Iron‐Modified Biochar Enables Free Radical Switching for Efficient Photofenton Degradation of Trichlorophenol

Efficient removal of chlorophenolic pollutants remains challenging. Iron‐modified biochar shows potential in photo‐Fenton reactions but suffers from iron leaching and activity instability. Herein, Sycamore leaf Heat treat Char (SHC) was modified with ferric nitrate via low‐temperature pyrolysis to construct SHC‐Fe 0.2 with a stable Fe─O─C interface. This composite achieved efficient 2,4,6‐trichlorophenol (TCP) photocatalytic degradation (removal rate 62.84%, photodegradation contribution 47.01%) and low iron leaching (<5%). Iron was stably immobilized as octahedrally coordinated amorphous Fe─O─C, enhancing electron transfer and reactive oxygen species (ROS) generation. Mechanistically, iron modification switched the degradation pathway from nonradical ( 1 O 2 ‐dominated) to radical (•OH, •O 2 − ‐dominated) with a “Fe 2+ /Fe 3+ cycle + surface electron transfer” synergism. This study provides insights for stable iron‐carbon composites and deepens understanding of iron‐carbon interface behavior.