Incorporating rare-earth samarium into MnIn ₂ S ₄ micron flowers for visible-light-driven H ₂ O ₂ generation and organic pollutant degradation

Metal chalcogenide semiconductors show promise for energy conversion and environmental remediation due to their visible-light responsiveness, yet rapid recombination of photogenerated electron-hole pairs limits their practical efficiency. Here, a series of samarium (Sm)-doped MnIn₂S₄ photocatalysts were synthesized via a one-pot hydrothermal method and systematically explored, and it was found that Sm³⁺ incorporation modulates their structure and photocatalytic performance. Among them, 5% Sm-doped MnIn₂S₄ exhibits superior activity, achieving a H₂O₂ production rate of 143 μmol g⁻¹ h⁻¹-1.5 times higher than that of the undoped material-and degrading methylene blue with an 89% efficiency and a reaction rate 1.6-fold faster than that of the pristine phase. Mechanistic studies reveal that superoxide radicals (˙O₂⁻) dominate the photocatalytic process, with H₂O₂ formation proceeding via a two-electron oxygen reduction pathway. These findings demonstrate an effective strategy for enhancing metal chalcogenides with rare-earth doping and provide guidance for the design of high-performance inorganic photocatalysts.