Performance and Mechanism of MoS2/Octahedral Fe3O4 Composite Interface Catalytic Electrochemical Seawater Extraction of Uranium

Abstract

Extracting uranium from seawater is an effective strategy for sustainable nuclear fuel supplementation. Uranium in seawater mainly exists in the form of hexavalent uranyl(U(Ⅵ)), although the total amount is large, the mass fraction of U(Ⅵ) is only 3.3×10−9, and many metal ions coexist with uranium. Extracting uranium from seawater is extremely challenging. Electrochemical seawater uranium extraction has become an emerging method for seawater uranium extraction due to its advantages over physical and chemical adsorption processes, such as fast reaction rate, strong anti-interference ability, and simple desorption. However, due to the lack of research on the structure-activity relationship between catalysts and uranium extraction performance, the rational design of highly active electrocatalysts remains a challenge. In this work, we proposed an interface bonding strategy by using a simple hydrothermal method to bond the {2 2 2} fact of octahedral Fe3O4 to the {0 0 2} fact of MoS2. This significantly improves the electron transfer rate at the interface and the cycling stability of Fe3O4, verifying the feasibility of interface bonding for the electrochemical extraction of uranium from seawater. After 7 hours of electrochemical extraction in a simulated solution, the extraction efficiency of uranium can reach 96%. Meanwhile, the experimental results of coexisting ion extraction of uranium indicated that MoS2/Fe3O4 has good selectivity for uranium and anti-interference ability against coexisting ions. Electrochemical extraction is also performed in 10 L natural seawater with a yield of 27.2 μg. The extraction amount of uranium is 5.44 mg/g. A series of characterizations such as XPS and HRTEM, show that Fe3O4 is dispersed on the surface of MoS2 and effectively bound through interfacial interactions. This dispersion effectively solves the aggregation problem of Fe3O4, and the stability of MoS2 structure ensures the cycling stability of Fe3O4. By combining the MoS2 and Fe3O4 at the interface, an efficient electron transfer channel can be constructed, accelerating electron transfer and achieving the goal of simultaneously improving the selectivity, stability, and electron transfer rate of the catalyst. Therefore, the interfacial regulation strategy proposed in this work utilizes the synergistic effects of different components in the composite material to achieve stability and the cyclicity of the catalyst in seawater uranium extraction. At the same time, the interface control strategy will also provide a feasible solution for achieving efficient reduction and extraction of uranyl in a series of complex environments such as seawater. And the electron transfer path and the species change of uranium during catalytic reduction need to be further explored in the mechanism analysis in this work.

Keywords

• electrochemistry
• uranium extraction from seawater
• interface