Microstructure optimization for high-performance PrBa_(0.5)Sr_(0.5)Co_(1.5)Fe_(0.5)O_(5+δ~-)-La_2NiO_(4+δ) core-shell cathode of solid oxide fuel cells

摘要

Four PrBa0.5Sr0.5Co1.5Fe0.5O5+delta (PBSCF)-La2NiO4+delta (LN) core-shell cathodes, designated as PL-0, PL-1, PL-3 and PL-5, are prepared by infiltrating LN solution into PBSCF scaffold, and they are investigated in terms of the effect of LN thickness on their electrochemical performance. PL-3 with a continuous LN coating of a moderate average thickness (similar to 9 nm) demonstrates the lowest initial polarization resistance (0.51 Omega cm(2)) and highest power density (0.71 W cm(-2)) among all the cathodes. Polarized at 400 mA cm(-2) and 700 degrees C for up to 40 h, the polarization resistance of all the prepared cathodes increases to approach a stable level after early stage decrease due to current activation, and PL-3 exhibits a slower average rate of performance degradation (25%). The electrochemical performance improvement is mainly attributed to that LN has a relatively high oxygen surface exchange coefficient and continuous LN coating depresses Sr segregation at PBSCF/LN interface.