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Fehribach, Joseph D.; Prins-Jansen, J.A.; Hemmes, K.; Wit, J.H.W. de; Call, Frederick W.

doi:10.1023/a:1004003022974

Cited by 16 publications

(10 citation statements)

References 2 publications

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“…In addition, for low oxygen partial pressures, the influence of mass transfer limitations appears to be large even at low current densities, which makes kinetic studies very difficult. In a newer model, called Electrochemical-Potential Model [22], the electrochemical potentials for individual species are combined to define component potentials which are separated by the slow chemical and/or electrochemical reactions. Then, the reaction rates for the slow reactions are assumed to be proportional to the differences in these component potentials.…”

Section: Nomenclaturementioning

confidence: 99%

Three-dimensional modeling of polarization characteristics in molten carbonate fuel cells using peroxide and superoxide mechanisms

Ramandi

Berg

Dinçer

2012

Journal of Power Sources

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Section: Nomenclaturementioning

confidence: 99%

Three-dimensional modeling of polarization characteristics in molten carbonate fuel cells using peroxide and superoxide mechanisms

Ramandi

Berg

Dinçer

2012

Journal of Power Sources

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“…Let ␤ be the inverse reaction resistance; then at the electrolyte-solid interface ␤͉⌬V ͉ Ӎ ͉ oxe " oxe ͉. 5 So, as in the previous case, this loss is estimated as…”

Section: ͓6͔mentioning

confidence: 99%

“…Ref. 5,8,9,10 for complete details͒. Because of the assumption that a single rate-determining reaction step occurs at the electrolytesolid interface, the entire diffusion-reaction-conduction process in the porous cathode can be described in terms of two component potentials, the oxidant potential ox and the current potential c…”

Section: Cathodic Structure and Processesmentioning

confidence: 99%

“…5 Recall that the electrical conductivity e is defined by the relationship J ϭ Ϫ e " e ; a similar relationship defines ce , the component ͑electrochemical͒ conductivity: J ϭ Ϫ ce " ce . Also since the relationship between the electrochemical potential for the electron and the electrical potential is e Ϫ ϭ ϪF e , we choose that J ϭ ϪFJ.…”

Section: ͓1͔mentioning

confidence: 99%

“…For lower inlet gas concentrations, electrolyte diffusive transport became more significant. 4 Fehribach et al 5 directly computed the current production in a small 100 ϫ 100 m cathode cross section, and found that on this scale, the diffusive transport in the electrolyte is the greatest contributor to the polarization loss. Kunz and Murphy, 6 on the other hand, suggest that gas-phase diffusional resistance increases with decreasing inlet gas concentrations and accounts for a significant portion of the polarization loss.…”

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confidence: 99%

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Estimates for Polarization Losses in Molten Carbonate Fuel Cell Cathodes

Fehribach

Hemmes

2001

J. Electrochem. Soc.

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This paper compares the polarization losses associated with the various diffusion-reaction-conduction processes in molten carbonate cathodes. The comparisons are made by estimating each type of loss in terms of component electrochemical potentials in joules/mole; this allows diffusive, charge-transfer, and ohmic losses to all be put on equal footing. For characteristic parameter values, diffusion in both the gas and electrolyte phases and conduction in the electrolyte account for similar polarization losses; charge-transfer and conduction in the solid electrode account for significantly smaller losses. These results tend to support and unify the previous work of numerous investigators. Also molecular-channel interactions are found not to contribute significantly to the polarization loss.In recent years, a number of studies have attempted to determine which portion of the overall cathodic process accounts for the majority of polarization losses in molten carbonate fuel cell ͑MCFC͒ cathodes. These studies have resulted in a variety of conclusions, some of which may at first glance appear contradictory. Through ac impedance measurements, Yuh and Selman 1 found that chargetransfer accounts for the majority of the overall polarization loss at lower temperatures ͑600°C͒, while mass transport ͑diffusion͒ and/or slow recombination are more important at higher temperatures ͑700°C͒. Their work does not distinguish the roles of gas-phase and electrolyte-phase transport. Prins et al. 2-4 also made ac impedance measurements; they concluded that for relatively rich inlet gas concentrations, the polarization losses are dominated by ohmic loss ͑electrolyte conduction͒. For lower inlet gas concentrations, electrolyte diffusive transport became more significant. 4 Fehribach et al. 5 directly computed the current production in a small 100 ϫ 100 m cathode cross section, and found that on this scale, the diffusive transport in the electrolyte is the greatest contributor to the polarization loss. Kunz and Murphy, 6 on the other hand, suggest that gas-phase diffusional resistance increases with decreasing inlet gas concentrations and accounts for a significant portion of the polarization loss. Recent work by Peelen et al. 7 found that in particular a carbon dioxide partial pressure below 0.05 atm was detrimental to a MCFC cathode current density of 150 mA/cm 2 .The present work is a brief, but we hope useful, theoretical estimate of the polarization losses in MCFC cathodes; it supports and reinforces many of the conclusions discussed above, and to some extent, unifies them. The estimates are made using the component electrochemical potentials introduced by Fehribach et al. 5,8,9 This formulation is particularly useful here because it allows the various cathodic processes ͑diffusion, conduction, electrochemical reactions͒ to be compared on the same scale ͑i.e., equal footing͒. This work differs from our earlier work 5 in that here we are considering an entire laboratory cathode ͑800 m thick͒ rather than a small cross section, and that ...

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O ₂ ‐reduction at high temperature: MCFC

Hemmes

Selman

2010

Handbook of Fuel Cells

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Oxygen reduction in molten carbonate is discussed in relation to the molten carbonate fuel cell. The melt chemistry of molten carbonate is found to be crucial in understanding the possible reaction mechanism and the dissolution problems of the cathode. Using concepts form linear algebra a complete set of equilibria describing the melt is constructed, which is used to derive the relative concentrations of species in the melt and possible reaction mechanisms. Experimental results are critically reviewed in the light of the theoretical predictions. Based on the obtained insight in the fundamental processes, research directions are indicated for minimizing cathode dissolution and cathode polarization, including a radical new concept of a MCFC with a separate CO 2 channel.

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Cited by 16 publications

References 2 publications

Three-dimensional modeling of polarization characteristics in molten carbonate fuel cells using peroxide and superoxide mechanisms

Three-dimensional modeling of polarization characteristics in molten carbonate fuel cells using peroxide and superoxide mechanisms

Estimates for Polarization Losses in Molten Carbonate Fuel Cell Cathodes

O ₂ ‐reduction at high temperature: MCFC

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Untitled

Cited by 16 publications

References 2 publications

Three-dimensional modeling of polarization characteristics in molten carbonate fuel cells using peroxide and superoxide mechanisms

Three-dimensional modeling of polarization characteristics in molten carbonate fuel cells using peroxide and superoxide mechanisms

Estimates for Polarization Losses in Molten Carbonate Fuel Cell Cathodes

O 2 ‐reduction at high temperature: MCFC

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O ₂ ‐reduction at high temperature: MCFC