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

Abstract

Uranium-based catalysts have been regarded as promising candidates for N 2 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 N 2 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 NH 3 and the NH 3 yield rate of 18.7 μg h –1 mg –1 for N 2 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 *N 2 H y intermediate species derived from the fed N 2 gas. Theoretical simulations demonstrate that the U–O atomic interface originated from U 5 f -O 2 p 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.