On the Predictions of Carbon Deposition on the Nickel Anode of a SOFC and Its Impact on Open-Circuit Conditions

Handle URI:
http://hdl.handle.net/10754/599066
Title:
On the Predictions of Carbon Deposition on the Nickel Anode of a SOFC and Its Impact on Open-Circuit Conditions
Authors:
Lee, W. Y.; Hanna, J.; Ghoniem, A. F.
Abstract:
Previous thermodynamic analyses of carbon formation in SOFCs assumed that graphite could be used to represent the properties of carbon formed in the anode. It is generally observed, however, that catalytically grown carbon nanofibers (CNF) are more likely to form in the SOFC anode with nickel catalysts. The energetic and entropic properties of CNF are different from those of graphite.We compare equilibrium results based on thermochemical properties for graphite, to new results based on a previously reported value of an empirically determined Gibbs free energy for carbon fibers grown on a nickel support (with fitted values of H°CNF = 54.46 kJ/mol and S°CNF = 68.90 J/mol/K for a nickel crystal size of 5.4 nm). There is little difference in predictions of carbon formation under open-circuit conditions between the two carbon types for methane mixtures, with graphite predicted to form at lower temperatures than CNF. There is a much bigger difference in predictions for methanol mixtures, especially at low steam-carbon ratios. The differences for propane are even more pronounced, and the improved predictions assuming CNF are in closer agreement with past observations.We show a strong dependence of CNF formation and "coking threshold" on nickel crystallite size, supporting previous reports that the nickel particle size is a dominating parameter for controlling filament growth. If both carbon types are included in the calculations, only the thermodynamically favored form (i.e., the type having the lowest formation energy) exists. Predicted Nernst potentials are more-or-less independent of the carbon type and in agreement with measured open-circuit voltages. © 2012 The Electrochemical Society.
Citation:
Lee WY, Hanna J, Ghoniem AF (2012) On the Predictions of Carbon Deposition on the Nickel Anode of a SOFC and Its Impact on Open-Circuit Conditions. Journal of the Electrochemical Society 160: F94–F105. Available: http://dx.doi.org/10.1149/2.051302jes.
Publisher:
The Electrochemical Society
Journal:
Journal of the Electrochemical Society
KAUST Grant Number:
KUS-11-010-01
Issue Date:
4-Dec-2012
DOI:
10.1149/2.051302jes
Type:
Article
ISSN:
0013-4651; 1945-7111
Sponsors:
This work has been supported by an award from King Abdullah University of Science and Technology, grant number KUS-11-010-01, and a grant from the Tsinghua-Cambridge-MIT Low Carbon Energy University Alliance.
Appears in Collections:
Publications Acknowledging KAUST Support

Full metadata record

DC FieldValue Language
dc.contributor.authorLee, W. Y.en
dc.contributor.authorHanna, J.en
dc.contributor.authorGhoniem, A. F.en
dc.date.accessioned2016-02-25T13:52:13Zen
dc.date.available2016-02-25T13:52:13Zen
dc.date.issued2012-12-04en
dc.identifier.citationLee WY, Hanna J, Ghoniem AF (2012) On the Predictions of Carbon Deposition on the Nickel Anode of a SOFC and Its Impact on Open-Circuit Conditions. Journal of the Electrochemical Society 160: F94–F105. Available: http://dx.doi.org/10.1149/2.051302jes.en
dc.identifier.issn0013-4651en
dc.identifier.issn1945-7111en
dc.identifier.doi10.1149/2.051302jesen
dc.identifier.urihttp://hdl.handle.net/10754/599066en
dc.description.abstractPrevious thermodynamic analyses of carbon formation in SOFCs assumed that graphite could be used to represent the properties of carbon formed in the anode. It is generally observed, however, that catalytically grown carbon nanofibers (CNF) are more likely to form in the SOFC anode with nickel catalysts. The energetic and entropic properties of CNF are different from those of graphite.We compare equilibrium results based on thermochemical properties for graphite, to new results based on a previously reported value of an empirically determined Gibbs free energy for carbon fibers grown on a nickel support (with fitted values of H°CNF = 54.46 kJ/mol and S°CNF = 68.90 J/mol/K for a nickel crystal size of 5.4 nm). There is little difference in predictions of carbon formation under open-circuit conditions between the two carbon types for methane mixtures, with graphite predicted to form at lower temperatures than CNF. There is a much bigger difference in predictions for methanol mixtures, especially at low steam-carbon ratios. The differences for propane are even more pronounced, and the improved predictions assuming CNF are in closer agreement with past observations.We show a strong dependence of CNF formation and "coking threshold" on nickel crystallite size, supporting previous reports that the nickel particle size is a dominating parameter for controlling filament growth. If both carbon types are included in the calculations, only the thermodynamically favored form (i.e., the type having the lowest formation energy) exists. Predicted Nernst potentials are more-or-less independent of the carbon type and in agreement with measured open-circuit voltages. © 2012 The Electrochemical Society.en
dc.description.sponsorshipThis work has been supported by an award from King Abdullah University of Science and Technology, grant number KUS-11-010-01, and a grant from the Tsinghua-Cambridge-MIT Low Carbon Energy University Alliance.en
dc.publisherThe Electrochemical Societyen
dc.titleOn the Predictions of Carbon Deposition on the Nickel Anode of a SOFC and Its Impact on Open-Circuit Conditionsen
dc.typeArticleen
dc.identifier.journalJournal of the Electrochemical Societyen
dc.contributor.institutionMassachusetts Institute of Technology, Cambridge, United Statesen
kaust.grant.numberKUS-11-010-01en
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