Intrinsic Activity Identification of Noble Metal Single‐Sites for Electrocatalytic Chlorine Evolution

Abstract Single‐atom catalysts with maximal atom‐utilization have emerged as promising alternatives for chlorine evolution reaction (CER) toward valuable Cl 2 production. However, understanding their intrinsic CER activity has so far been plagued due to the lack of well‐defined atomic structure controlling. Herein, we prepare and identify a series of atomically dispersed noble metals (e.g., Pt, Ir, Ru) in nitrogen‐doped nanocarbons (M 1 −N−C) with an identical M−N 4 moiety, which allows objective activity evaluation. Electrochemical experiments, operando Raman spectroscopy, and quasi‐in situ electron paramagnetic resonance spectroscopy analyses collectively reveal that all the three M 1 −N−C proceed the CER via a direct Cl‐mediated Vomer‐Heyrovský mechanism with reactivity following the trend of Pt 1 −N−C>Ir 1 −N−C>Ru 1 −N−C. Density functional theory (DFT) calculations reveal that this activity trend is governed by the binding strength of Cl*−Cl intermediate (ΔG Cl*−Cl ) on M−N 4 sites (Pt<Ir<Ru) featuring distinct d‐band centers, providing a reliable thermodynamic descriptor for rational design of single metal sites toward Cl 2 electrosynthesis.