In situ construction of MnIn2S4/Ti3C2TxMXene Schottky junction composites for efficient photoreduction and recovery of U(VI)

Photocatalytic reduction of soluble U(VI) to less soluble U(IV) is a plausible method to remove the radioactive pollution while recovery uranium resource. Herein, MXene (Ti3C2Tx) nanosheets serve as a substrate for in-situ anchoring of MnIn2S4 nanosheets to form MnIn2S4/Ti3C2Tx Schottky junction for efficient photocatalytic reduction U(VI) without sacrificial agent added under visible irradiation. The optimized MnIn2S4/Ti3C2Tx presents 97.6% photoreduction efficiency toward U(VI) in 60 min, which is 33% higher than that of MnIn2S4 (64.6%), and the extraction capacity reached 1.83 g/g after 300 min reaction. Besides, the optimized MnIn2S4/Ti3C2Tx still achieves 98.7% U(VI) photoreduction efficiency in U(VI)-contained actual seawater under visible irradiation and shows efficient reduction (84.2%) for U(VI) under actual natural light. Theoretical calculation and experiment results show that the Schottky junction between Ti3C2Tx and MnIn2S4 results in the electron-donation effect of the MnIn2S4 nanosheets, which inhibits the backflow of photoinduced electrons and the ·O2– species are contributing to the U(VI) photoreduction process. The work presents a novel insight for U(VI) photoreduction and recovery over the Schottky heterostructure.