Reverse Charge Transfer Drives d-p Orbital Hybridization in Ruthenium-Oxygen Modified Zn

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.