Gadolinium-Vacancy Clusters in the (111) Surface of Gadolinium-Doped Ceria: A Density Functional Theory Study
Gadolinium-Vacancy Clusters in the (111) Surface of Gadolinium-Doped Ceria: A Density Functional Theory Study
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DOI：
10.1021/acs.chemmater.5b02861
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发表时间：
2015-12-08
影响因子：
8.6
通讯作者：
de Leeuw, Nora H.
中科院分区：
文献类型：
--
作者：
Aparicio-Angles, Xavier;Roldan, Alberto;de Leeuw, Nora H.
固体氧化物燃料电池是一种很有前途的可持续发电设备。电解液材料在连接阳极和阴极中起着重要的作用，影响着器件的性能。在此背景下，GdC已被证明是一种有效的电解液材料，尽管掺杂团簇的存在会降低其效率。使用后，掺杂团簇开始出现在位错、位错、晶界或表面。因此，在这些区域附近的原子水平上研究掺杂团簇就变得至关重要，因为它可以让我们了解这一现象发生的原因以及它对氧传导的影响。在此背景下，本论文研究了掺杂在(111)GDC表面附近聚集的影响。我们研究了材料中两种不同的Gd浓度，约为7%和14%，接近10%的最佳浓度。我们的结果表明，表面弛豫是决定缺陷团簇在表面上的偏好的关键因素。我们还计算了不同缺陷团簇在不同温度下的相对丰度，包括组态熵项。结果表明，在650-1100K的工作温度范围内，不同团簇结构的相对丰度不同，表明在高浓度下，择优掺杂团簇类似于Gd2O3的结构，表明形成了Gd_2O_3微区。最后，我们发现氧的扩散将受到这些磁区的形成的影响。通过评估氧的迁移率，我们得出结论，氧空位将被表面的Gd团簇捕获。这些空位陷阱阻止氧扩散，从而对材料和燃料电池的总体性能产生负面影响。
Solid-oxide fuel cells are promising devices for sustainable power generation. Electrolyte materials play an important role in connecting the anode and cathode, and they influence the performance of the device. In this context, gadolinium-doped ceria (GDC) has proven to be an efficient electrolyte material, although the presence of dopant clusters can lower its efficiency. After usage, dopant clusters start appearing at dislocations, translocations, grain boundaries, or surfaces. Hence, the study of dopant clustering at the atomic level near these regions becomes of vital importance, as it allows us to understand the reasons for the occurrence of this phenomenon and its impact on the oxygen conduction. In this context, the present paper studies the impact of dopant clustering near the (111) GDC surface. We have studied two different gadolinium concentrations in the material, of approximately 7% and 14%, which are close to the optimum concentration of 10%. Our results indicate that surface relaxation is a key factor in determining the preference of defect clusters to be found in the surface. We have also calculated the relative abundance of different defect clusters at different temperatures, including the configurational entropy term. It was revealed that working temperatures (650-1100 K) show the relative abundance of different cluster structures, displaying that, at high concentrations, preferred dopant clusters resemble the structure of Gd2O3, showing the formation of gadolinia domains. Finally, we show that oxygen diffusion will be affected by the formation of these domains. After evaluating the oxygen mobility, we conclude that oxygen vacancies will be trapped by the gadolinium clusters at the surface. These vacancy traps prevent oxygen diffusion, thereby affecting negatively the performance of the material and the fuel cell in general.