Hierarchical Mn ₃ O ₄ /CdZnS Heterojunction with Defined Charge Separation over Redox Sites Enables Efficient CO ₂ Photoreduction

The photocatalytic CO2 reduction process (PCRP) toward valued chemical energy is hindered by random charge separation over redox sites in photocatalysts. Herein, a hierarchical Mn3O4/CdZnS heterojunction is developed by a facile in situ synthesis, enabling defined charge separation over specific redox sites, thereby enhancing CO2-to-CO photoreduction, significantly outperforming pristine counterparts. Specifically, the Cd sites act as electron-rich centers, directly facilitating CO2 reduction. Along with enhanced charge separation, the optimized heterojunction architecture not only strengthens CO2 adsorption but also lowers the energy barrier for the rate-limiting step─*COOH formation─driving CO generation through a two-electron, two-proton mechanism. This direct Z-scheme heterojunction offers experimental and theoretical insights for advancing PCRP via controlling charge separation across redox sites.