Reverse Charge Transfer Drives d-p Orbital Hybridization in Ruthenium-Oxygen Modified Zn₃In₂S₆ for Hydrogen Peroxide...

Artificial photosynthesis is emerging as a promising approach for sustainable H₂O₂ production. However, controlling the electronic structure and charge carrier dynamics to enhance oxygen adsorption and activation remains a major challenge. Here, ruthenium and oxygen co-modified Zn₃In₂S₆ (O-Ru-ZIS) is presented, a catalyst design to achieve reverse photogenerated carrier transfer through tailored electronic modulation. The introduction of oxygen atoms, with higher electronegativity than sulfur, induces significant surface charge redistribution and transforms the Ru─S coordination environment from Ru─S₄ (in Ru-ZIS) to Ru-S₁O₃ (in O-Ru-ZIS), as revealed by synchrotron radiation X-ray absorption spectroscopy (SR-XAS). This structural transition drives a reversal in charge carrier transfer pathways: in Ru-ZIS, photogenerated electrons transfer from Ru sites to In sites, whereas in O-Ru-ZIS, electrons transfer from In sites to Ru sites, as validated by in situ XPS and fs-TA spectra. This reverse charge transfer enhances d-p orbital hybridization between Ru and O₂, facilitating efficient charge redistribution, strong oxygen adsorption, and activation. In situ spectroscopic studies and density functional theory (DFT) calculations further corroborate these mechanistic insights. As a result, the O-Ru-ZIS catalyst exhibits a photocatalytic H₂O₂ evolution rate of 3659 µmol g^-1 h^-1 under ambient conditions without requiring sacrificial agents, significantly outperforming conventional Zn₃In₂S₆-based systems and other reported photocatalysts for H₂O₂ photosynthesis.