção nos compósitos contendo chumbo...

‣ Effects of Alloyed and Oxide Phases on Methanol Oxidation of Pt-Ru/C Nanocatalysts of the Same Particle Size

Godoi, Denis R. M.; Perez, Joelma; Villullas, Hebe de Las Mercedes
Fonte: Amer Chemical Soc Publicador: Amer Chemical Soc
Tipo: Artigo de Revista Científica Formato: 8518-8525
Português
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Processo FAPESP: 07/54434-0; Processo FAPESP: 06/60769-2; In this work, methanol oxidation was studied on carbon-supported Pt-Ru nanocatalysts, where the amounts of alloyed and oxide phases were modified by heat treatments in different atmospheres. Because particle growth was avoided using, mild temperature conditions, the study reported here was conducted in the absence of particle size effects. All samples were characterized by X-ray diffraction and transmission electron microscopy. The general electrochemical behavior of the nanocatalysts was evaluated by cyclic voltammetry, and the electrocatalytic activity for the oxidation of methanol was studied in 0.5 mol L(-1) methanol acid solutions by linear potential sweeps and chronoamperometry. The results obtained clearly evidence that the presence of oxide species is necessary to enhance the electrocatalytic activity for methanol oxidation. Oxidation of adsorbed CO was also measured. Both reactions, methanol and adsorbed CO oxidation, were found to be very sensitive to the surface changes produced by the heat treatments. Interestingly, the best catalyst for methanol oxidation was not found to be the most efficient for the oxidation of adsorbed CO. Electrocatalytic activities correlate well with oxidation states and electronic properties analyzed by X-ray photoelectron spectroscopy and in situ dispersive X-ray absorption spectroscopy.

‣ Methanol oxidation on PtRu/C electrocatalysts prepared by a microemulsion method

Godoi, Denis R.M.; Perez, Joelma; Villullas, H. Mercedes
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 11-17
Português
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PtRu/C nanocatalysts were prepared by a microemulsion method using different values of water/surfactant molar ratio in order to get different particle sizes. Crystallite sizes and structural properties were determined by X-ray diffraction. Particle size and distribution were characterized by transmission electron microscopy and average composition was determined by energy dispersive X-ray analysis. Differential scanning calorimetry measurements indicated the presence of oxides in the as-prepared catalysts. The general electrochemical behavior was evaluated by cyclic voltammetry in 0.5 M sulfuric acid and the electrocatalytic activity towards the oxidation of methanol was studied in 0.5 M methanol acid solutions by potential sweeps and chronoamperometry. copyright The Electrochemical Society.

‣ Estudo da reação de oxidação do metanol sobre fases intermetálicas ordenadas Pt-M com a técnica de espectroscopia de impedância eletroquímica

Perez, Letícia
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Dissertação de Mestrado Formato: 102 f. : il.
Português
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Pós-graduação em Ciência e Tecnologia de Materiais - FC; A oxidação do metanol apresenta problemas acentuadamente complexos que ainda não foram satisfatoriamente solucionados. Possui um mecanismo duplo caminho, ou seja, diretamente a CO2 ou pelo caminho alternativo via intermediários. Também como intermediário/produto da reação ocorre a formação de CO que é usualmente identificado como o agente bloqueador da superfície eletródica devido à sua adsorção irreversível. Baseado em um estudo recente da reação de oxidação do metanol sobre Pt por espectroscopia de impedância eletroquímica (EIE), este trabalho teve por objetivo aplicar a técnica de EIE no estudo da eletrocatálise da reação de oxidação do metanol sobre fases intermetálicas ordenadas de PtMn, PtSb e PtSn em meio ácido, visto que os metais Mn, Sb e Sn por apresentarem característica oxifílica, podem formar mais facilmente espécies OH que promovem a oxidação de intermediários fortemente adsorvidos nos sítios ativos da superfície eletródica. Os intermetálicos também apresentam maior distância entre os sítios da platina o que pode favorecer uma configuração de adsorção vertical da molécula de CO que é mais fácil de oxidar quando comparado a uma configuração em ponte. Uma análise prévia da atividade catalítica desses materiais para a reação de oxidação do metanol foi realizada empregando-se as técnicas de voltametria cíclica cronoamperometria. Os resultados obtidos mostraram que o processo de oxidação do metanal utilizando os intermetálicos apresentou um deslocamento para valores menos positivos do potencial de início de oxidação...

