Developing excellent-performance cathode materials is an inevitable and challenging obstacle in the process of developing practical solid oxide fuel cells, especially in low temperature range. In this paper, we introduce barium into the premium SrCoO-based cathodes and research its consequent effect in the oxygen reduction reaction process. It is observed that the barium dopant could expand the lattice, produce more oxygen vacancies and at some extent reduce the thermal expansion coefficient of parent perovskite, which results from the expanded free space for oxygen migration and weakened Co–O bond by Ba doping. The polarization resistances of single cells with SrBaCoScNbTiO cathodes (x = 0, 0.2 and 0.5, defined as SCSNTi, SBCSNTi and SBCSNTi, correspondingly) are 0.038, 0.025 and 0.016 Ω cm at 600 °C, respectively, and corresponding peak power density of 0.852, 1.054 and 1.217 W cm. The SBCSNTi cathode is selected and it stably operates for 200 h at 550 °C. And it also exhibits excellent performance when CH is used as fuel and good stability for 100 h at 600 °C. First principle calculations prove that the Ba doping effectively reduces the oxygen vacancy formation energy and oxygen migration barrier. This work proves that the lattice expansion effect is an effective strategy for accelerating the oxygen exchange rate and designing high-performance cathode materials.

中文翻译：

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晶格膨胀效应在 SrCoO3 基阴极中的应用，通过 Ba 掺杂提高低温固体氧化物燃料电池的电化学性能

开发性能优异的正极材料是开发实用固体氧化物燃料电池过程中不可避免的且具有挑战性的障碍，特别是在低温范围内。在本文中，我们将钡引入优质 SrCoO 基阴极中，并研究其在氧还原反应过程中的影响。据观察，钡掺杂可以扩大晶格，产生更多的氧空位，并在一定程度上降低母体钙钛矿的热膨胀系数，这是由于Ba掺杂扩大了氧迁移的自由空间并削弱了Co-O键。采用 SrBaCoScNbTiO 阴极（x = 0、0.2 和 0.5，分别定义为 SCSNTi、SBCSNTi 和 SBCSNTi）的单电池在 600 °C 时的极化电阻分别为 0.038、0.025 和 0.016 Ω·cm，相应的峰值功率密度为 0.852 、1.054 和 1.217 W 厘米。阴极选用SBCSNTi，在550℃下稳定运行200h。以CH为燃料时也表现出优异的性能，在600℃下100小时也表现出良好的稳定性。第一原理计算证明Ba掺杂有效降低了氧空位形成能和氧迁移势垒。这项工作证明晶格膨胀效应是加速氧交换速率和设计高性能正极材料的有效策略。