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

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.