Dynamic reversible evolution of vicinal/bonding heteronuclear diatoms drives relay reductive C–N coupling for enhancive urea electrosynthesis

The precise construction of dual active sites has been uncovered for the electroreduction of C- and N-based precursors to synthesize urea. However, these strategies often face adsorption scaling constraints and spatial restrictions that hinder C–N coupling, resulting in suboptimal activity and selectivity. Here, we showcase a dynamically reversible evolution between vicinal Fe/Cu diatoms and alloy-like Fe–Cu sites, enabling cascade protonation and efficient C–N coupling. This approach markedly enhances urea electrosynthesis from CO₂ and NO₃⁻, achieving an ultrahigh urea yield of 2421.2 μg h⁻¹ mg⁻¹, Faraday efficiency (FE) of 70.4%, and C-selectivity of 96.7%, surpassing state-of-the-art dual-site electrocatalysts. Operando spectroscopy and theoretical calculations reveal that neighboring Fe/Cu diatoms facilitate the selective adsorption and hydrogenation of NO₃⁻ and CO₂ into the key intermediates (*NO and *CO). Furthermore, alloy-like Fe–Cu sites, formed in situ due to declined metal surface free energy driven by electron transfer, facilitate C–N coupling and subsequent protonation to selectively produce urea, while dynamically reverting to vicinal Fe/Cu diatoms. This work provides new insights into the relay catalytic strategy for urea electrosynthesis by modulating the dynamic atomic-scale evolution of active sites. (Figure presented.).