Morphologically architectured spray pyrolyzed lanthanum ferrite-based cathodes-A phenomenal enhancement in solid oxide fuel cell performance

摘要

Nanocrystalline single phase La_(1-x)Sr_xCo_(1-x)Fe_yO_(3-δ) [LSCF] (0 ＜ x ≤ 0.5, y = 0.2, 0.8) based cathodes (crystallite size 30-50 nm) are synthesized by two fluid spray-pyrolysis (SP) for solid oxide fuel cell (SOFC) application. The particulate sizes of the synthesized cathodes are found to be in the range of 100 -200 nm. Particulate morphology of highest conducting cathode (～1500 S cm~(-1)) is tailored using homomolecular seeding agent of precalcined pyrolyzed ashes. Interfacial polarizations of the such SP synthesized screen printed cathodes onto gadolinium doped ceria (CCO) based electrolyte are found to be much lower (0.032-0.16 Ω cm~2 at 800 ℃-500 ℃) with highest exchange current density (～722 mA cm~(-2) at 800 ℃) for oxygen reduction reaction. Enhanced current density of 4.0 A cm(-2) (0.7 V, 800 ℃) is obtained for SOFC button cells using optimized LSCF cathode with hydrogen as fuel and air as oxidant. LSCF cathodes synthesized by spray pyrolysis using homomolecular seeding exhibit interconnected mesoporosity having primary nano-particulates embedded within. Endurance test of button cells till 500 h results low degradation viz. 3.8% and 8.9% 1000 h~(-1) with electronic loads of 0.5 A cm~(-2) and 1.0 A cm~(-2) respectively. High performances of such cells are clinically correlated with SP processing conditions and particulate morphology of cathode powders.