Superstable nonequilibrium states

Amini, Afshin; Xu, Yan; Schell, Mark

doi:10.1063/1.468632

Cited by 5 publications

(3 citation statements)

References 10 publications

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“…The nonuniversal behavior we first discuss involves transients that occur close to a period-doubling bifurcation. Preceding any period-doubling bifurcation, the approach to the limit cycle in phase space changes from a monotone to an alternating one (universal behavior). − Figure displays current−density vs potential curves ( i / E curves) that represent alternating approaches to the limiting state; part a is for methanol, part b is for ethylene glycol, and part c is for glycerol. During each cycle, the i / E curve is on the side of the limiting cycle that is opposite to the side it was on during the previous cycle.…”

Section: Universal and Nonuniversal Transient Behaviormentioning

confidence: 99%

Mechanism for the Electrocatalyzed Oxidation of Glycerol Deduced from an Analysis of Chemical Instabilities

Schell

Zdraveski

1996

J. Phys. Chem.

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The electrocatalyzed oxidation of glycerol in alkaline solution is compared with the oxidations of ethylene glycol and methanol. An analysis of behaviors caused by instabilities provides strong evidence that the elementary reactions that dominate the oxidation of glycerol are the same as those that dominate the oxidation of methanol. These reactions include the formation of surface bonded CO and its reaction with surface bonded hydroxyl radicals. The reactions that precede the dominant reactions in the oxidation of glycerol are relatively fast and must involve cleavage of C−C bonds. Evidence from phase diagrams indicates that the most probable sequence for the fast reactions requires a sufficient number of neighboring vacant sites to produce three surface-bonded CO complexes for each glycerol molecule. Reaction sequences that lead to zero, one, or two CO complexes occur with small probability.

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Section: Universal and Nonuniversal Transient Behaviormentioning

confidence: 99%

Mechanism for the Electrocatalyzed Oxidation of Glycerol Deduced from an Analysis of Chemical Instabilities

Schell

Zdraveski

1996

J. Phys. Chem.

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“…[2][3][4][5][6][7][8][9][10][11] Varela and Krischer 12,13 also found HOV during electrooxidation of hydrogen in acid media. In any case, two conditions are necessary to observe HOV: the reaction should contain an inhibition region at high overpotential, in general connected with oxide formation, giving origin to a peak current; an expressive ohmic drop, given by the product of current (I) and resistance (R), provided by low concentration supporting electrolyte or an external resistance.…”

Section: Introductionmentioning

confidence: 99%

“…17,18 When applied to electrocatalysis, gold also tends to be a selective catalyst due to its weak adsorption properties. 19 Taking the ethanol electrooxidation reaction (EER) into account, gold is a poor catalyst in pH lower than 8,20 depicting slight activity in potentials higher than 1.00 V only in non-adsorbing anion solution (e.g., HClO 4 ). In the presence of phosphate ions the ethanol oxidation currents are difficult to discern from those obtained in absence of ethanol.…”

Section: Introductionmentioning

confidence: 99%

High Order Cyclic Voltammograms During Electrooxidation of Ethanol Catalyzed by Gold

Silva¹,

Maruyama²,

Sitta³

2017

J. Braz. Chem. Soc.

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Under fixed limits, potential sweeps in some electrochemical systems depict current profile whose shape repeats in every n cycle (with n > 1), receiving the name of high order voltammograms (HOV). HOV have been observed during electrooxidation of organic molecules catalyzed mainly by Pt. The present study shows HOV behavior during ethanol electrooxidation reaction onto gold in alkaline media. Firstly, a strong dependence of HOV with minimum potential is remarkable in this system and has not been considered in previous numeric models. Moreover, due to high sensibility of HOV to surface conditions, it was possible to follow effects caused by cation interactions with adsorbed oxygenated species. Keywords: high order voltammograms, ethanol electrooxidation, gold catalyst, cation effects IntroductionIn a conventional cyclic voltammetry experiment the applied potential is continuously changed at a fixed rate between two limits (E min and E up ) while the current is registered. 1 The characteristic current-potential plot is called cyclic voltammogram and the current value at a given potential and scan direction can depict three behaviors: it becomes unchanged along the cycles; increase or decrease monotonically along the cycles; repeat its profile every set of cycles, that can be periodic, i.e., observed in every n cycle (n > 1) or aperiodic, in which n admits more than one value along the experiment. These voltammograms, periodic or aperiodic, are called high order voltammograms (HOV) and in contrast to the other cases, they are much less explored in the electrochemical field.Examples of HOV can be found for several small organic molecules electrooxidation reactions catalyzed by Pt in both alkaline and acid media. [2][3][4][5][6][7][8][9][10][11] Varela and Krischer 12,13 also found HOV during electrooxidation of hydrogen in acid media. In any case, two conditions are necessary to observe HOV: the reaction should contain an inhibition region at high overpotential, in general connected with oxide formation, giving origin to a peak current; an expressive ohmic drop, given by the product of current (I) and resistance (R), provided by low concentration supporting electrolyte or an external resistance.Ohmic drop allows the separation of applied potential (E) and the potential at interphase (ϕ) once E = ϕ + IR.14 When E up is set slightly more negative than the potential of peak current, the first cycles have almost the same current during positive and negative going scans, (small hysteresis) being classified as S cycles, but along the cycles, the current decreases and ϕ becomes higher and higher until reaching the region of current inhibition. At this point, ϕ quickly increases and oxides cover the surface. This condition makes the current in the negative going scan very distinct from that in the positive, i.e., with a large hysteresis and the cycle being classified as L. If the cycle after the L is the S, the initial condition is restored and the HOV is observed. 15 Indeed, to observe HOV the system should contain some pa...

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Mechanistic explanation for a subharmonic bifurcation and variations in behaviour in the voltammetric oxidations of ethanol, 1-propanol and 1-butanol

Amini

Schell

1995

Journal of Electroanalytical Chemistry

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Superstable nonequilibrium states

Cited by 5 publications

References 10 publications

Mechanism for the Electrocatalyzed Oxidation of Glycerol Deduced from an Analysis of Chemical Instabilities

Mechanism for the Electrocatalyzed Oxidation of Glycerol Deduced from an Analysis of Chemical Instabilities

High Order Cyclic Voltammograms During Electrooxidation of Ethanol Catalyzed by Gold

Mechanistic explanation for a subharmonic bifurcation and variations in behaviour in the voltammetric oxidations of ethanol, 1-propanol and 1-butanol

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