Surface-Modified Zn₃In₂S₆ for a Dual-Pathway Photocatalytic Hydrogen Peroxide Production

Photocatalytic H₂O₂ production via a two-electron oxygen reduction reaction (ORR) represents a green and sustainable alternative to the conventional anthraquinone process for industrial H₂O₂ synthesis. Bimetallic sulfide Zn₃In₂S₆ has emerged as a promising photocatalyst for H₂O₂ production, yet the efficiency remains to be promoted. In this work, we introduced an anionic surfactant, sodium dodecyl sulfate (SDS), into the hydrothermal reactant to achieve a surface-modified Zn₃In₂S₆ with a high photocatalytic H₂O₂ production efficiency. The SDS modification alters the electron state and band alignments and promotes the formation of sulfur vacancies. Consequently, the SDS modification tactic not only enhances charge separation and migration but also switches the reaction pathway from an ORR-dominated route in the pristine Zn₃In₂S₆ to a dual-pathway involving both ORR and water oxidation reaction (WOR). The optimized SDS0.5-Zn₃In₂S₆ photocatalyst achieves a remarkable H₂O₂ production rate of 1066.13 μmol·g^-1·h^-1 in pure water without any sacrificial agents, which is 1.6 times that of the pristine Zn₃In₂S₆. Moreover, under argon atmosphere, it exhibits a H₂O₂ production rate of 598.83 μmol·g^-1·h^-1, approximately three times that of unmodified Zn₃In₂S₆, confirming the enhanced WOR contribution. This work presents a novel Zn₃In₂S₆-based photocatalyst with dual reaction pathways for efficient photocatalytic H₂O₂ production.