Observation of several different temporal patterns in the oxidation of formic acid at a rotating platinum-disk electrode in an acidic medium

Albahadily, F. N.; Schell, Mark

doi:10.1016/0022-0728(91)85064-v

Cited by 92 publications

(89 citation statements)

References 32 publications

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“…In contrast to previous statements, [55][56][57][58] Behm and co-workers [59][60][61] found that an adsorbed bridge-bonded formate species does not take part as a reaction intermediate in the direct pathway, but rather it acts as a spectator that blocks the catalyst surface in the, dominant, direct pathway. The authors propose a triple pathway mechanism which includes the direct pathway, 61 HCOOH Oscillatory kinetics during the electrooxidation of formic acid on platinum has been observed many times [62][63][64][65][66][67][68][69][70][71] and is known to result from the presence of a negative differential resistance in an N-shaped current potential curve. 72 The phenomenon has been explained in terms of the interaction between positive and negative feedback loops acting on the electrode potential and can be rationalized in terms of the interaction of 73 (a) surface poisoning along the indirect pathway, (b) cleaning of the surface by the reaction between adsorbed carbon monoxide and oxygenated species, and (c) feedback between the total surface coverage and the electrode potential.…”

Section: Resultsmentioning

confidence: 99%

Temperature (Over)Compensation in an Oscillatory Surface Reaction

et al. 2008

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Biological rhythms are regulated by homeostatic mechanisms that assure that physiological clocks function reliably independent of temperature changes in the environment. Temperature compensation, the independence of the oscillatory period on temperature, is known to play a central role in many biological rhythms, but it is rather rare in chemical oscillators. We study the influence of temperature on the oscillatory dynamics during the catalytic oxidation of formic acid on a polycrystalline platinum electrode. The experiments are performed at five temperatures from 5 to 25°C, and the oscillations are studied under galvanostatic control. Under oscillatory conditions, only non-Arrhenius behavior is observed. Overcompensation with temperature coefficient (q 10 , defined as the ratio between the rate constants at temperature T + 10°C and at T) < 1 is found in most cases, except that temperature compensation with q 10 ≈ 1 predominates at high applied currents. The behavior of the period and the amplitude result from a complex interplay between temperature and applied current or, equivalently, the distance from thermodynamic equilibrium. High, positive apparent activation energies were obtained under voltammetric, nonoscillatory conditions, which implies that the non-Arrhenius behavior observed under oscillatory conditions results from the interplay among reaction steps rather than from a weak temperature dependence of the individual steps.

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Section: Resultsmentioning

confidence: 99%

Temperature (Over)Compensation in an Oscillatory Surface Reaction

et al. 2008

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“…Those features are rather astonishing if one considers the plethora of oscillatory patterns observed for instance in the electrooxidation of formic acid. [28][29][30][31][32][33][34] In the present work we report the investigation of the oscillatory instabilities in the methanol electrooxidation reaction on a polycrystalline platinum electrode and in aqueous sulfuric acid media. Besides conventional electrochemical experiments under potentiostatic and galvanostatic control, in situ FTIR spectroscopy was also employed to quantify the mean carbon monoxide coverage during the oscillations.…”

Section: Introductionmentioning

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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“…Although the regeneration oscillation may be one of mixed-mode oscillations, 18,19 it has a distinctive feature that the metastable high potential is higher than 1.0 V, which potential value is a sign of the cease of ordinary oscillations, and the duration of the metastable state is long, sometimes longer than 1 h, as shown later. The regeneration oscillation is similar to the "drastically" changed oscillation observed by Chen et al 31,32 with 5.0 © 10 ¹6 M chloride ions and 0.10 M HCOONa in a 0.50 M perchloric acid solution at room temperature, although the duration of the high potential state is very short.…”

Section: Resultsmentioning

confidence: 72%

“…It is also established [14][15][16][17] that the indirect path involves adsorbed CO in common for oxidations of the three C 1 -compounds. It is well known 8,[18][19][20][21][22] that adsorbed CO plays a crucial role in the oscillation. Gojuki et al 9 have recently proposed that adsorbed water is also involved in the oscillation.…”

Section: Introductionmentioning

confidence: 99%

Regeneration Oscillation Observed during Oxidation of Methanol, Formic Acid, and Formaldehyde with Chloride Ions

et al. 2014

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A new type of oscillation, which we name regeneration oscillation, is investigated in detail. The regeneration oscillation is the ordinary potential oscillation with the higher turning potential lower than 0.85 V appearing repeatedly after the potential stays at a value higher than 1.0 V for a long time, of the order of 10 min or an hour. The oscillation has been observed during the oxidation of methanol, formaldehyde, and formic acid at 315 K when their concentrations are high, 1 or 10 mol/L (M), in the presence of high chloride ion concentrations, such as 10 −2 M, at a current far lower than the maximum current for the appearance of ordinary oscillation. The reason for the appearance of regeneration oscillation has been found by voltammetry and surface-enhanced infrared absorption spectroscopy to be due to the presence of two potentials for oxidizing adsorbed CO, one shifting to a value higher than 1.0 V and the other remaining unchanged, with increasing chloride ion concentration.

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Observation of several different temporal patterns in the oxidation of formic acid at a rotating platinum-disk electrode in an acidic medium

Cited by 92 publications

References 32 publications

Temperature (Over)Compensation in an Oscillatory Surface Reaction

Temperature (Over)Compensation in an Oscillatory Surface Reaction

Oscillatory instabilities during the electrocatalytic oxidation of methanol on platinum

Regeneration Oscillation Observed during Oxidation of Methanol, Formic Acid, and Formaldehyde with Chloride Ions

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