Rapid Electrochemical Uranium Extraction from Real Seawater via the Intermediate of Vacancy-Trapped Isolated Uranyl

Electrochemical uranium extraction from seawater is a vital project for the sustainable development of the nuclear industry, which requires selective intrinsic binding sites for uranyl. In this work, oxygen vacancies (O vacancies) were developed as an atomically identified confinement for uranyl, and thus, rapid uranium extraction from seawater was achieved. In a short period of 700 s, In₂O₃ nanosheets with rich O vacancies (V_o-rich In₂O_3-x nanosheets) exhibited a high extraction efficiency of 88.3% in simulated seawater with 75 μg/L of uranium, with a facile desorption process of adding a reverse potential. In 3 L of real seawater, the V_o-rich In₂O_3-x exhibited an extraction efficiency of 52.6% when applying 10 cycles of electrochemical extraction-desorption, representing an extraction rate of ∼3.5 mg/g per day considering the operation time between each cycle. The mechanistic study revealed that the oxygen atom in the uranyl tended to insert the oxygen vacancy and form the intermediate of isolated uranyl. Such "quasi single atom" intermediate facilitated both the initial uranium adsorption and the following uranium deposition.