COBALTITES WITH VARIABLE DIMENSIONALITY AS CATHODE MATERIALS FOR
SOFCS
1

N. Preux1, K. Nagasawa2, G. Ehora1, A. Rolle1, H. Nakatsugawa2, S. Daviero-Minaud1, O. Mentré1
UCCS - Unité de Catalyse et de Chimie du Solide - UMR CNRS 8181, ENSCL / UST Lille1, Bâtiment C7a - BP 90 108, 59652 Villeneuve d'Ascq Cedex, France2
Graduate School of Engineering, Yokohama National University,
79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501- Japannicolas.preux@gmail.com

Keywords: new cathode materials, SOFC, cobaltite, dimensionality

Results and Discussion
For this oxide we obtained ASR value as low as 4 Ω.cm2at 770°C, while the Rp(T) shows an Arrhenius behavior
with Ea~1eV (Fig. 2). The electrochemical great timestability is noteworthy, reinforced by the checking that theelectrode resists after 2 months under high temperature
testing and various atmosphere cycling. Our measurements
versus pO2 enable to distinguish complementary
phenomena at the electrode reaction. It also highlights thelimitation of the reaction by charge transfer at the TPB for
this oxide.
70% Ba2Co9O14 - 30% YZS
Ea=1.09eV

0-12Experimental
A systematic experimental procedure [2] has been selectedwith the aim to rationalize our results. It involves several
stages including : theinvestigation of i) theelectrolyte/electrodereactivity, ii) the thermal
behavior iii) the bulk
conductivity measurementsiv) the preparation and thecharacterization
ofsymmetricalcells.
EvenBa2 CoO 6
though several systems arecurrently
underattractive
Co 8O 8 investigations,performances have alreadybeen obtained.
They are detailed in thisabstract for the recentlyevidenced Ba2Co2/3+9O14
oxide [3,4] while ourFig. 1. Ba2 Co 9O 14 structure
presentation
willbeextended to a number of extra-cobaltites. Ba2Co9O14 is thefirst term of the 3D-new series with general formulaBan+1ConO3n+1(Co8O8) [3] (Fig. 1). Its conductivity is 200

S.cm-1 at 650°C. We observed a reversible partial
reducibility on heating (T> 400°C), reminiscent of possible
interesting concentration of vacancies, characteristics ofperovskite. YSZ and CGO has been selected as theelectrolyte materials while electrode/electrolyte composites
have been adjusted for a good adhesion of the electrode.

p (ohm cm )Introduction
Ceramic oxide with 3D-perovskite structure is considered
as an ideal cathode material for intermediate temperaturesolid oxide fuel cell (IT-SOFC). Its versatile structure
enables the adaptation of both cationic and anionicvacancies and a wide range of chemical dopants,
responsible for a mixed electro-anionic conductivity, e.g.
see the promising LnxSr1−xCoyFe1−yO3−δ cobaltites [1]., The
Con+ÆCo(n-1)+ reduction plays in favour of goodelectrocatalytic activity for oxygen reduction through thecreation of oxygen vacancies. However, major obstacles totheir application such as their high thermal expansion
coefficients are to be considered. An alternative approach
would consist on the investigation of various structural
types assorted with particular structural dimensionalities.
In that frame, we have investigated several 1D/2D/3D Cobased oxides without “a priori” about their widely studied
electronic/magnetic particularities intensively studied insolid state physics, e.g. Ba2Co9O14, Ca3Co2O6, Ca3Co4O9,YBaCo2O5, YBaCo4O7.

30%-70%Ea=1.2eV

50%-50%Ea=1.1eV-2-3

Fig. 2. a) SEM picture of the electrode layer b) ASR vs T
for different YSZ/Ba2Co9O14 ratios
Conclusions
The possibility to prepare efficient electrode/electrolyte
systems, using original anisotropic cobaltites (from thestructural point of view) opens a wide field of research,currently under investigation on a number of structuralarchetypes. Here, it is worth announcing the excellent
performances just measured on the 2D- misfit Ca3Co4O9.

References[1] Shuyan L. Et al. , Solid State Ionics 178 (2008) 18531858[2] Ehora G. et al., Chemistry of materials 20 (2008) 74257433[3] Junliang S.et al.. Inorg Mater. 45 (2006) 9151
[4] Ehora G.,et al., Chem. Mater. 19 (2007) 2180.