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

Single‐atom catalysts with maximal atom‐utilization have emerged as promising alternatives for chlorine evolution reaction (CER) toward valuable Cl2 production. However, understanding their intrinsic CER activity have 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 (M1–N–C) with an identical M–N4 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 M1–N–C proceed the CER via a direct Cl‐mediated Vomer‐Heyrovský mechanism with reactivity following the trend of Pt1–N–C > Ir1–N–C > Ru1–N–C. Density functional theory (DFT) calculations reveal that this activity trend is governed by the binding strength of Cl*–Cl intermediate (ΔGCl*–Cl) on M–N4 sites (Pt < Ir < Ru) featuring distinct d‐band centers, providing a reliable thermodynamic descriptor for rational design of single metal sites toward Cl2 electrosynthesis.