Trapping Electrochemical Oscillations between Self‐Organized Potential Walls

Varela, Hamilton; Bonnefont, Antoine; Krischer, Katharina

doi:10.1002/cphc.200300922

Cited by 7 publications

(4 citation statements)

References 32 publications

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“…For example, electrochemical devices are conceivable where local activation of a poisoned electrocatalytic surface is sufficient to restore complete activity, if the interface can support the propagation of active fronts; the three-electrodes setup with the counter electrode sufficiently far away from the working electrode could be used in previous studies. 53,93,[97][98][99] However, there is no reference electrode in real fuel cells, and working and counter electrodes are often very close together in order to minimise ohmic losses in the electrolyte. In such cases, the coupling relevant for one electrode will not only depend on the potential distribution along itself, but also on the distribution at the other electrode.…”

Section: Nonlinear Electro-oxidation and Its Possible Application In ...mentioning

confidence: 99%

Understanding underlying processes in formic acid fuel cells

Uhm

Lee

2009

Phys. Chem. Chem. Phys.

172

129

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Obsolescence, defined as the process of declining performance of buildings, is a serious threat for the value, the usefulness and the life span of built properties. Thomsen and van der Flier (2011) developed a model in which obsolescence is categorised on the basis of two distinctions, i.e. between endogenous and exogenous cause-effect relationships and between physical and behavioural cause-effect relationships. In this way, the model presents a classification of underlying factors of obsolescence. However, these underlying factors, more specifically the underlying cause-effect relations, are still a black box. In this paper, the box is further disclosed by tracking back the underlying processes, resulting in a series of prototypes of detailed hypothetic cause-effect mechanisms. Applied to the adapted model, the results are initially tested on an iconic chocolate factory. Conclusions are drawn about the results and more generally about the usability and the further development of the model.

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Section: Nonlinear Electro-oxidation and Its Possible Application In ...mentioning

confidence: 99%

Understanding underlying processes in formic acid fuel cells

Uhm

Lee

2009

Phys. Chem. Chem. Phys.

172

129

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“…The situation is, however, more complicated in the second case, and the electro-oxidation of bulk CO alone might undergo kinetic instabilities of different types. [23][24][25][26][27] The electrocatalytic oxidation of hydrogen in hydrogen/carbon monoxide mixtures is of utmost importance for low temperature fuel cells, because hydrogen obtained from the reform of other fuels contains at least traces of CO, which considerably lowers the overall efficiency of the fuel cell. Besides the cited data of half-cell experiments, there are also several recent papers on the kinetic instabilities in low temperature proton exchange membrane fuel cells ͑PEMFCs͒ fed with H 2 /CO mixtures.…”

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confidence: 99%

Complex Oscillatory Response of a PEM Fuel Cell Fed with H[sub 2]/CO and Oxygen

Mota-Lima

Lopes

Ticianelli

et al. 2010

J. Electrochem. Soc.

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Oscillatory kinetics is commonly observed in the electrocatalytic oxidation of most species that can be used in fuel cell devices. Examples include formic acid, methanol, ethanol, ethylene glycol, and hydrogen/carbon monoxide mixtures, and most papers refer to half-cell experiments. We report in this paper the experimental investigation of the oscillatory dynamics in a proton exchange membrane ͑PEM͒ fuel cell at 30°C. The system consists of a Pt/C cathode fed with oxygen and a PtRu ͑1:1͒/C anode fed with H 2 mixed with 100 ppm of CO, and was studied at different cell currents and anode flow rates. Many different states including periodic and nonperiodic series were observed as a function of the cell current and the H 2 /CO flow rate. In general, aperiodic/ chaotic states were favored at high currents and low flow rates. The dynamics was further characterized in terms of the relationship between the oscillation amplitude and the subsequent time required for the anode to get poisoned by carbon monoxide. Results are discussed in terms of the mechanistic aspects of the carbon monoxide adsorption and oxidation.

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“…The formation of Pt-(hydr)oxides introduces further reaction steps that also interfere with the oscillatory behavior thereby changing the homogeneous dynamics drastically. 28,29 For this reason these states were not considered in the present investigation. The electrolyte composition was the same in all experiments and chosen such that, in the absence of global coupling, the system exhibited a transition from a spatially modulated limit cycle to electrochemical turbulence upon increase of U.…”

Section: Resultsmentioning

confidence: 99%

A hierarchy of global coupling induced cluster patterns during the oscillatory H2-electrooxidation reaction on a Pt ring-electrode

Varela

Beta

Bonnefont

et al. 2005

Phys. Chem. Chem. Phys.

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We report experimental results on spatiotemporal pattern formation during the oscillatory hydrogen electrooxidation reaction on a Pt ring-electrode under negative (desynchronizing) global coupling (GC). Spatially one-dimensional profiles of the interfacial potential drop along the angular direction of the ring electrode are recorded by means of a potential probe. The dynamics is investigated as a function of two control parameters, the applied voltage U and the strength of the global coupling. The latter is adjusted either by varying the distance between the working electrode (WE) and the reference electrode (RE) or by inserting a negative impedance device in series with the WE. In the absence of global coupling, uniform oscillations were destabilized by migration coupling, and electrochemical turbulence developed at large values of U (H. Varela, C. Beta, A. Bonnefont and K. Krischer, Phys. Rev. Lett., 2005, 94, 174104; ). Already low global coupling strengths sufficed to suppress turbulence. Instead, regular two-phase clusters formed. At higher coupling strength, a second type of two-phase cluster was observed as well as two types of irregular cluster patterns, which were connected with an irregular motion of the cluster boundaries and the emergence and disappearance of clusters through splitting and merging of the boundaries, respectively. Upon increasing the coupling strength even further, five-phase clusters were stabilized and at the highest coupling strength applied the cluster patterns transformed into strongly modulated pulses. The two types of two-phase clusters and the five-phase clusters are analyzed employing several signal processing techniques.

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Trapping Electrochemical Oscillations between Self‐Organized Potential Walls

Cited by 7 publications

References 32 publications

Understanding underlying processes in formic acid fuel cells

Understanding underlying processes in formic acid fuel cells

Complex Oscillatory Response of a PEM Fuel Cell Fed with H[sub 2]/CO and Oxygen

A hierarchy of global coupling induced cluster patterns during the oscillatory H2-electrooxidation reaction on a Pt ring-electrode

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