Chemical compatibility and electrochemical property of intermediate-temperature SOFC cathodes under Cr poisoning condition

Abstract

We have investigated the relationship between the chemical compatibility and electrochemical properties of La 0.6Sr 0.4Fe 0.8Co 0.2O 3 (LSCF), LaNi 0.6Fe 0.4O 3 (LNF), and La 0.8Sr 0.2MnO 3 (LSM) as a cathode against the Cr poisoning condition. Powder mixtures of LSCF–Cr 2O 3, LSM–Cr 2O 3, and LNF–Cr 2O 3 were heated at 1073 K and analyzed by X-ray powder diffraction with the Rietveld refinement. It was found that LNF powder was less reactive with Cr 2O 3 than LSCF and LSM powder from the viewpoint of the consumption of Cr 2O 3 in the mixtures. From electrochemical measurement, it was found that the cathodic overvoltage was almost unchanged for cells with LNF cathode, either in the presence or absence of a Cr-containing alloy. On the other hand, the cells with LSCF and LSM cathode in the presence of the alloy exhibited a steep increase in the overvoltage curve. These results show that LNF cathode is more stable against Cr poisoning than the other two cathodes. Therefore, we expect LNF to be a long-life cathode with high stability against Cr poisoning in solid oxide fuel cell because of the low reactivity of LNF with Cr 2O 3.