Functionalized Iron–Nitrogen–Carbon Electrocatalyst Provides a Reversible Electron Transfer Platform for Efficient Uranium Extraction from Seawater

Abstract

Uranium extraction from seawater provides an opportunity for sustainable fuel supply to nuclear power plants. Herein, an adsorption-electrocatalysis strategy is demonstrated for efficient uranium extraction from seawater using a functionalized iron-nitrogen-carbon (Fe-N_x -C-R) catalyst, comprising N-doped carbon capsules supporting FeN_x single-atom sites and surface chelating amidoxime groups (R). The amidoxime groups bring hydrophilicity to the adsorbent and offer surface-specific binding sites for UO₂ ²⁺ capture. The site-isolated FeN_x centres reduce adsorbed UO₂ ²⁺ to UO₂ ⁺ . Subsequently, through electrochemical reduction of the FeN_x sites, unstable U(V) ions are reoxidized to U(VI) in the presence of Na⁺ resulting in the generation of solid Na₂ O(UO₃ ·H₂ O)_x , which can easily be collected. Fe-N_x -C-R reduced the uranium concentration in seawater from ≈3.5 ppb to below 0.5 ppb with a calculated capacity of ≈1.2 mg g^-1 within 24 h. To the best of the knowledge, the developed system is the first to use the adsorption of uranyl ions and electrodeposition of solid Na₂ O(UO₃ .H₂ O)_x for the extraction of uranium from seawater. The important discoveries guide technology development for the efficient extraction of uranium from seawater.