Methanol electrooxidation on well-characterized platinum-ruthenium bulk alloys

Gasteiger, Hubert A.; Marković, Nenad M.; Ross, Philip N.; Cairns, Elton J.

doi:10.1021/j100148a030

Cited by 960 publications

(897 citation statements)

References 9 publications

Supporting

Mentioning

796

Contrasting

Unclassified

Order By: Relevance

“…Taking into account that ensembles of Pt surface atoms are required for the adsorption of methanol on Pt [9] and that methanol does not adsorb on Sn or Ru [10], it follows that the promotor atoms should be present in low amounts, although this is not yet the general opinion. The optimal ratio M/Pt is still not definitely established, but it was confirmed by several authors [9,11,12] that a Pt-Ru electrode with a low Ru content (ca.…”

Section: Introductionmentioning

confidence: 99%

On the role of Ru and Sn as promotors of methanol electro-oxidation over Pt

1995

View full text Add to dashboard Cite

The role of Ru and Sn on the methanol oxidation over Pt was investigated for three different systems viz. Pt covered with adatom layers of Ru and Sn, electro-codeposited Pt-Ru and carbon supported Pt-Ru. By following the oxide growth on the Pt-promoter metal electrodes with ellipsometry it was found that in the presence of methanol the surface oxides of the promotor metal are no longer present on the surface. This supports the bifunctional model of the promotor action. DEMS measurements at Pt with submonolayer coverage of Ru or Sn revealed that the current efficiency of the methanol oxidation to CO 2 is increased in the presence of Ru or Sn and that the onset potential of the oxidation keeps lowering with increasing amounts of the promoting metal. On electrodeposited Pt-Ru systems the adsorption of methanol already takes place at potentials in the hydrogen range. These results seem to point to an electronic (ligand) effect. This is further corroborated by activity measurements at carbon supported Pt-Ru with very small particles, which show a tenfold higher activity compared with the Ru-free system.It is concluded that the promoting action of Ru and Sn may involve both a bifunctional and an electronic (ligand) effect.

show abstract

Section: Introductionmentioning

confidence: 99%

On the role of Ru and Sn as promotors of methanol electro-oxidation over Pt

1995

View full text Add to dashboard Cite

show abstract

“…Studies have been carried out mainly on platinum surfaces, both polycrystalline and single crystals, by means of different electrochemical approaches sometimes coupled to other in situ and on line techniques. [4][5][6][7][8][9][10][11][12][13][14][15][16] In most of these reports, the focus stands on the electrocatalytic aspects of the methanol oxidation and encompasses questions such as the relationship between reaction rate and applied potential, the impact of the interfacial structure on reaction rate and selectivity, and the nature and geometry of adsorbates, to list a few. By far less studied however are the issues related to the complex kinetic aspects associated to the electrooxidation of methanol.…”

mentioning

confidence: 99%

Oscillatory instabilities during the electrocatalytic oxidation of methanol on platinum

Martins¹,

Batista²,

Sitta³

et al. 2008

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

Descreve-se neste artigo a observação experimental de dinâmica oscilatória durante a oxidação eletrocatalítica de metanol sobre platina. Além das, previamente relatadas, oscilações de potencial, oscilações de corrente obtidas sob controle potenciostático também são apresentadas. A região de existência de oscilações de corrente é mapeada no plano de bifurcação voltagem aplicada x resistência. Conjuntamente com investigações eletroquímicas, espectroscopia FTIR in situ também foi aplicada nestes estudos. Apesar de não ter sido possível acompanhar eventuais variações de intermediários reacionais durante as oscilações, tais experimentos revelaram que a cobertura média de monóxido de carbono permanece consideravelmente alta durante as oscilações. Os resultados são discutidos e comparados com as oscilações observadas na eletrooxidação de ácido fórmico, um sistema cujo comportamento é mais entendido e amplamente fundamentado por dados espectroscópicos obtidos in situ.It is described in this paper the experimental observation of oscillatory dynamics during the electrocatalytic oxidation of methanol on platinum. Besides the previously reported potential oscillations, current oscillations obtained under potentiostatic control are also presented. The existence region of current oscillations is mapped in an applied voltage x resistance bifurcation diagram. Conjointly with electrochemical investigations, in situ FTIR spectroscopy was also employed in the present studies. Although we were not able to follow eventual intermediate coverage changes during the oscillations, those experiments revealled that the mean coverage of adsorbed carbon monoxide remains appreciably high along the oscillations. Results are discussed and compared with the oscillations observed in the electrooxidation of formic acid, a system whose behavior is more understood and widely supported by in situ spectroscopic data. Keywords: current and potential oscillations, methanol, electrocatalysis, in situ FTIR IntroductionMethanol has been pointed as one of the most promising organic molecules to be used in large scale energy conversion systems, as in the so-called direct methanol fuel cells (DMFC). [1][2][3] Limitations associated to the high overpotential and the existence of parallel reaction pathways makes its understanding a rather challenging task. Studies have been carried out mainly on platinum surfaces, both polycrystalline and single crystals, by means of different electrochemical approaches sometimes coupled to other in situ and on line techniques. [4][5][6][7][8][9][10][11][12][13][14][15][16] In most of these reports, the focus stands on the electrocatalytic aspects of the methanol oxidation and encompasses questions such as the relationship between reaction rate and applied potential, the impact of the interfacial structure on reaction rate and selectivity, and the nature and geometry of adsorbates, to list a few. By far less studied however are the issues related to the complex kinetic aspects associated to the electrooxidation of methanol.In o...

