Optimization of Sr content in layered SmBa_(1-x)Sr_xCo_2O_(5+δ) perovskite cathodes for intermediate-temperature solid oxide fuel cells

摘要

Cation ordered perovskites have been recognized as advanced cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). This study focuses on the effects of Sr substitution on crystal characteristics, electrical properties, and electrochemical performance of SmBa_(1-x)Sr_xCo_2O_(5+δ) (x = 0, 0.25, 0.5, 0.75, and 1.0) as an IT-SOFC cathode material. The electrical conductivity improves with increasing Sr content due to the greater amount of electronic holes originated from the increased interstitial oxygen. The area specific resistances (ASRs) of SmBa_(1-x)Sr_xCo_2O_(5+δ) decrease with Sr content up to x = 0.75 and increase abruptly for x = 1. For x = 0.75, the lowest ASR value, 0.138 Ω cm~2, and the highest single cell performance, 1.039 W cm~(-2) at 600 ℃, are obtained. These results indicate that SmBa_(1-x)Sr_xCo_2O_(5+δ) is optimized at x = 0.75 in terms of obtaining the best performance for IT-SOFCs.