YBaCo2O5+δ-based double-perovskite cathodes for intermediate-temperature solid oxide fuel cells with simultaneously improved structural stability and thermal expansion properties

The poor structural stability and high thermal expansion coefficient of YBaCo2O5+delta (YBCO) cathode seriously impede its practical application in intermediate-temperature solid oxide fuel cells (IT-SOFCs). Herein, single- and double-doped YBaCoCuO5+delta (YBCC), YBaCoFeO5+delta (YBCF) and YBaCo2/3Fe2/3Cu2/3O5+delta (YBCFC) are comparatively studied to assess the influences of doping strategy on stability, thermal and chemical compatibilities. The improvement of structural stability and thermal expansion properties of YBCO is achieved simultaneously by the Fe or/and Cu doping in Co-site. First-principles calculations further confirm that the substitution of Fe or/and Cu for Co improve the structural stability compared to undoped YBCO. The YBCC and YBCFC exhibit good thermal and chemical compatibility with La0.9Sr0.1Ga0.8Mg0.2O3-delta (LSGM) electrolyte below 950 degrees C. Moreover, the YBCC cathode displays better electro-catalytic activity in the studied cathodes, in which the area specific resistance is 0.138 Omega cm(2) at 700 degrees C. The YBCC cathode shows good electrochemical stability over a 20-h test period. The Cu-doped YBCC double perovskite has stable structure and excellent thermal and chemical compatibility, making it a good cathode candidate for IT-SOFCs. Our findings provide a promising strategy to simultaneously improve structural stability and thermal expansion properties in Co-based perovskites, thus greatly extending their applications. (C) 2018 Elsevier Ltd. All rights reserved.