The exact role of defect structure on transition-metal compound for electrocatalytic OER reaction, which is a very dynamic process, remains unclear. Studying the structure-activity relationship of defective electrocatalysts under operando conditions is crucial for understanding their intrinsic reaction mechanism and dynamic behavior of defect sites. Co3O4 with rich oxygen vacancy (VO) has been reported to efficiently catalyze OER. Herein, we constructed pure spinel Co3O4 and VO-rich Co3O4 as catalyst models to study the defect mechanism and investigate the dynamic behavior of defect sites during the electrocatalytic OER process by various operando characterizations. Operando EIS and CV implied that the VO could facilitate the pre-oxidation of the low-valence Co (Co2+, part of which was induced by the VO to balance the charge) at relatively lower applied potential. This observation confirmed that the VO could initialize the surface reconstruction of VO-Co3O4 prior to the occurance of OER process. The quasi-operando XPS and operando XAFS results further demonstrated the oxygen vacancies were filled with OH* firstly for VO-Co3O4 and facilitated pre-oxidation of low-valence Co, and promoted reconstruction/deprotonation of intermediate Co-OOH*. This work provides insight into the defect mechanism in Co3O4 for OER in a dynamic way by observing the surface dynamic evolution process of defective electrocatalysts and identifying the real active sites during the electrocatalysis process. The current finding would motivate the community to focus more on the dynamic behavior of defect electrocatalysts.

中文翻译：

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用于析氧反应的富氧空位 Co3O4 动态行为的操作数识别

缺陷结构对过渡金属化合物在电催化 OER 反应中的确切作用尚不清楚，这是一个非常动态的过程。在操作条件下研究有缺陷的电催化剂的构效关系对于理解它们的内在反应机制和缺陷位点的动态行为至关重要。据报道，具有富氧空位 (VO) 的 Co3O4 可有效催化 OER。在此，我们构建了纯尖晶石 Co3O4 和富含 VO 的 Co3O4 作为催化剂模型，通过各种操作表征来研究缺陷机理并研究电催化 OER 过程中缺陷位点的动态行为。Operando EIS 和 CV 表明 VO 可以促进低价 Co (Co2+, 其中一部分由 VO 诱导以平衡电荷）在相对较低的施加电位下。这一观察证实，VO 可以在 OER 过程发生之前初始化 VO-Co3O4 的表面重建。准原位XPS和原位XAFS结果进一步证明VO-Co3O4的氧空位首先被OH*填充，促进了低价Co的预氧化，促进了中间体Co-OOH*的重建/去质子化。这项工作通过观察有缺陷的电催化剂的表面动态演化过程并确定电催化过程中的真实活性位点，以动态方式深入了解 Co3O4 中用于 OER 的缺陷机制​​。当前的发现将激励社区更多地关注缺陷电催化剂的动态行为。这一观察证实，VO 可以在 OER 过程发生之前初始化 VO-Co3O4 的表面重建。准原位XPS和原位XAFS结果进一步证明VO-Co3O4的氧空位首先被OH*填充，促进了低价Co的预氧化，并促进了中间体Co-OOH*的重建/去质子化。这项工作通过观察有缺陷的电催化剂的表面动态演化过程并确定电催化过程中的真实活性位点，以动态方式深入了解 Co3O4 中用于 OER 的缺陷机制​​。当前的发现将激励社区更多地关注缺陷电催化剂的动态行为。这一观察证实，VO 可以在 OER 过程发生之前初始化 VO-Co3O4 的表面重建。准原位XPS和原位XAFS结果进一步证明VO-Co3O4的氧空位首先被OH*填充，促进了低价Co的预氧化，并促进了中间体Co-OOH*的重建/去质子化。这项工作通过观察有缺陷的电催化剂的表面动态演化过程并确定电催化过程中的真实活性位点，以动态方式深入了解 Co3O4 中用于 OER 的缺陷机制​​。当前的发现将激励社区更多地关注缺陷电催化剂的动态行为。