Formate, an Active Intermediate for Direct Oxidation of Methanol on Pt Electrode

Chen, Yan‐Xia; Miki, Atsushi; Ye, Shen; Sakai, Hidetada; Osawa, Masatoshi

doi:10.1021/ja029044t

Cited by 479 publications

(460 citation statements)

References 12 publications

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“…Formaldehyde is then nearly completely hydrated to methylene glycol, which will be oxidized to formic acid in solution, either directly (reaction 12) or through adsorbed formate (reaction 11 and 13). Finally, this scheme also explain the fact that formate was observed on platinum surfaces during the electrochemical oxidation of methanol (reactions 8-12), formic acid (reaction 13) and formaldehyde (reactions 10-13), as well as the fact that CO ads was found during the oxidation of formaldehyde and of formic acid (reactions 10, 11, and 16) by various authors [44,[49][50][51], substantiating the proposed reaction scheme.…”

Section: Methanol Electrooxidation On Ptsupporting

confidence: 53%

Mechanisms of Carbon Monoxide and Methanol Oxidation at Single-crystal Electrodes

et al. 2007

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The electrochemical oxidation of carbon monoxide and methanol on single-crystal noble metal electrodes has been studied using cyclic voltammetry, chronoamperometry, in situ FTIR spectroscopy, online electrochemical mass spectrometry, and theoretical methods. The oxidation of CO was found to be enhanced by steps and defects. Furthermore, the surface diffusion rate was found to have a significant influence on the kinetics of the oxidation process: for high diffusion rates, such as the oxidation of CO on platinum, the kinetics can be described by a mean field model, while for low diffusion rates, such as CO oxidation on rhodium in sulfuric acid, a nucleationand-growth model was found to be more suitable. Voltammetric and mass spectrometric measurements on the oxidation of methanol on platinum indicate that steps enhance the overall reaction rate. In general, the selectivity towards the direct oxidation pathway through soluble intermediates was found to be higher in the absence of strongly adsorbing anions. In both perchloric and sulfuric acid, this selectivity was also found to increase with increasing step density. In sulfuric acid, Pt(111) shows the highest relative contribution for the direct pathway of all surfaces studied in that electrolyte. Based on these results, a detailed reaction scheme for the electrochemical oxidation of methanol is presented.

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Section: Methanol Electrooxidation On Ptsupporting

confidence: 53%

Mechanisms of Carbon Monoxide and Methanol Oxidation at Single-crystal Electrodes

et al. 2007

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“…10,14 Moreover, formate has also been observed as an intermediate during methanol electrooxidation on platinum. 53 Both the formation and further electrooxidation of those intermediates certainly take part as a current carrier, contributing to the active (non-CO ad ) pathway. Under oscillatory conditions, however, this contribution would occur only in the CO free small portion of the surface.…”

Section: Resultsmentioning

confidence: 99%

Oscillatory instabilities during the electrocatalytic oxidation of methanol on platinum

Martins¹,

Batista²,

Sitta³

et al. 2008

J. Braz. Chem. Soc.

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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...

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“…29,[45][46][47] However, due to the strong binding of CO* on the surface, which blocks the active sites for this reaction, this mechanism will likely produce only low currents. Thus, we restrict our analysis to electro-oxidation pathways that go through CO* (the indirect mechanism).…”

Section: Resultsmentioning

confidence: 99%

Bifunctional anode catalysts for direct methanol fuel cells

Rossmeisl

Ferrin

Tritsaris

et al. 2012

Energy Environ. Sci.

164

126

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Using the binding energy of OH* and CO* on close-packed surfaces as reactivity descriptors, we screen bulk and surface alloy catalysts for methanol electro-oxidation activity. Using these two descriptors, we illustrate that a good methanol electro-oxidation catalyst must have three key properties: (1) the ability to activate methanol, (2) the ability to activate water, and (3) the ability to react off surface intermediates (such as CO* and OH*). Based on this analysis, an alloy catalyst made up of Cu and Pt should have a synergistic effect facilitating the activity towards methanol electro-oxidation. Using these two reactivity descriptors, a surface PtCu 3 alloy is proposed to have the best catalytic properties of the Pt-Cu model catalysts tested, similar to those of a Pt-Ru bulk alloy. To validate the model, experiments on a Pt(111) surface modified with different amounts of Cu adatoms are performed. Adding Cu to a Pt(111) surface increases the methanol oxidation current by more than a factor of three, supporting our theoretical predictions for improved electrocatalysts.

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Formate, an Active Intermediate for Direct Oxidation of Methanol on Pt Electrode

Cited by 479 publications

References 12 publications

Mechanisms of Carbon Monoxide and Methanol Oxidation at Single-crystal Electrodes

Mechanisms of Carbon Monoxide and Methanol Oxidation at Single-crystal Electrodes

Oscillatory instabilities during the electrocatalytic oxidation of methanol on platinum

Bifunctional anode catalysts for direct methanol fuel cells

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