PubMed2003
A one-pot, soft-chemistry, surfactant-assisted co-assembly approach to prepare La(1-x)Sr(x)MnO(3) (LSM)/Y(2)O(3)-stabilized ZrO(2) (YSZ) nanocomposites for use as solid oxide fuel cell (SOFC) cathodes has been investigated. This material with sub-hundred nanometer grain sizes for each phase is the first such nanocomposite where aqueous-based precursors of each component are incorporated in a single synthetic step. This approach utilizes the co-assembly of an anionic yttrium/zirconium acetatoglycolate gel, cetyltrimethylammonium bromide as the cationic surfactant template, and inorganic La, Mn, and Sr salts under alkaline aqueous conditions. The resulting as-synthesized product is an amorphous mesostructured organic/inorganic composite, which is transformed to a mesoporous inorganic oxide with nanocrystalline YSZ walls upon calcination. Calcination to temperatures above 600 degrees C lead to collapse of the mesopores followed by further crystallization of the nanocrystalline YSZ phase and a final crystallization of the LSM perovskite phase above 1000 degrees C. Both the fully crystalline LSM/YSZ and the mesoporous intermediate phase have been investigated for phase homogeneity by TEM energy-dispersive X-ray spectroscopy (EDX) mapping and spot analysis which confirm the dispersion of LSM within a YSZ matrix at the nanometer scale. Impedance spectroscopy analysis of LSM/YSZ nanocomposite electrodes demonstrate a low polarization resistance of around 0.2 omega cm(2) with an activation energy (E(a)) as low as 1.42 eV. Cathodic polarization studies show stable current densities over a 40 h test demonstration.