Engineering nonstoichiometric Zn1 + mIn2S4+m photocatalysts with enhanced internal electric fields for efficient H2O2 generation: mechanistic insights

Nonstoichiometric Zn 1+m In₂S 4+m samples were synthesized by raising Zn and S precursor ratios, enhancing [001] asymmetry. • Enhanced asymmetry gives Zn 1+m In₂S 4+m a stronger intrinsic internal electric field (IEF), boosting charge separation. • Zn₂In₂S₅ shows a H₂O₂ production rate of 2452 μmol g⁻¹ h⁻¹ in air, 3.09 times that of ZnIn₂S₄. • This work demonstrates the feasibility of enhancing the internal electric field via compositional regulation. Two-dimensional ZnIn 2 S 4 is regarded as a promising candidate for photocatalytic H 2 O 2 production owing to its unique crystal structure. However, its practical photocatalytic efficiency remains limited by the severe recombination of photogenerated charge carriers and sluggish charge carrier migration. The intrinsic asymmetric crystal structure of ZnIn 2 S 4 generates an internal electric field (IEF), which effectively suppresses charge carrier recombination and promotes charge carrier separation and migration. In this work, the structural asymmetry of Zn 1+m In 2 S 4+m was systematically enhanced by simultaneously increasing the Zn and S source ratios in the precursors, thereby significantly strengthening the IEF. Benefiting from the enhanced IEF, the optimized Zn 2 In 2 S 5 sample exhibits an outstanding H 2 O 2 production rate of 2452 μmol g⁻¹ h⁻¹ , approximately 3.09 times that of ZnIn 2 S 4 . This work not only demonstrates the feasibility of strengthening the IEF through composition regulation to enhance photocatalytic performance, but also provides new insights into the design of highly efficient photocatalysts.