Identification of catalytically active sites at solid/liquid interfaces under reaction conditions is an essential task to improve the catalyst design for sustainable energy devices. Electrochemical scanning tunneling microscopy (EC‐STM) combines the control of the surface reactions with imaging on a nanoscale. When performing EC‐STM under reaction conditions, the recorded analytical signal shows higher fluctuations (noise) at active sites compared to non‐active sites (noise‐EC‐STM or n‐EC‐STM). In the past, this approach has been proven as a valid tool to identify the location of active sites. In this work, the authors show that this method can be extended to obtain quantitative information of the local activity. For the platinum(111) surface under oxygen reduction reaction conditions, a linear relationship between the STM noise level and a measure of reactivity, the turn‐over frequency is found. Since it is known that the most active sites for this system are located at concave sites, the method has been applied to quantify the activity at steps. The obtained activity enhancement factors appeared to be in good agreement with the literature. Thus, n‐EC‐STM is a powerful method not only to in situ identify the location of active sites but also to determine and compare local reactivity.

中文翻译：

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通过电化学扫描隧道显微镜对局部电催化活性进行原位量化

在反应条件下识别固/液界面处的催化活性位点是改进可持续能源装置催化剂设计的一项重要任务。电化学扫描隧道显微镜 (EC-STM) 将表面反应的控制与纳米级成像相结合。在反应条件下执行 EC-STM 时，与非活性位点（噪声-EC-STM 或 n-EC-STM）相比，记录的分析信号在活性位点显示出更高的波动（噪声）。过去，这种方法已被证明是识别活动站点位置的有效工具。在这项工作中，作者表明该方法可以扩展以获得当地活动的定量信息。对于氧还原反应条件下的铂（111）表面，STM 噪声水平与反应性测量之间的线性关系，发现了翻转频率。由于已知该系统最活跃的位点位于凹形位点，因此该方法已应用于量化步长的活动。获得的活性增强因子似乎与文献非常吻合。因此，n-EC-STM 是一种强大的方法，不仅可以原位识别活性位点的位置，还可以确定和比较局部反应性。