Electrochemical carbon dioxide reduction (CORR) to chemicals and fuels is a promising way to alleviate global environmental problems and energy issues. Among the various catalysts, metal-nitrogen-carbon (M–N–C) single-atom catalysts (SACs) have intrigued great excitement in catalysis due to their low cost and high efficiency. However, precisely identifying the active site structure at an atomic level and disclosing the structure-performance relationship remains a grand challenge. In this review, the active structures of the M–N–C catalysts in CORR are first summarized, including isolated metal-N ( = 2, 3, 4, 5) sites, dual-metal centers, and the crucial role of substrates. Subsequently, the role of active structure in changing the adsorption properties of reactants toward CORR is discussed. In particular, the structure-performance relationship and constructive strategies to optimize the CORR pathway are highlighted. Finally, challenges and potential outlooks for the development of M–N–C SACs toward CORR are presented.

中文翻译：

---

深入了解用于电化学 CO2 还原的 M-N-C 单原子催化剂的活性位点

电化学二氧化碳还原（CORR）生产化学品和燃料是缓解全球环境问题和能源问题的一种有前途的方法。在各种催化剂中，金属-氮-碳（M-N-C）单原子催化剂（SAC）由于其低成本和高效率而在催化领域引起了极大的兴趣。然而，在原子水平上精确识别活性位点结构并揭示结构与性能的关系仍然是一个巨大的挑战。在这篇综述中，首先总结了 CO2RR 中 M-N-C 催化剂的活性结构，包括孤立的金属-N (= 2、3、4、5) 位点、双金属中心以及底物的关键作用。随后，讨论了活性结构在改变反应物对 CO2RR 的吸附性能中的作用。特别强调了结构-性能关系和优化 CORR 途径的建设性策略。最后，提出了 M-N-C SAC 朝着 CORR 发展的挑战和潜在前景。