Decreases in the inhibition of the electrocatalyzed oxidation of formic acid by carbon monoxide

Schell, Mark; Albahadily, F. N.; Safar, James

doi:10.1016/0022-0728(93)80307-4

Cited by 20 publications

(13 citation statements)

References 16 publications

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“…In a certain range of frequency used, either the oxidation current is increased or the overpotential is decreased, implying an advantage of forced oscillatory operation over stable steady-state operation. 15,16 The gain in both reaction rate and efficiency has been demonstrated in biological reactions as well, where the biochemical reaction system exhibits autonomous oscillations. 7,9 A perturbation to one of the reactants ͑i.e., oxygen influx͒ in the form of a sinusoidal wave was used instead of steady flux.…”

Section: Discussionmentioning

confidence: 98%

Higher Power Output in a PEMFC Operating under Autonomous Oscillatory Conditions in the Presence of CO

Zhang

Datta

2004

Electrochem. Solid-State Lett.

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Time-averaged cell voltage, cell efficiency, and power density in an autonomous oscillatory state was higher than that in stable steady-state for a proton exchange membrane fuel cell ͑PEMFC͒ operating in the presence of CO in the anode feed reformate gas. The average power density under such an oscillatory state at 55°C is twice that under a stable steady state. The average cell voltage and power density gain are due to the decrease of the time-averaged anode overpotential in the oscillatory state. This report thus provides experimental evidence that autonomous oscillatory operation of fuel cells in the presence of CO can increase the power output as compared to that in stable steady-state operation.Periodic or chaotic behavior has been observed in both homogeneous and heterogeneous reaction processes, and especially in electrochemical systems. 1 If such systems are well-mixed, only temporal periodic variations of the variables appear. Otherwise, spatiotemporal patterns may be observed, e.g., in the concentration of adsorbed species on an electrode surface. 2 The literature is replete with reports of oscillatory phenomena in electrochemical systems, and the mechanistic understanding of the origin of such oscillations is being continually advanced. 3-6 Generally, the periodic behavior of an electrochemical system is due to the interplay of nonlinear electrode kinetics, mass transport, and the external electrical circuitry. The mathematical models for these phenomena contain nonlinear differential equations for reactant concentrations, coverage of surface species, and current or voltage as variables.Oscillations in reaction systems were considered puzzling and largely irrelevant. Later, there was an effort to search for ways to exploit nonlinear kinetics. 7,8 For instance, the reaction rate is increased in a forced oscillatory biochemical reaction. 9 Similar phenomena were also observed in conventional chemical reactions with nonlinear kinetics. 10 In these examples it was demonstrated that efficiency could be improved by operating in a forced oscillatory state. With the improved theoretical understanding of periodic behavior in electrochemical systems, the expectations of their practical utility are also increasing. 7,8 Recently, we found that sustained potential oscillations exist in proton exchange membrane fuel cells ͑PEMFCs͒ fed with H 2 containing low levels of CO when operated under constant current conditions. 11 The oscillations were determined to be due to the nonlinear kinetics of the anode reactions coupled with the mass and charge conservation. Here we present our findings on increased power output of PEMFCs when operated under such oscillatory conditions. ExperimentalThe experimental details can be found in our previous work. 11 In short, two pieces of electrode were bonded to either side of a solid polymer electrolyte membrane ͑Nafion 115͒. An electrode containing 0.35 mg/cm 2 PtRu ͑atomic ratio 1:1, E-TEK͒ was used at the anode, exposed to a simulated reformate gas (H 2 containing low levels of CO, ...

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Section: Discussionmentioning

confidence: 98%

Higher Power Output in a PEMFC Operating under Autonomous Oscillatory Conditions in the Presence of CO

Zhang

Datta

2004

Electrochem. Solid-State Lett.

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“…28,29 The biochemical system efficiency can also be enhanced within the autonomous oscillations themselves. 30 The enhanced output power density in the oscillatory cell is consistent with the oscillations appearing due to the self-sustained efforts by the whole system to maximize efficiency.…”

Section: Output Power Density Oscillationsmentioning

confidence: 99%

Spontaneous oscillations of cell voltage, power density, and anode exit CO concentration in a PEM fuel cell

Lü¹,

Rihko‐Struckmann²,

Sundmacher³

2011

Phys. Chem. Chem. Phys.

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The spontaneous oscillations of the cell voltage and output power density of a PEMFC (with PtRu/C anode) using CO-containing H 2 streams as anodic fuels have been observed during galvanostatic operating. It is ascribed to the dynamic coupling of the CO adsorption (poisoning) and the electrochemical CO oxidation (reactivating) processes in the anode chamber of the single PEMFC. Accompanying the cell voltage and power density oscillations, the discrete CO concentration oscillations at the anode outlet of the PEMFC were also detected, which directly confirms the electrochemical CO oxidation taking place in the anode chamber during galvanostatic operating.

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“…Our focus here is on the nature of the oscillations rather than a detailed mechanistic analysis. In this respect it is interesting to note that Schell et al [20] found that in the periodically driven system more formic acid follows the "direct" pathway than in the unperturbed system even though the average current applied was the same. Therefore improved understanding of the oscillations may lead to direct beneficial effects for the efficiency of formic acid anodes.…”

Section: Introductionmentioning

confidence: 97%

Impedance study of formic acid oxidation on platinum electrodes

Seland

Tunold

Harrington

2008

Electrochimica Acta

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Decreases in the inhibition of the electrocatalyzed oxidation of formic acid by carbon monoxide

Cited by 20 publications

References 16 publications

Higher Power Output in a PEMFC Operating under Autonomous Oscillatory Conditions in the Presence of CO

Higher Power Output in a PEMFC Operating under Autonomous Oscillatory Conditions in the Presence of CO

Spontaneous oscillations of cell voltage, power density, and anode exit CO concentration in a PEM fuel cell

Impedance study of formic acid oxidation on platinum electrodes

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