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Surface reaction and transport in mixed conductors with electrochemically-active surfaces: a 2-D numerical study of ceria

Ciucci, Francesco and Chueh, William C. and Goodwin, David G. and Haile, Sossina M. (2011) Surface reaction and transport in mixed conductors with electrochemically-active surfaces: a 2-D numerical study of ceria. Physical Chemistry Chemical Physics, 13 (6). pp. 2121-2135. ISSN 1463-9076.

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A two-dimensional, small-bias model has been developed for describing transport through a mixed ionic and electronic conductor (MIEC) with electrochemically-active surfaces, a system of particular relevance to solid oxide fuel cells. Utilizing the h-adaptive finite-element method, we solve the electrochemical potential and flux for both ionic and electronic species in the MIEC, taking the transport properties of Sm)(0.15)Ce_(0.85)O_(1.925_ δ) (SDC15). In addition to the ionic flux that flows between the two sides of the cell, there are two types of electronic fluxes: (1) cross-plane current that flows in the same general direction as the ionic current, and (2) in-plane current that flows between the catalytically-active MIEC surface and the metal current collectors. From an evaluation of these fluxes, the macroscopic interfacial resistance is decomposed into an electrochemical reaction resistance and an electron diffusion-drift resistance, the latter associated with the in-plane electronic current. Analysis of the experimental data for the interfacial resistance for hydrogen electro-oxidation on SDC15 having either Pt or Au current collectors (W. Lai and S. M. Haile, J. Am. Ceram. Soc., 2005, 88, 2979–2997; W. C. Chueh, W. Lai and S. M. Haile, Solid State Ionics, 2008, 179, 1036–1041) indicates that surface reaction rather than electron migration is the overall rate-limiting step, and suggests furthermore that the surface reaction rate, which has not been directly measured in the literature, scales with p_(O2)^(-1/4). The penetration depth for the in-plane electronic current is estimated at 0.6 mm for the experimental conditions of interest to SDC15, and is found to attain a value as high as 4 mm within the broader range of computational conditions.

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Haile, Sossina M.0000-0002-5293-6252
Additional Information:© 2010 the Owner Societies. Received 16th July 2010, Accepted 7th September 2010. This work was supported by the Stanford Global Climate Energy Project and the Office of Naval Research under grant N00014-05-1-0712. Additional support was provided by the Gordon and Betty Moore Foundation through the Caltech Center for Sustainable Energy Research and by the National Science Foundation through the Caltech Center for the Science and Engineering of Materials, a Materials Research Science and Engineering Center (DMR-052056). The authors are grateful to Evan Brown for performing image analysis.
Funding AgencyGrant Number
Stanford Global Climate and Energy Project (GCEP)UNSPECIFIED
Office of Naval Research (ONR)N00014-05-1-0712
Gordon and Betty Moore FoundationUNSPECIFIED
Issue or Number:6
Record Number:CaltechAUTHORS:20101206-115505195
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21189
Deposited By: Tony Diaz
Deposited On:13 Dec 2010 19:24
Last Modified:03 Oct 2019 02:20

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