Dual-Channel Reactions on TiO₂@PCN S-Scheme Heterojunction Enable the Photocatalytic Seawater Uranium Extraction...

Photocatalysis offers a promising method for uranium extraction from seawater. However, the conventional photocatalytic reduction pathway faces challenges due to the adverse effects of oxygen and carbonate under ambient conditions. In this study, an S-scheme heterojunction is constructed by loading TiO₂ onto tubular graphitic carbon nitride (PCN) for the photocatalytic U(VI) extraction. The photogenerated electrons from the conduction band of TiO₂ transfer to the valence band of PCN, enhancing both the oxidation and reduction capabilities of the catalytic system. This process induces significant H₂O₂ generation via both reduction and oxidation reactions. The produced H₂O₂ further complexes with uranyl ions to form studtite precipitates, thereby achieving efficient uranium separation. The system achieves a U(VI) separation efficiency of 95.8% within 210 min of illumination. Unlike traditional photocatalytic reduction of U(VI), this reaction is unaffected by air atmosphere or carbonate, enabling 100% uranium extraction from 4 L of natural seawater under sunlight.