Precise Regulation of Zn, S Dual Vacancies in Zn ₃ In ₂ S ₆ Inducing Local Orientated Electrical Field for Photocatalytic H ₂ O ₂ Generation

Photocatalytic H₂O₂ synthesis attracts interest for solar-to-fuel conversion but suffers from low carrier utilization and sluggish kinetics. Herein, we present a confinement strategy to precisely regulate Zn and S vacancies (V_Zn, V_S) in Zn₃In₂S₆ for photocatalytic H₂O₂ generation. ZnSO₄, InCl₃, thioacetamide, and cetyltrimethylammonium bromide (CTAB) were utilized to synthesize Zn₃In₂S₆ via a hydrothermal process, in which CTAB inserts into anionic layers and forms covalent bonds with Zn²⁺ ions, then pyrolyzes and removes Zn²⁺ ions during the annealing process, inducing V_Zn formation. H₂-mediated desulfurization generates V_S. The contents of V_Zn and V_S in Zn₃In₂S₆ of 1.9:1.0, 1.1:1.0, 1.0:1.9, and 1.0:3.3 were obtained by adjusting the temperature. V_S&V_Zn-Zn₃In₂S₆ (1.0:1.9) exhibits a fantastic photocatalytic generation rate of 11580.74 µmol g^-1 h^-1 for H₂O₂ which increased 2.4 times compared with V_S-Zn₃In₂S₆, attributing to that dual vacancies promote the local orientated electrical field (LOEF) formation and increase photogenerated-electron transfer from V_S to V_Zn. Electrons delocalize onto adjacent Zn sites, promoting the two-electron oxygen reduction reaction (ORR) pathway. Simultaneously, V_Zn facilitates the migration of h⁺ to the catalyst surface, thereby increasing h⁺ utilization efficiency and accelerating the water oxidation reaction (WOR) process toward H₂O₂ production. V_S&V_Cu-CuIn₂S₄ and V_S&V_Ni-NiIn₂S₄ were successfully synthesized, highlighting its broad applicability as a general approach.