Mixed ionic electronic conductors (MIECs) oxides are used as electrode materials for solid oxide cell (SOC) application, as they combine high electronic conductivity as well as high oxygen diffusivity and oxygen surface exchange coefficients. The ionic transport properties can be directly determined thanks to the isotopic exchange depth profiling (IEDP) method. To date, the reported measurements have been performed at ambient pressure and below. However, for a higher efficiency of hydrogen production at the system level, it is envisaged to operate the cell between 10 and 60 bar. To characterize the MIEC oxides properties in such conditions, an innovative setup able to operate up to a total pressure of 50 bar and 900°C has been developed. The main goal of this study was to compare the behavior of two types of reference materials: the oxygen deficient La-Sr-Fe-Co perovskites, and the overstoichiometric lanthanide nickelates Ln₂NiO_4+δ (Ln = La, Pr, Nd). Diffusion and surface exchange coefficients obtained under 6.3 bar of oxygen are measured and their evolution discussed in light of the change in oxygen stoichiometries. This analysis allows better understanding of the dependency of the surface exchange coefficient with the oxygen partial pressure.

中文翻译：

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高压下的氧扩散和表面交换系数测量：缺氧与超化学计量空气电极材料的比较行为

混合离子电子导体（MIEC）氧化物被用作固体氧化物电池（SOC）应用的电极材料，因为它们结合了高电子电导率以及高氧扩散率和氧表面交换系数。通过同位素交换深度分析 (IEDP) 方法可以直接确定离子传输特性。迄今为止，报告的测量是在环境压力及以下压力下进行的。然而，为了在系统层面实现更高的制氢效率，预计电池在 10 至 60 bar 之间运行。为了表征此类条件下 MIEC 氧化物的特性，我们开发了一种创新装置，能够在高达 50 bar 的总压力和 900°C 的温度下运行。本研究的主要目标是比较两种参考材料的行为：缺氧的 La-Sr-Fe-Co 钙钛矿和超化学计量的镧系镍酸盐Ln ₂ NiO _{4+ δ} (Ln = La, Pr, Nd) 。测量了在 6.3 bar 氧气下获得的扩散系数和表面交换系数，并根据氧化学计量的变化讨论了它们的演变。该分析可以更好地理解表面交换系数与氧分压的依赖性。