Actinide-uranium single-atom catalysis for electrochemical nitrogen fixation

Actinide-based catalysts have been regarded as promising candidates for N₂ fixation owing to their unique 5f orbital with flexible oxidation states. Herein, we report for the first time the dispersion of uranium (U) single atoms on TiO₂ nanosheets via oxygen vacancy confinement for N₂ electroreduction. The single-atom U catalyst exhibited a high NH₃ yield of 40.57 μg h^-1 mg^-1, with a reasonably high Faraday efficiency of 25.77%, ranking first among the reported nitrogen-free catalysts. Isotope-labeling operando synchrotron infrared spectroscopy verifies that the key *N₂H_y intermediate species was derived from the N₂ gas of the feed. By using operando X-ray absorption spectroscopy, we found enhanced metal-support interaction between U single atoms and TiO₂ lattice with more U-O_latt coordination under working conditions. Theoretical simulations suggest that the evolved 1O_ads-U-4O_latt moieties act as a critical electron-feedback center, lowering the thermodynamic energy barrier for the N₂ dissociation and the first hydrogenation step. This work provides the possibility of tailoring the interaction between metal active sites and supports for designing high-performance actinide-based single-atom catalysts.