Hyperstoichiometric La1.9Sr0.1NiO4+δ Mixed Conductor as Novel Cathode for Intermediate Temperature Solid Oxide Fuel Cells

[+] Author and Article Information
A. Aguadero, M. Pérez

 CIEMAT, Av. Complutense 22, E-28040 Madrid, Spain

M. J. Escudero

 CIEMAT, Av. Complutense 22, E-28040 Madrid, Spainm.escudero@ciemat.es

J. A. Alonso

 Instituto de Ciencia de Materiales de Madrid (CSIC), Campus Cantoblanco, E-28049 Madrid, Spain

L. Daza

 CIEMAT, Av. Complutense 22, E-28040 Madrid, Spain; Instituto de Catálisis y Petroleoquímica (CSIC), Campus Cantoblanco, E-28049 Madrid, Spain

J. Fuel Cell Sci. Technol 4(3), 294-298 (Jun 08, 2006) (5 pages) doi:10.1115/1.2743075 History: Received December 12, 2005; Revised June 08, 2006

The materials La2xSrxNiO4+δ(x=0,0.1) with K2NiF4 structure have been studied in order to explore their potential use as cathodes for intermediate temperature solid oxide fuel cells. The introduction of Sr in the La2NiO4+δ lattice produces an enhancement of the electric conductivity but is accompanied by a decrease of ionic transport species. Neutron powder diffraction data show a transition from orthorhombic to tetragonal symmetry with the incorporation of Sr in the LaO sublattice. Excess oxygen determined by iodometric titration shows that strontium insertion generates a decrease of the interstitial oxygen. In order to avoid the concomitant decrease of the ionic conductivity, the system underwent heat treatments under high oxygen pressure (200bar, 650°C). As a result, the O2 treated La1.9Sr0.1NiO4+δ exhibited an increase of the amount of interstitial oxygens (δ=0.17) but with improved electronic properties. The polarization resistances measured for these materials vary between 8Ωcm2 and 0.1Ωcm2 in air at the temperature range of 700975°C. This remarkable behavior enables us to propose this material as an alternative cathode for IT-SOFC.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Crystal structure of La2NiO4+δ.: O(1) are equatorials atoms of the NiO6 octaedra whereas O(2) and O(3) are the axial oxygens

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Figure 2

Observed (circles), calculated (full line), and difference (bottom) NPD Rietveld profiles at room temperature for La1.9Sr0.1NiO4+δ refined in the F4/mmm space group. The series of tick marks corresponds to the allowed Bragg reflections.

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Figure 3

Electrical conductivity for La2NiO4+δ and La1.9Sr0.1NiO4+δ (raw and treated at 650°C under pO2=200bar) in air at different temperatures

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Figure 4

Impedance spectra measured for LaNiO4+δ cathode on 8YSZ in air at different temperatures: (a)500–600°C; (b)650–750°C; (c)800–900°C; and (d)950–975°C

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Figure 5

Interfacial polarization resistance measured in air at different temperatures for LaNiO4+δ cathode on 8YSZ and La1.9Sr0.1NiO4+δ cathode on 8YSZ



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