Experimental data on half-cells consisting of YSZ electrolyte pellets and slurry-coated cathodes, and a simplified theoretical model were used to give an insight into the kinetics of oxygen reduction in solid electrolyte composite cathodes. Electrochemical impedance spectroscopy and potentiodynamic polarizations were used to evaluate the main electrochemical parameters of the cathodic process in a temperature range between $500°C$ and $900°C$. The experimental results show that the oxygen reaction is not under activation control at low temperatures, and other phenomena, such as the transfer of oxygen ions to and through the solid electrolyte in the composite cathode, occur and retard the overall rate of oxygen reduction. This working hypothesis was assessed using a simplified theoretical model of the cathode that accounts for charge transfer, mass transfer, and conduction. The model simulations compared satisfactorily with the experimental data, and they show that, at low temperatures, the reaction zone in the cathode is confined to the electrolyte interface. When the temperature is increased, the retarding effects of mass transfer and conduction in the electrolyte become negligible, and the reaction zone progressively extends through the electrode.

1.
Seabaugh
,
M. M.
,
Swartz
,
S. L.
, and
Hasinska
,
K.
, 2003–2007,
Proceedings of the International Symposium on Solid Oxide Fuel Cells
,
S. C.
Sighal
and
M.
Dikiya
, eds.,
The Electrochemical Soc. Inc.
,
New York
, p.
451
.
2.
Huchida
,
H.
,
Suzuki
,
S.
, and
Watanabe
,
M.
, 2003–2007,
Proceedings of the International Symposium on Solid Oxide Fuel Cells
,
S. C.
Sighal
and
M.
Dikiya
, eds.,
The Electrochemical Soc. Inc.
,
New York
, p.
728
.
3.
Barbucci
,
A.
,
Carpanese
,
P.
,
Cerisola
,
G.
, and
Viviani
,
M.
, 2005, “
Electrochemical Investigation of Mixed Ionic/Electronic Cathodes for SOFCs
,”
Solid State Ionics
0167-2738
176
, pp.
1753
1758
.
4.
Winkler
,
J.
,
Hendriksen
,
P. V.
,
Bonanos
,
N.
, and
Mogensen
,
M.
, 1998, “
Geometric Requirements of Solid Electrolyte Cells With a Reference Electrode
,”
J. Electrochem. Soc.
0013-4651
145
, pp.
1184
1192
.
5.
McDonald
,
J. Ross
, ed., 1987,
Impedance Spectroscopy
,
Wiley
, New York, p.
214
.
6.
Esquirol
,
A.
,
Bonanos
,
N.
,
Brandon
,
N.
,
Kilner
,
J.
, and
Mogensen
,
M.
, 2003–2007,
Solid Oxide Fuel Cells
,
S. C.
Sighal
and
M.
Dokiya
, eds.,
The Electrochemical Soc. Inc.
,
New York
, p.
58
.
7.
Ghosh
,
A.
,
Sahu
,
A. K.
,
Gulnar
,
A. K.
, and
Suri
,
A. K.
, 2005, “
Synthesis and Characterization of Lanthanum Strontium Manganite
,”
Scr. Mater.
1359-6462
52
, pp.
1305
1309
.
8.
Costamagna
,
P.
,
Costa
,
P.
, and
Antonucci
,
V.
, 1998, “
Micro-Modelling of Solid Oxide Fuel Cell Electrodes
,”
Electrochim. Acta
0013-4686
43
, pp.
375
394
.
9.
Bard
,
A. J.
and
Faulkner
,
L. R.
, 2001,
Electrochemical Methods
,
Wiley
,
New York
.