Transition‐Metal‐Doped ZnIn ₂ S ₄ Photocatalysts for Enhanced Solar Hydrogen Production

Sustainable energy relies on developing reliable and efficient photocatalysts for solar‐powered hydrogen production. Zinc indium sulfide (ZnIn 2 S 4 , ZIS) has a favorable bandgap and can absorb visible light; however, its photocatalytic efficiency is limited by rapid charge carrier recombination and limited active site accessibility. This work aims to improve ZIS's photocatalytic efficiency by incorporating iron (Fe 3 + ) doping and engineering its morphology. A straightforward hydrothermal method produced flower‐like hierarchical Fe‐doped ZIS photocatalysts. The Fe 3 + ions enhanced charge separation by altering the electrical structure of ZIS and creating beneficial defect sites. Doping and the well‐defined, flower‐like shape, which increase the surface area and reactive sites for photocatalysis, were confirmed through structural and optical characterizations. Photocatalytic hydrogen evolution tests showed improved performance with optimized Fe‐doped ZIS, reaching 5489 µmol·g − 1 ·h − 1 compared to 1422 µmol·g − 1 ·h − 1 for pure ZIS under visible light. The hierarchical structure and Fe doping, which improve light harvesting and charge dynamics, are responsible for this enhancement. This study shows that transition‐metal doping and morphological design can boost ZIS's photocatalytic activity in a scalable way. These findings highlight materials with high performance for solar hydrogen production, supporting progress towards more sustainable energy solutions.