Abstract：
Nickel/yttria-stabilized zirconia (YSZ) composites are the most commonly used fuel electrodes for solid oxide cells. While microstructural changes of Ni/YSZ during operational conditions have been thoroughly investigated, there is limited knowledge regarding Ni/YSZ surface chemistry under working conditions. In this study, we examine the interaction between Ni/YSZ electrodes and water vapor under open circuit and polarization conditions, utilizing near ambient pressure soft and hard X-ray photoelectron spectroscopies. Miniature cells with conventional porous Ni/YSZ composite cermet cathodes were modified to facilitate the direct spectroscopic observation of the functional electrode\'s areas close to the interface with the YSZ electrolyte. The results highlight dynamic changes in the oxidation state and composition of Ni/YSZ under H2 and H2O atmospheres. We also quantify the accumulation of impurities on the electrode surface. Through adjustments in the pretreatment of the cell, the correlation between the nickel surface oxidation state and the cell\'s electrochemical performance during H2O electroreduction is established. It is unequivocally shown that nickel surface oxidation in H2O electrolysis favors NiO over Ni(OH)x, providing critical insights into the mechanism of Ni-phase redistribution within the electrode during long-term operation. Depth-dependent photoemission measurements, combined with theoretical quantitative simulations, reveal that NiO and Ni phases are uniformly mixed on the surface during H2O electrolysis. This differs from the conventional expectation of a NiO-shell/Ni-core configuration in gas phase oxidation. These findings provide crucial insights into the surface chemistry of Ni/YSZ electrodes under conditions relevant to H2O electrolysis, elucidating their impact on the electrochemical performance of the cell.
摘要：
镍/氧化钇稳定的氧化锆（YSZ）复合材料是固体氧化物电池最常用的燃料电极。虽然Ni/YSZ在运行条件下的微观结构变化已经被彻底研究，在工作条件下，有关Ni/YSZ表面化学的知识有限。在这项研究中,我们研究了在开路和极化条件下Ni/YSZ电极与水蒸气之间的相互作用，利用近环境压力软和硬X射线光电子能谱。对具有常规多孔Ni/YSZ复合金属陶瓷阴极的微型电池进行了改性，以促进对功能电极与YSZ电解质界面附近区域的直接光谱观察。结果突出了H2和H2O气氛下Ni/YSZ的氧化态和组成的动态变化。我们还量化了杂质在电极表面上的积累。通过调整细胞的预处理，建立了H2O电还原过程中镍表面氧化态与电池电化学性能之间的相关性。明确表明，H2O电解中的镍表面氧化比Ni（OH）x更有利于NiO，提供关键的见解，在长期操作期间电极内的Ni相重新分布的机制。依赖于深度的光发射测量，结合理论定量模拟，结果表明，在H2O电解过程中，NiO和Ni相在表面均匀混合。这不同于气相氧化中NiO-壳/Ni-核结构的常规预期。这些发现为在与H2O电解相关的条件下Ni/YSZ电极的表面化学提供了重要的见解。阐明它们对电池电化学性能的影响。
