Chitin Biomass Enriches Atomically Dispersed Fe Sites on Carbon Dots for pH Adaptive and Regenerative Solar Light Fenton Catalysis

Abstract Photo-Fenton reactions have attracted significant interest for water decontamination, but their practical application is limited by iron (Fe) aggregation and narrow pH windows. Precursor chemistry plays a critical yet underexplored role in regulating the spatial distribution and catalytic accessibility of iron in carbon-based photo-Fenton catalysts. Manipulation of Fe sites distribution to tune catalytic accessibility of Fe on carbon dots (CDs) constitutes a topic of vast interest and a challenging pursuit. Here, we report a precursor-directed strategy to develop Fe atomically surface-accessible CDs (Fe-SACDs), with excellent response to simulated solar light, using shrimp-extracted chitin as a precursor. A controlled spatial distribution of atomically dispersed Fe centers was enabled by the abundant nitrogen- and oxygen-containing functional groups in the chitin precursor. The surface-accessible Fe species enabled robust Fe(II)/Fe(III) cycling, which enhances the generation of reactive species for catalysis of organics in water. These advantages afforded highly efficient degradation of methylene blue (∼100% removal) with improved structural stability (more than 5 cycles) and broader pH adaptability (3–12) compared to nonsurface-accessible controls where Fe is absent (CDs) or not atomically dispersed (Fe-CDs). This study reveals how a precursor-directed control of Fe spatial distribution governs the performance of photo-Fenton catalysis, inspiring a new strategy for designing efficient biomass-derived carbon catalysts for advanced water decontamination.