show abstract

“…A surface charge density of 210 mC cm -2 was assumed. 23 The logarithm of the anodic peak current (between 0.75 and 0.85 V) (associated with the methanol electrooxidation) was plotted as a function of the logarithm of methanol concentration (inset of Figure 6a Nafion ® and chitosan/PVS/Nafion ® membranes toward compartment B, which is higher for cell-1 as compared to cell-2.…”

Section: Resultsmentioning

confidence: 99%

“…A surface charge density of 210 mC cm -2 was assumed. 23 The logarithm of the anodic peak current (between 0.75 and 0.85 V) (associated with the methanol electrooxidation) was plotted as a function of the logarithm of methanol concentration (inset of Figure 6a), which was used as a calibration curve. Figures 6b and 6c depict the plots of cyclic voltammetry between 0.5 and 1.1 V during the positive scan for the Pt electrode in compartment B of cell-1 and cell-2, respectively, as a function of time after methanol addition in compartment A.…”

mentioning

confidence: 99%

Self-assembled films from chitosan and poly(vinyl sulfonic acid) on Nafion® for direct methanol fuel cell

Vinhola¹,

Facci²,

Dias³

et al. 2012

J. Braz. Chem. Soc.

View full text Add to dashboard Cite

Filmes de quitosana/poli(ácido vinilsulfônico) (PVS) foram depositados sobre membranas de Nafion ® a partir do método camada por camada (LbL), visando o seu uso em células a combustível de metanol direto (DMFC). Métodos computacionais e espectros de infravermelho com transformada de Fourier (FTIR) sugerem a formação de um par iônico entre o grupo sulfônico do PVS e o grupo amino protonado da quitosana, o qual promove o crescimento dos filmes LbL sobre a membrana de Nafion ® , assim como impede parcialmente a passagem de metanol. Experimentos de cronopotenciometria e varredura linear de potencial foram realizados a fim de se investigar a passagem de metanol através das membranas de Nafion ® e quitosana/PVS/Nafion ® em uma célula a diafragma. Os valores de resistência iônica associada ao transporte de prótons nas membranas de Nafion ® e quitosana/PVS/Nafion ® são próximos, de acordo com as medidas de impedância elétrica devido à pequena espessura do filme LbL. Assim, espera-se um melhor desempenho da DMFC, uma vez que a resistência do filme automontado é insignificante comparada ao resultado associado à passagem de metanol através das membranas.Chitosan/poly(vinyl sulfonic acid) (PVS) films have been prepared on Nafion ® membranes by the layer-by-layer (LbL) method for use in direct methanol fuel cell (DMFC). Computational methods and Fourier transform infrared (FTIR) spectra suggest that an ionic pair is formed between the sulfonic group of PVS and the protonated amine group of chitosan, thereby promoting the growth of LbL films on the Nafion ® membrane as well as partial blocking of methanol. Chronopotentiometry and potential linear scanning experiments have been carried out for investigation of methanol crossover through the Nafion ® and chitosan/PVS/Nafion ® membranes in a diaphragm diffusion cell. On the basis of electrical impedance measurements, the values of proton resistance of the Nafion ® and chitosan/PVS/Nafion ® membranes are close due to the small thickness of the LbL film. Thus, it is expected an improved DMFC performance once the additional resistance of the self-assembled film is negligible compared to the result associated with the decrease in the crossover effect.Keywords: chitosan, direct methanol fuel cell, proton exchange membrane, crossover effect, methanol permeability IntroductionDirect methanol fuel cells (DMFCs) are the most promising portable, stationary power sources with application in several fields. In these cells, methanol and air are continually injected into the anode and cathode compartments, respectively, thus providing energy with high efficiency. Methanol has been largely employed as fuel once it is abundant and inexpensive. Even though DMFCs produce carbon dioxide, which is released into the atmosphere, their high efficiency guarantees low pollution as compared to other power sources. [1][2][3] One drawback of DMFCs is the so-called crossover effect, through which methanol leaves the anodic compartment and crosses the proton exchange membrane (PEM), thereby promoting cell de...

show abstract

Methanol electrooxidation on well-characterized platinum-ruthenium bulk alloys

Cited by 960 publications

References 9 publications

On the role of Ru and Sn as promotors of methanol electro-oxidation over Pt

On the role of Ru and Sn as promotors of methanol electro-oxidation over Pt

Oscillatory instabilities during the electrocatalytic oxidation of methanol on platinum

Self-assembled films from chitosan and poly(vinyl sulfonic acid) on Nafion® for direct methanol fuel cell

Contact Info

Product

Resources

About