Nickel single atom mediated phosphate functionalization of moss derived biochar effectively enhances electrochemical uranium extraction from seawater

Abstract

Electrochemical uranium extraction is considered a promising approach to obtain uranium resources from seawater. Here, we report an electrocatalyst composed of single-atom Ni located at R. japonicum L. biomass derived carbon with phosphate modification (Ni–BC@PO₄) for efficient electrochemical uranium extraction from seawater. By virtue of density functional theory (DFT) calculations, it was confirmed that the synergistic effect of the single-atom Ni and phosphate modification in the R. japonicum L. biomass derived carbon significantly enhances the capture of UO₂²⁺ and accelerates the electron transfer to the captured UO₂²⁺, thereby accelerating the reaction kinetics of uranium electrochemical extraction. As a result, Ni–BC@PO₄ demonstrates excellent uranium extraction capability (2.86 mg g⁻¹ d⁻¹) in real seawater. Relying on various spectroscopic techniques, we further confirm that the captured uranyl ions undergo a continuous and complex reaction process, being captured by phosphate groups, electron reduced, reoxidized by oxidizing radicals, and recrystallized with Na⁺ in solution to generate an Na₂O(UO₃·H₂O)_x precipitate. Furthermore, Ni–BC@PO₄ demonstrates outstanding antibacterial and corrosion resistance. This study provides an example for designing advanced electrocatalysts with highly active centers and strong capturing capabilities for uranium extraction, offering theoretical guidance for seawater uranium resource extraction technology.