Cl − ‐Steered Photo‐Fenton Pathway Reconfiguration on Cu Single‐Atom Sites for High‐Performance Seawater Decontamination

ABSTRACT H 2 O 2 ‐based advanced oxidation processes are promising for water purification, but free‐radical‐dominated pathways are often inhibited by coexisting inorganic anions in high‐salinity environments. Here, we develop a Cu single‑atom doped graphitic carbon nitride nanosheet catalyst and reveal that abundant Cl − in seawater is converted from a potential radical scavenger into an active participant in H 2 O 2 activation. The Cu 1 ‑N 3 /H 2 O 2 /Vis system achieves rapid degradation of 1‑naphthylamine (1‑NA) in seawater, with an apparent rate constant 69 times higher than that of the CN/H 2 O 2 /Vis system. Mechanistic results suggest that Cu 1 ‐N 3 sites promote H 2 O 2 activation and facilitate Cl − ‐involved pathway reconfiguration, leading to the formation of reactive chlorine species (RCS)‐related intermediates, 1 O 2 , and high‐valent Cu‐associated oxidative species. These species collectively establish a cooperative radical/non‐radical oxidation network, rather than a conventional free‐•OH‐dominated pathway. Continuous‐flow tests further demonstrate stable 1‐NA removal during 20 h operation. This work provides a promising strategy for Cl − ‐steered photo‐Fenton pathway reconfiguration toward high‐performance seawater decontamination.