In-depth understanding of electrocatalytically active species transformation during oxygen evolution reaction (OER) is highly guidable to design effective electrocatalysts for water splitting. Herein, cobalt sulfide (CoS_x) nanovesicles decorated with iron sulfide (FeS_x) heterophases were successfully synthesized by using a metal–organic framework precursor through a solvothermal method. The obtained CoS_x/FeS_x exhibited much elevated OER activity as compared to pristine CoS_x and even most previously reported cobalt-based electrocatalysts, with the overpotential of 304 mV at 10 mA cm^–2 in 1 M KOH. As revealed by operando Raman and X-ray absorption spectroscopy measurements, the electrocatalytically active species transformation in CoS_x nanovesicles could be stimulated by the incorporated FeS_x heterophases due to the increased average valence state of cobalt and lowered coordination of cobalt sites. As a result, the electrocatalytically active cobalt oxyhydroxides could be more easily formed on the catalyst surface during OER and thus contributed to the highly improved performance. This real-time spectral and electrochemical insight into the electrocatalytically active species transformation may guide the rational design of highly efficient electrocatalysts for water splitting from the viewpoint of electronic structure-electrocatalytic activity relationship.

中文翻译：

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高效金属电催化氧的过渡金属硫化物中异相刺激的活性物种转化的操作光谱和电化学研究

深入了解氧释放反应（OER）过程中的电催化活性物质的转化对于设计用于水分解的有效电催化剂具有很高的指导意义。在本文中，使用金属-有机骨架前体通过溶剂热法成功合成了以硫化铁（FeS _x）异相修饰的硫化钴（CoS _x）纳米囊泡。与原始CoS _x甚至是以前报道的大多数钴基电催化剂相比，所获得的CoS _x / FeS _x表现出大大提高的OER活性，在10 mA cm ^–2时过电位为304 mV。在1 M KOH中。如操作拉曼和X射线吸收光谱法测量所揭示的，由于钴的平均价态增加和钴位点的配位降低，掺入的FeS _x异相可能会刺激CoS _x纳米囊泡中的电催化活性物质转化。结果，在OER期间可以更容易地在催化剂表面上形成电催化活性的羟基氧化钴，从而有助于高度改善的性能。从电子结构-电催化活性关系的角度，这种对电催化活性物质转化的实时光谱和电化学洞察力可以指导高效的水分解用电催化剂的合理设计。