Amplified Single-Atom U–O Interfacial Effect Originated from U 5f-O 2p Hybridization over UOx/GO for Enhanced Nitrogen Reduction Reaction

Uranium-based catalysts have been regarded as promising candidates for N₂ fixation owing to the low-valent uranium metal active sites possessing the ability to enhance the electron back-donating to the π* antibonding orbitals of N₂ for N≡N dissociation. Herein, we report a directional half-wave rectified alternating current electrochemical method to confine oxygen-rich uranium precursors over ultrathin 2D GO nanosheets. The as-prepared uranium catalysts exhibit a considerable Faradaic efficiency of 12.7% for NH₃ and the NH₃ yield rate of 18.7 μg h^-1 mg^-1 for N₂ electroreduction. Operando XAS and isotope-labeling FTIR further unravel the preferred nitrogen adsorption reaction intermediate N-(2O_ax-1 U-4O_eq) and confirm the key *N₂H_y intermediate species derived from the fed N₂ gas. Theoretical simulations demonstrate that the U-O atomic interface originated from U 5f-O 2p orbital hybridization can accumulate partial charge from GO, which can facilitate the N≡N dissociation and lower the thermodynamic energy barrier of the first hydrogenation step.