Nuclear forward scattering (NFS) is a synchrotron-based technique relying on the recoil-free nuclear resonance effect similar to Mössbauer spectroscopy. In this work, we introduce NFS for in situ and operando measurements during electrocatalytic reactions. The technique enables faster data acquisition and better discrimination of certain iron sites in comparison to Mössbauer spectroscopy. It is directly accessible at various synchrotrons to a broad community of researchers and is applicable to multiple metal isotopes. We demonstrate the power of this technique with the hydrogen evolution mechanism of an immobilized iron porphyrin supported on carbon. Such catalysts are often considered as model systems for iron–nitrogen-carbon (FeNC) catalysts. Using in situ and operando NFS in combination with theoretical predictions of spectroscopic data enables the identification of the intermediate that is formed prior to the rate-determining step. The conclusions on the reaction mechanism can be used for future optimization of immobilized molecular catalysts and metal–nitrogen–carbon (MNC) catalysts.

中文翻译：

---

应用核前向散射作为原位和操作工具来表征析氢反应中的 FeN4 部分

核前向散射 (NFS) 是一种基于同步加速器的技术，依赖于类似于穆斯堡尔光谱的无反冲核共振效应。在这项工作中，我们引入了 NFS，用于电催化反应期间的原位和操作测量。与穆斯堡尔光谱法相比，该技术能够更快地采集数据并更好地区分某些铁位点。广泛的研究人员可以在各种同步加速器上直接使用它，并且适用于多种金属同位素。我们通过碳负载的固定铁卟啉的析氢机制展示了该技术的威力。此类催化剂通常被视为铁氮碳（FeNC）催化剂的模型系统。将原位和操作NFS 与光谱数据的理论预测相结合，能够识别在速率确定步骤之前形成的中间体。反应机理的结论可用于未来固定化分子催化剂和金属氮碳（MNC）催化剂的优化。