Owing to its extraordinary high activity for catalysing the oxygen exchange reaction, strontium doped LaCoO3 (LSC) is one of the most promising materials for solid oxide fuel cell (SOFC) cathodes. However, under SOFC operating conditions this material suffers from performance degradation. This loss of electrochemical activity has been extensively studied in the past and an accumulation of strontium at the LSC surface has been shown to be responsible for most of the degradation effects. The present study sheds further light onto LSC surface changes also occurring under SOFC operating conditions. In-situ near ambient pressure X-ray photoelectron spectroscopy measurements were conducted at temperatures between 400 and 790 °C. Simultaneously, electrochemical impedance measurements were performed to characterise the catalytic activity of the LSC electrode surface for O2 reduction. This combination allowed a correlation of the loss in electro-catalytic activity with the appearance of an additional La-containing Sr-oxide species at the LSC surface. This additional Sr-oxide species preferentially covers electrochemically active Co sites at the surface, and thus very effectively decreases the oxygen exchange performance of LSC. Formation of precipitates, in contrast, was found to play a less important role for the electrochemical degradation of LSC.

中文翻译：

---

在SOFC操作条件下La0.6Sr0.4CoO3-δ表面的化学演化及其对电化学氧交换活性的影响。

锶掺杂的LaCoO3（LSC）由于具有极高的催化氧交换反应的活性，因此是用于固体氧化物燃料电池（SOFC）阴极的最有前途的材料之一。但是，在SOFC操作条件下，这种材料的性能会下降。过去已经广泛研究了这种电化学活性的损失，并且已表明锶在LSC表面的积累是造成大多数降解作用的原因。本研究进一步揭示了在SOFC操作条件下也发生的LSC表面变化。在400至790°C之间的温度下进行原位近环境压力X射线光电子能谱测量。同时，进行电化学阻抗测量以表征LSC电极表面对O 2还原的催化活性。这种结合允许电催化活性的损失与在LSC表面上另外的含La的Sr-氧化物种类的出现的相关性。这种额外的Sr-氧化物物种优先覆盖了表面的电化学活性Co位，因此非常有效地降低了LSC的氧交换性能。相反，发现沉淀物的形成对于LSC的电化学降解起较小的作用。这种额外的Sr-氧化物物种优先覆盖了表面的电化学活性Co位，因此非常有效地降低了LSC的氧交换性能。相反，发现沉淀物的形成对于LSC的电化学降解起较小的作用。这种额外的Sr-氧化物物种优先覆盖了表面的电化学活性Co位，因此非常有效地降低了LSC的氧交换性能。相反，发现沉淀物的形成对于LSC的电化学降解起较小的作用。