Enhanced Oxygen Reduction Reaction Kinetics in Nanocrystalline IT-SOFC Cathodes

BAQUE L.; SOLDATI A.; TROIANI H.E.; SCHREIBER A.; CANEIRO A.; SERQUIS A.

ECS Transactions

Electrochemical Society

Año: 2013 p. 2147 - 2156

1938-6737

Solid oxide fuel cell performance is usually limited by highcathodic area specific resistance (ASR) at intermediatetemperatures (500-700°C). ASR can be decreased by reducingparticle size to nanometer range. This improvement is usuallyascribed to the area/volume ratio increase and a higherconcentration of active sites for the oxygen reduction reaction(ORR). Nevertheless, this solely explanation seems not to beenough for explaining the high electrochemical performance ofsome nanostructured La0.4Sr0.6Co0.8Fe0.2O3-d cathodes previouslyreported (Baqué et al., Electrochemistry Comm. 10 (2008) 1905-1908). Accordingly, the ORR of these cathodes was studied byelectrochemical impedance spectroscopy (EIS) under air and underpure oxygen within the 400-700°C range. The nanostructure wascharacterized even at atomic level by transmission electronmicroscopy (TEM), revealing that the cathode is composed ofnanocrystals surrounded by zones with some degree of crystallinedisorder. These results suggest that this kind of nanostructurefacilitate the ORR in this compound.Introduction