An all-solid-state S-scheme heterojunction NC/TiO₂@C₃N₄ for efficient uranium recovery from seawater

Photocatalytic uranium extraction from seawater offers a promising approach to address energy scarcity and environmental pollution. However, current photocatalysts face challenges including inefficient light utilization, low selectivity, and poor recyclability. In this study, a novel S-scheme NC/TiO₂@C₃N₄ heterojunction was engineered to enhance photocatalytic uranium extraction from seawater. In this architecture, the one-step thermal annealing generated Ni nanoparticles (Ni-NPs) served as the recombination center for the conduction band electrons of TiO₂ and the valence band holes of g-C₃N₄, enhancing the separation of photogenerated carriers and the overall photocatalytic performance. of photocatalytic capability. Moreover, Ni-NPs also act as a plasmonic enhancer and magnetic carrier, synergistically improving both uranium reduction efficiency (1136.8 mg g⁻¹) and magnetic recyclability (90% capacity retention after 5 cycles). Additionally, the annealed carbon framework provides mesoporous structures enriched with Lewis basic sites (N/O), achieving ultrahigh selectivity (U(VI) concentration reduced to 0.03 mg L⁻¹ in 3 mg L⁻¹ U-spiked natural seawater). This work demonstrates a sustainable strategy for uranium resource recovery and radioactive contamination remediation, highlighting the potential of multi-functional heterojunction design in environmental photocatalysis.