Insights into the durability of Co-Fe spinel oxygen evolution electrocatalysts via operando studies of the catalyst structure
Insights into the durability of Co-Fe spinel oxygen evolution electrocatalysts via operando studies of the catalyst structure
复制标题
DOI：
10.1039/c7ta10892c
复制
发表时间：
2018-04-28
影响因子：
11.9
通讯作者：
Granozzi, G.
中科院分区：
文献类型：
--
作者：
Calvillo, L.;Carraro, F.;Granozzi, G.
用原位X射线光电子能谱(XPS)和操纵面X射线吸收谱(XAS)研究了Co-Fe尖晶石在析氧操作条件下的元素重组和关键活性中心的氧化态变化。这两种技术的结合可以识别氧化物的表面和本体修饰，并将它们与延长循环期间的活性损失联系起来。结果表明，在析氧反应(OER)条件下，Co-Fe尖晶石经历了表面不可逆的相演化，形成了由新的稳定的Co(III)和Fe(III)物种组成的非晶层。加速老化试验表明，耐久性，即循环处理过程中的性能损失，与尖晶石的结构/化学稳定性没有直接关系，而与由于电化学功而在表面形成的新物种有关。因此，经历了较大变化的材料也是最耐用的材料，这表明了解材料在催化过程中的化学和/或结构演变可能是设计高活性和稳定催化剂的关键。
Elemental reorganisation and oxidation state changes of key active sites in Co-Fe spinels are investigated by in situ X-ray photoemission spectroscopy (XPS) and operando X-ray absorption spectroscopy (XAS) under oxygen evolution operating conditions. The combination of the two techniques allows identifying both the surface and bulk modifications on the oxides and relating them to the activity loss during extended cycling. The results show that Co-Fe spinels experience a surface irreversible phase evolution under oxygen evolution reaction (OER) conditions, resulting in the formation of an amorphous layer composed of new stable Co(iii) and Fe(iii) species. Accelerated ageing tests show that the durability, intended as the performance loss during cycling treatments, is not directly related to the structural/chemical stability of the spinels but to the new species formed at the surface due to the electrochemical work. Thus, the material that experienced more significant changes was also the most durable one, demonstrating that the understanding of the chemical and/or structural evolution of the materials during the catalytic process can be the key for the design of highly active and stable catalysts.