Harmonizing the energy band between adsorbent and semiconductor enables efficient uranium extraction

Herein, we harmonized the energy band of defective molybdenum disulfide (MoSx) and reduced graphene oxide (RGO) through manipulating the concentration of S vacancies for efficient U(VI) reduction. The analysis of band structure revealed that the EF and conduction band of MoSx downward shifted with the increase of S vacancies, which lowered the schottky barrier but simultaneous decreased the reducibility of photogenerated electrons. Accordingly, the removal rate of U(VI) under the irradiation of simulated sunlight exhibited a volcanic relationship with the concentration of S vacancies in MoSx/RGO. Specifically, the maximum removal rate reached 91.6% with nearly 83.4% of tetrahydrated uranium (U(IV)) species over MoSx/RGO heterojunction. In addition, the extraction efficiency of MoSx/RGO heterojunction kept steady in 5-cycle test and exhibited less than 4.5% decrease in the presence of non-redox-active competing metal cations.