Capturing aqueous uranyl ions into catalytic nanometric shells of liquid metal droplets for electrochemical reduction

Extraction of aqueous uranium element for practical applications has drawn growing attention due to its significance for both green energy acquirement and ecological environment remediation. Herein, the liquid metal droplets produced by a facile ultra-sonication process are found to be able to capture aqueous uranyl ions with a maximal adsorption capacity up to 237 mg g−1 (1483 mg cm−3), and further to reduce them into insoluble UO2 nanoparticles (2–5 nm in diameter). With the homogeneous immobilization of UO2 nanoparticles, the ultra-thin shell of liquid metal droplets exhibits a high catalytic activity towards electrochemical reductions e.g., CO2 reduction. The liquid metal core, when supporting on the electrodes, also offers the efficient electro-transporting pathway for electrochemical reaction. With a high formate selectivity, a faradaic efficiency ≥91.4 % and a generation rate as high as 988.9 mmol g−1h−1 of C1 products (i.e., CO and formate) are achieved in the CO2 reduction. Thus, this study may offer not only a unique platform of liquid metal nanodroplets for extracting uranium from water, but also a novel route of fabricating high-efficiency electrochemical catalysts for CO2 conversion.