Enhanced Cr-tolerance of an SOFC cathode by an efficient electro-catalyst coating

摘要

The durability and electro-catalytic activity for oxygen reduction reaction (ORR) of solid oxide fuel cells (SOFCs) cathode often suffer from severe degradation due to poisoning effects such as Cr from interconnectors. Here we report our findings in the development of a Cr-tolerant catalyst, BaCoO3-x (BCO) nano-particles, which can dramatically enhance the ORR activity and durability of a state-of-the-art La0.6Sr0.4Co0.2Fe0.8O3-x (LSCF) cathode exposed to Crofer 22APU. For example, the polarization resistance (R-p) of a bare LSCF cathode increases from similar to 0.4 to similar to 1.5 Omega cm(2) after 100 hs exposure to Cr in air with 3% H2O at 750 degrees C. In contrast, R-p of a BCO-coated LSCF cathode remains to be similar to 0.05 Omega cm(2) under the same condition, suggesting that BCO is catalytically active to ORR but inert to Cr-poisoning. At 700 degrees C, the single cells with the BCO-coated LSCF cathode show an excellent peak power density of similar to 0.514 Wcm(-2) and significantly enhanced durability (degradation rate of 0.086 %h(-1) at 0.8 V), much better than those of cells with a bare LSCF cathode (similar to 0.448 Wcm(-2) and degradation rate of 0.31 % h(-1) at 0.8 V). Raman analysis indicated that the presence of the BCO catalyst coating greatly reduced the amount of Cr accumulated on the cathode surface, thus alleviating the formation of SrCrO4.