Fe Nanoclusters Regulate Surface Electronic Structure and Promote Charge Extraction for Enhanced Photocatalytic Degradation Through Heterojunction Engineering in ZnIn ₂ S ₄

Metal nanoclusters provide abundant catalytically active sites and unique electronic structures that are highly beneficial for enhancing photocatalytic performance; however, their practical application is often hindered by poor photostability. Herein, we report a solvothermal strategy to anchor Fe nanoclusters with a size less than 2 nm onto ZnIn 2 S 4 (ZIS) nanosheets via strong Fe–S bonding, thereby addressing this critical limitation and further advancing photocatalytic efficiency. The strong metal‐sulfur interaction not only effectively suppresses the oxidation and leaching of Fe nanoclusters during the photocatalytic process but also induces significant modulation of the surface electronic structure of ZIS. Comprehensive spectroscopic, photoelectrochemical characterizations, and density functional theory (DFT) calculations reveal that the Fe–ZIS heterojunction promotes efficient electron extraction, whereas the directional charge transfer from ZIS to Fe nanoclusters under illumination effectively inhibits the recombination of photogenerated electron–hole pairs. Consequently, the optimized Fe 0.1 –ZIS demonstrates a remarkable increase in photocatalytic degradation rate, effectively breaking down tetracycline under visible light. This work provides valuable insights into the design of stable metal nanocluster‐based photocatalysts.