‣ Electrochemical energy conversion in direct methanol fuel cells

Rangel, C. M.; Silva, R. A.; Verget, J.; Pinto, A.M.F.R.
Fonte: SPE08, XV Encontro da Sociedade Portuguesa de Electroquímica Publicador: SPE08, XV Encontro da Sociedade Portuguesa de Electroquímica
Tipo: Conferência ou Objeto de Conferência
Publicado em 03/09/2008 Português
Relevância na Pesquisa
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Direct methanol fuel cells (DMFCś) are promising candidates as portable power sources due to their lower weight, volume and high-energy density. They can potentially provide an energy content that exceeds current battery technology, with the possibility of instantaneous recharge. However, DMFCś have several serious drawbacks such as slow methanol oxidation kinetics, poisoning by CO of the catalyst surface, the high methanol crossover through the polymer membrane, the high costs of the Nafion membrane and catalyst. The flowing streams of fuel and oxidizer need to be evenly distributed over the entire surface of the catalyst layer in order to achieve a good performance together with an efficient removal of reaction products. This is achieved through the optimal design of the flow field. In this work the effect of flow field design on cell performance is studied, using polarization curves. A testing fuel cell was designed and implemented consisting of two stainless steel end plates, two sets of graphite collector plates, two carbon cloth diffusion layers, two catalyst layers of platinum black (0.70 mg.cm-2 and 0.75 mg.cm-2 Pt on cathode and anode, respectively) and an electrolyte polymer membrane (Nafion 117). Pt-Ru catalyst on the anode with a load of 4 mgcm-2 of catalyst was also studied. The active surface area of the cell is 25 cm2. An own built fuel cell and a Lyntech testing station were used in this work. The effects of temperature...

‣ Electrocatalytic oxidation of methanol: study with Pt:Mo dispersed catalysts

Oliveira Neto,Almir; Perez,Joelma; Napporn,Wilhelmin T.; 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 01/02/2000 Português
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The electrocatalytic oxidation of methanol on Pt:Mo dispersed on carbon prepared using an alternative method recently developed in this laboratory was investigated. The EDX analysis confirmed that the simultaneous reduction of the precursor salts of Pt and Mo leads to the presence of these materials at the nominal composition initially calculated. The addition of Mo to Pt causes an increase of the oxidation currents, but does not improve the catalytic effect for methanol oxidation. Tafel plots for various methanol concentrations showed the presence of two slopes. On line differential electrochemical mass spectrometry (DEMS) was used to investigate the distribution of products and intermediates in methanol oxidation.

‣ Methanol oxidation and assimilation in Hansenula polymorpha. An analysis by 13C n.m.r. in vivo.

Jones, J G; Bellion, E
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/12/1991 Português
Relevância na Pesquisa
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The metabolism of methanol was monitored in whole cells of the methylotrophic yeast Hansenula polymorpha by using [13C]methanol and n.m.r. in vivo. The main products observed under normal conditions were trehalose and glycerol, whereas cells that were starved before exposure to [13C]methanol also accumulated glutamate, glutamine and alanine; formate was also more prominent in spectra from starved cells. Cells exposed to high methanol concentration together with high oxygenation oxidized methanol extensively, leading to formaldehyde accumulation; label was not found in any subsequent metabolic products, indicating possible cell inactivation. [13C]Formate was incorporated into metabolic products in glucose-grown cells exposed to 150 mM-methanol for 3 h, but not in cells starved for 3 h, in which it was oxidized. At 21 degrees C such 3 h-starved cells showed a slower metabolism of [13C]methanol compared with those at 37 degrees C, and also converted methanol into formate rather than into assimilation products. The labelling pattern in trehalose from starved cells at 37 degrees C was consistent with methanol assimilation via the pentose phosphate pathway. Lack of appearance of labelled formaldehyde and formate during metabolism under normal conditions suggests that the linear oxidation pathway is not a major contributor to methanol oxidation; their appearance in extreme conditions suggests instead a more likely role in detoxification.

