Efficient charge separation in sulfur doped AgFeO photocatalyst for enhanced photocatalytic U(VI) reduction: The role of doping and mechanism insights.

Photocatalytic reduction of U(VI) in aqueous solutions has been considered as an efficient and promising technology to solve radioactive U pollution. In this work, density functional theory (DFT) calculations were firstly employed to optimize and compare the adsorption configurations combined uranium with four given photocatalysts, then their adsorption energies were - 0.97 eV for AgFeO, - 1.15 eV for Zn doped AgFeO, - 1.73 eV for Cu doped AgFeO and - 2.66 eV for S doped AgFeO, respectively, indicating the sulfur doping plays a major role in U(VI) photoreduction. Herein, a visible light responsive efficient sulfur doped AgFeO photocatalyst (S doped AgFeO) was synthesized and utilized to photocatalytic reduction of U(VI) in aqueous solutions. According to XRD, XPS and TEM analysis, the sulfur was successfully doped in AgFeO via the hydrothermal method. The batch experimental showed that S doping enhanced the U(VI) photoreduction activity of AgFeO, and the S-AFO-3 photocatalyst exhibited the highest photocatalytic activity (92.57%), which was 1.5 times than that of pure AgFeO. ESR, PL and DFT results demonstrated that the enhancement of adsorbed U(VI) photoreduction was attributed to the own unique effect of oxygen vacancy defects and efficient charge separation of S doped AgFeO photocatalyst. Due to its higher adsorption energies, fast-U(VI) photoreduction rate and superior chemical stability, the sulfur doped AgFeO photocatalyst is hoped for water remediation containing U(VI) wastewater.