Dirección de Intermediarios en la Producción Fotocatalítica de H2O2 para Potenciar la Extracción de Uranio del Agua...

Extracting uranium from seawater is crucial for ensuring the supply of uranium resources and the sustainable development of nuclear energy. Photocatalysis-assisted extraction strategy, where photo-catalytically generated H₂O₂ reacts with uranyl ions to form metastudtite, could effectively enhance the extraction capacity and kinetics, while the mechanisms remain unclear, especially in seawater. Herein, the relationship between photocatalytic H₂O₂ production mechanisms and subsequent uranium removal was investigated by using oxidized red phosphorus-doped carbon nitride (ORP-CN) and MOF-functionalized carbon nitride (MOF-CN). Both catalysts exhibited similar H₂O₂ production rates, while ORP-CN demonstrated a 13 times higher uranium extraction efficiency. We revealed that ORP-CN follows an indirect two-step 2e^- oxygen reduction reaction (ORR) pathway, producing ·OOH radical as intermediates. Whereas MOF-CN mainly followed a direct one-step 2e^- ORR process. DFT simulations demonstrated that ·OOH radical can coordinate with uranyl carbonate more efficiently than H₂O₂ at seawater interfaces, leading to rapid metastudtite formation. This mechanistic advantage endowed ORP-CN with exceptional uranium recovery property, achieving an extraction capacity of 6.73 mg/g/day in natural seawater without sacrificial agents. Our findings directly link H₂O₂ generation pathways to uranium extraction efficiency, highlighting reactive oxygen intermediates as critical drivers in seawater uranium recovery and providing a theoretical basis for designing advanced photocatalysts.