‣ Fisicoquímica de materiales para celdas de combustible PEM alimentadas con metanol; Physical-chemistry of materials for PEM fuel cells feeded with methanol

Franceschini, Esteban Andrés
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: info:eu-repo/semantics/doctoralThesis; tesis doctoral; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2012 Português
Relevância na Pesquisa
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Las celdas de combustible de membrana de intercambio protónico (PEM) alimentadas con metanol directo (DMPEM) utilizan en la actualidad como catalizadores catódico y anódico, platino y aleaciones platino/rutenio, respectivamente. Los catalizadores comerciales utilizados, están compuestos por nanopartículas de estos metales soportadas sobre partículas de carbón Vulcan XC72®. Estos catalizadores soportados presentan un bajo aprovechamiento del platino debido a que, para obtener una alta área electroquímicamente activa, se requiere la utilización de una gran cantidad de catalizador. La electrodeposición de platino y sus aleaciones con rutenio puede ser utilizada como método para obtener capas catalíticas de bajo espesor, mejorando el aprovechamiento del platino, mientras que la utilización de nanomoldes permite obtener una alta área electroquímicamente activa. En una primera etapa se consiguió sintetizar catalizadores mesoporosos utilizando como nanomolde un cristal líquido formado por un surfactante comercial, Brij 56® y un copolímero bloque comercial, Pluronic F127®. Estas síntesis mostraron ser reproducibles en diferentes soportes de electrodeposición. El diámetro de poro obtenido con la utilización del Brij 56® (entre 2...

‣ 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
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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.

‣ Highly active, carbon-supported, PdSn nano-core, partially covered with Pt, as catalysts for methanol oxidation

Wang,Hui; Linkov,Vladimir; Ji,Shan; Zhang,Wei; Lei,Ziqiang; Wang,Rongfang
Fonte: South African Journal of Chemistry Publicador: South African Journal of Chemistry
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2012 Português
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Carbon-supported, Pt partially covered, PdSn alloy nanoparticles (Pt-PdSn/C) were synthesized via a metathetical reaction of PdSn alloy nanoparticles, and a platinum precursor. The electrochemical activity was evaluated by methanol oxidation. The Pt-PdSn/C catalysts were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammograms (CV). TEM showed that Pt grows layer-by-layer on the surface of PdSn cores and the thickness of the Pt shell is 0.2 nm, about 1-2 monolayers thick. Cyclic voltammetry results showed that PdSn/C nanoparticles, partially covered by Pt, have a better electrocatalystic performance than conventional PtRu/C and PtPdSn/C catalysts. Electrochemical active surface areas of the Pt-PdSn/C was 2.30 times larger than that of PtRu/C and 1.8 times higher than that of PtPdSn/C catalysts. The results showed that a metathetical reaction is an efficient way of preparing, low Pt loading, highly active electrocatalyst, for methanol oxidation, thus offering great potential for producing Pt-based electrocatalyst for direct methanol fuel cells on a large scale.

‣ Beef-derived mesoporous carbon as highly efficient support for PtRulr electrocatalysts and their high activity for CO and methanol oxidation

Wang,Hui; Da,Huahua; Wang,Rongfang; Ji,Shan
Fonte: South African Journal of Chemistry Publicador: South African Journal of Chemistry
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2014 Português
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In this work, a low-cost and nitrogen-containing carbon with mesoporous pores and high surface area was synthesized by carbonizing a natural biomass precursor, i.e. beef. It is found that the prepared material has excellent textural properties such as high specific surface areas and large pore diameters. TEM images showed that the PtRuIr nanoparticles were well dispersed on the surface of carbonized beef (C-Beef). PtRuIr/C-Beef was highly active for methanol electro-oxidation. PtRuIr/C-Beef showed superior catalytic activity to PtRuIr/C, i.e. lower onset potential and higher oxidation current density. Cyclic voltammograms of CO electro-oxidation showed that PtRuIr/C-Beef catalyst was kinetically more active for CO electro-oxidation than PtRuIr deposited on conventional carbon support. The highly porous structure and low cost of carbonized beef can be widely used as support for highly dispersed metal nanoparticles to increase their electrochemical performance as electrocatalysts.

‣ Amorphous Pt@PdCu/CNT catalyst for methanol electrooxidation

Wang,Hui; Ji,Shan; Wang,Wei; Wang,Rongfang
Fonte: South African Journal of Chemistry Publicador: South African Journal of Chemistry
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2013 Português
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57.63132%
A multi-walled carbon nanotube-supported, Pt decorated nano-sized amorphous PdCu alloy cores (denoted as Pt@PdCu/CNT) catalyst with lower Pt loading is synthesized via a galvanic displacement reaction. The structure is examined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The electrochemical activity of the Pt@PdCu/CNT catalyst is tested by cyclic voltammogrametry (CV) and compared to that of PtRu/CNT catalysts. The results show that amorphous Pt@PdCu/CNT catalyst exhibits better electro-catalytic performances for methanol oxidation than its crystalline counterpart.