Introduction of cation vacancies and iron doping into TiO₂ enabling efficient uranium photoreduction

The reduction of U(VI) to U(IV) in wastewater by semiconductor photocatalysis has become a new highly efficient and low-cost method for U(VI) removal. However, due to the weak absorption of visible light led by wide band gap and low carrier utilization rate resulted from the severe electron-holes recombination, the photoreduction performance of U(VI) is limited. Herein, the Ti vacancies and doped Fe atoms were simultaneously introduced into TiO₂ nanosheet (labeled as 4%Fe-Ti_1-xO₂) as a highly active and stable catalysis for U(VI) photoreduction. Without adding any hole sacrifice agent, 4%Fe-Ti_1-xO₂ nanosheets achieved 99.7% removal efficiency for U(VI) within 120 min. And the 92.1% removal efficiency of U(VI) via 4%Fe-Ti_1-xO₂ nanosheets was still maintained after 5 cycles. Moreover, 4%Fe-Ti_1-xO₂ exhibited dramatic removal rate, 81.6% U(VI) in the solution was removed in 10 min. Further study on the mechanism showed that simultaneously introducing the Ti vacancies and doped Fe atoms in 4%Fe-Ti_1-xO₂ nanosheets improved the visible light utilization and decreased the recombination of photogenerated electron-hole pairs, contributing to the highly efficiency removal of U(VI).