Cationic Vacancy Engineering Enables Cu/Ti1− x O2 Schottky Heterojunctions for Boosted U(VI) Photoreduction

Abstract Photocatalysis is capable of reducing soluble U(VI) to insoluble U(IV). Nevertheless, photogenerated carrier recombination restricts reaction kinetics, and additional sacrificial agents are generally required to sustain efficient U(VI) photoreduction. Herein, we report a synergistic strategy integrating cationic Ti vacancies and Schottky junctions to fabricate Cu/Ti1−xO2 photocatalysts toward efficient U(VI) photoreduction. Advanced spectroscopic characterizations reveal that the localized surface plasmon resonance (LSPR) effect of Cu nanoparticles significantly broadens the light absorption range of Cu/Ti1−xO2. Furthermore, PL spectra and electrochemical characterizations verify that the synergy between Ti vacancy defects and Schottky junctions accelerates interfacial electron migration and suppresses the recombination of photogenerated charge carriers in the Cu/Ti1−xO2 system, drastically boosting its photocatalytic activity. DFT calculations further verify that Ti vacancies strengthen the strong interaction between Cu nanoparticles and Ti1−xO2, and induce prominent electron spin polarization near the Fermi level to greatly facilitate the separation of photogenerated charge carriers. Benefiting from the above merits, the optimized 5Cu/Ti1−xO2 delivers a maximum U(VI) removal efficiency of 98.48% without the addition of any sacrificial agents. More importantly, the catalyst retains outstanding U(VI) elimination capacity under interference from coexisting anions and cations. Meanwhile, seven consecutive cycling tests demonstrate its robust reusability. This study offers an innovative strategy for photocatalyst construction by coupling cationic vacancies with metal active sites.