Highly active La0.4Sr0.6Co0.8Fe0.2O3
d nanocatalyst for oxygen reduction in intermediate temperature-solid oxide fuel cells

C. CHANQUIA; L. MOGNI; H. TROIANI; A. CANEIRO

JOURNAL OF POWER SOURCES

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2014 vol. 270 p. 457 - 467

0378-7753

Pure-phase La0.4Sr0.6Co0.8Fe0.2O3d (LSCF) nanocrystallites were successfully synthesized by the combustionmethod, by employing glycine as fuel and complexing agent, and ammonium nitrate as combustiontrigger. The morphological and structural characterization of the LSCF nanopowders wasperformed by using X-ray diffraction, N2 physisorption and electron microscopy. The LSCF nanopowderconsists of interconnected nanocrystallites (~45 nm) forming a sponge-like structure with meso andmacropores, being its specific surface area around 10 m2 g1. Crystalline structural analyses show thatthe LSCF nanopowder presents cubic symmetry in the Pm-3m space group. By employing the spincoating technique and different thermal treatments, symmetrical cells with different electrode crystallitesize (45 and 685 nm) were built, by using La0.8Sr0.2Ga0.8Mg0.2O3d as electrolyte. Electrochemicalimpedance spectroscopy measurements were performed varying temperature and pO2. The area specificresistance of the nanostructured sample (45 nm) decreases by two orders of magnitude with respect tothe submicrostructured sample (685 nm), reaching values as low as 0.8 U cm2 at 450 C. Thisimprovement is attributed to the cathode morphology optimization in the nanoscale, i.e., enlargement ofthe exposed surface area and shortening of the oxygen diffusion paths, which reduce the polarizationresistance associated to the surface exchange and O-ion bulk diffusion process.