Oxygen vacancy-induced spin polarization of tungsten oxide nanowires for efficient photocatalytic reduction and immobilization of uranium(VI) under simulated solar light

Tungsten oxide nanowires (WO3_x) with rich oxygen vacancies (OVs) were fabricated through a facile hydro-thermal method, which had both high adsorptive capability and photocatalytic activity. 95.1% of total U(VI) (C0 = 10 mg/L) was removed by WO3_ x at pH 5, and 79.9% was transformed to U(IV) to achieve reductive immobilization after photocatalysis under simulated solar light. Band structure and optical characterizations indicated WO3_x had narrower band gap energy, but higher charger carrier separation and transfer rates compared with conventional WO3. Density functional theory (DFT) calculations further demonstrate the spin polarization state electrons of W 5d in WO3_x due to the construction of OVs, thus greatly inhibiting recombi-nation of electron-hole pairs. In addition, the electron density increases in WO3_x and the photogenerated e- in the conduction band of WO3_x has higher reduction ability than WO3, leading to more efficient electron transfer from WO3_x to UO22+ after photo-excitation for U(VI) reduction.