Nanoscaled La_(0.6)Sr_(0.4)CoO(3-δ) as intermediate temperature solid oxide fuel cell cathode: Microstructure and electrochemical performance

摘要

Lowering the operation temperature of solid oxide fuel cells to the range of 400-600 C has generated new concepts for materials choice, interfacial design and electrode microstructures. In this study nanometer scaled and nanoporous La_(0.6)Sr_(0.4)CoO_(3-δ) (LSC) was derived from metal-organic precursors as thin film cathodes of about 200 nm thickness with mean grain sizes ranging from 17 to 90 nm and porosities of up to 45%. These microstructures resulted from different processing parameters such as heating rate, calcination temperature and post calcination annealing, and made it possible to study the influence of the electrode microstructure on the electrochemical performance. Microstructural characteristics were analyzed by scanning and transmission electron microscopy and the performance was evaluated in terms of area specific polarization resistance by means of electrochemical impedance spectroscopy in a temperature range of 400-600℃ Polarization resistances as low as 0.023 Ωcm~2 were measured at 600℃, facilitated by a substantial increase of the inner surface area of the nanoscaled microstructure, resulting from low temperature processing at <800℃, and by enhanced catalytic properties determined for nanoscaled La_(0.6)Sr_(0.4)Co_(3-δ) prepared by metal organic deposition.