Hesse Fabian, da Silva Ivan, Bos Jan-Willem G
Institute of Chemical Sciences, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K.
ISIS Facility, Rutherford Appleton Laboratory, Harwell Oxford, Didcot OX11 0QX, U.K.
JACS Au. 2024 Apr 2;4(4):1538-1549. doi: 10.1021/jacsau.4c00049. eCollection 2024 Apr 22.
Layered LnBaCoO perovskites are important mixed ionic-electronic conductors, exhibiting outstanding catalytic properties for the oxygen evolution/reduction reaction. These phases exhibit considerable structural complexity, in particular, near room temperature, where a number of oxygen vacancy ordered superstructures are found. This study uses bond valence site energy calculations to demonstrate the key underlying structural features that favor facile ionic migration. BVSE calculations show that the 1D vacancy ordering for Ln = Sm-Tb could be beneficial at low temperatures as new pathways with reduced barriers emerge. By contrast, the 2D vacancy ordering for Ln = Dy and Y is not beneficial for ionic transport with the basic layered parent material having lower migration barriers. Overall, the key criterion for low migration barriers is an expanded plane, supported by Ba, coupled to a small Ln size. Hence, Ln = Y should be the best composition, but this is stymied by the low temperature 2D vacancy ordering and moderate temperature stability. The evolution of the oxygen cycling capability of these materials is also reported.
层状LnBaCoO钙钛矿是重要的混合离子-电子导体，对析氧/氧还原反应表现出优异的催化性能。这些相表现出相当大的结构复杂性，特别是在接近室温时，会发现许多氧空位有序的超结构。本研究使用键价位点能量计算来证明有利于离子轻松迁移的关键潜在结构特征。键价位点能量计算表明，对于Ln = Sm-Tb，一维空位有序在低温下可能是有益的，因为会出现具有更低势垒的新路径。相比之下，对于Ln = Dy和Y的二维空位有序不利于离子传输，因为基本的层状母体材料具有更低的迁移势垒。总体而言，低迁移势垒的关键标准是由Ba支撑的扩展平面与较小的Ln尺寸相结合。因此，Ln = Y应该是最佳组成，但这受到低温二维空位有序和中等温度稳定性的阻碍。还报道了这些材料的氧循环能力的演变。
