Schottky-Junction-Driven Charge Separation in a 3D rGO/g-C3N4 Aerogel for pH-Tolerant Photocatalytic Uranium Extraction.

Photocatalytic uranium recovery from water bodies is hindered by the poor pH stability and low photocarrier separation efficiency of conventional photocatalysts. Herein, we constructed a recyclable rGO/g-C3N4 aerogel with a Schottky junction that simultaneously addressed both limitations. The optimized rGO/g-C3N4-2 exhibited pH-insensitive performance (pH 2.0-9.0). Furthermore, the Schottky barrier directs unidirectional electron migration toward rGO under illumination, boosting charge separation efficiency to 78.5%. These Schottky-junction-enabled charge dynamics, large specific surface area, the layered structure that facilitated mass and electron transport, and the favorable negative surface charge for UO22+ enrichment collectively contributed to the photocatalytic performance. Consequently, rGO/g-C3N4-2 demonstrated a 92.9% uranium extraction efficiency within 120 min and maintained high efficiency even after 5 cycles under visible light. DFT calculations revealed band gap narrowing to 1.65 eV (vs 2.20 eV for pristine g-C3N4), thereby increasing the light utilization rate. In situ DRIFTS spectroscopy revealed the evolution pathway of active species from •O2- to H2O2. Combined with XPS and XRD analysis, the transformation of U(VI) into (UO2)O2·2H2O after photocatalytic uranium extraction was confirmed. This study presents a pH-tolerant and recyclable photocatalyst with a Schottky junction for uranium extraction from complex aqueous environments, offering a viable strategy for sustainable nuclear fuel cycles.