Visible-light-driven uranium extraction over an aerogel-like TiO₂/g-C₃N₄/SnS₂ dual Z-scheme photocatalyst

The development of a dual Z-scheme photocatalytic system with stable and strong redox capability is essential for uranium recovery from nuclear wastewater and oceanic environments. Guided by density functional theory (DFT) calculations, an aerogel-like dual Z-scheme TiO₂/graphitic carbon nitride (g-C₃N₄)/SnS₂ (TCS) heterojunction photocatalyst is rationally designed for visible-light-driven uranium extraction. The TCS system achieves an exceptional uranium extraction efficiency of 99.1% within 120 min without the use of any sacrificial agents, which can be attributed to its aerogel architecture that offers a large specific surface area (211.7 m²/g) and abundant accessible active sites. Moreover, the presence of two synergistic Z-scheme electron transfer pathways significantly promotes the separation and migration of photogenerated charge carriers. Notably, the valence bands of both TiO₂ and SnS₂ enable hydroxyl radical (·OH) generation, constructing a double-oxidized dual Z-scheme heterojunction that facilitates enhanced H₂O₂ production and thereby accelerates uranium extraction. Based on these findings, a comprehensive photocatalytic uranium extraction pathway and reaction mechanism are proposed, elucidating the roles of active species and the nature of the final extraction products.