Operando XAFS Reveals Dynamic Structural Evolution of Pt Single-Atom Catalysts for Efficient Chlorine...

Metal single-atom catalysts (SACs) with near-100% metal utilization and flexible coordination environments are promising candidates for electrochemical chlorine evolution reaction (CER) to produce valuable Cl₂-a key raw material for plastics manufacturing, water treatment, and pharmaceuticals. However, it remains challenging to assess specific coordination environments for structure-activity relationships and monitor their dynamic structural evolution under catalytic reaction conditions. Herein, operando X-ray absorption fine structure (XAFS) revealed distinct dynamic structural evolution on the low-coordinated Pt site, compared to the conventional PtN₄ site. Specifically, the low-coordinated Pt site transformed into an asymmetry PtN₂Cl₂ structure upon exposure to a Cl^--containing solution, transiently evolved to PtN₂Cl₄ intermediate at low overpotentials, and reverted to PtN₂Cl₂ after CER. By overcoming the limitation of *Cl intermediate coverage on PtN₄ SAC, the low-coordinated Pt SAC displayed superior CER performance to commercial RuO₂ and PtN₄ benchmarks. This work provides new insights into the rational design of coordination geometry in SACs for electrocatalysis.