Oxygen-Vacancy Confined Uranium Single-Atom Over Titanium Dioxide Nanosheets for Efficient Nitrogen Fixation

Uranium-based catalysts have been regarded as promising candidates for N2 fixation owing to its unique 5f orbital with flexible oxidation states. Herein, for the first time, we report uranium (U) single atoms dispersed on TiO2 nanosheets via oxygen vacancies confinement, for N2 electroreduction. The single-atom U catalyst exhibits a high NH3 yield rate of 40.57 μg h-1 mg-1 with a considerable Faradaic efficiency of 25.77%, ranking top among the reported nitrogen-free catalysts. Isotope-labeling operando synchrotron radiation infrared spectroscopy verify the key *N2Hy intermediate species derived from the fed N2 gas. By using operando X-ray absorption spectroscopy, we identify the enhanced metal-support interaction between U single atoms and TiO2 lattice with more U-Olatt coordination under working conditions. Theoretical simulations demonstrate that the evolved 1Oads-U-4Olatt moieties act as key electron back-donation centers to lower the thermodynamic energy barrier for N2 dissociation and first hydrogenation step. This work provides the possibility of tailoring the interaction between metal active sites and support for designing high-performance actinide-based single-atom catalysts.