Modulating *CO Adsorption Behavior: A Mechanistic Strategy for High-Efficiency C-N Coupling in Urea Electrochemical...

Electrochemical urea synthesis through CO₂ and nitrate/nitrite (NO₃ ^-/NO₂ ^-) co-reduction represents a revolutionary alternative pathway for urea formation. Although studies reveal that restraining C-intermediates desorption is beneficial for C-N coupling, *CO adsorption behaviors were usually described by *CO binding energy based on DFT calculations. The intrinsic reason why the *CO adsorption behaviors could modulate the activity for urea formation remains ambiguous. Herein, a series of high-density Cu₁/M₁-NOC electrocatalysts regarding single-atomically dispersed Cu₁/Cu₁, Cu₁/Ni₁, Cu₁/Au₁, or Cu₁/Pd₁ sites anchored on N, O-co-doped carbon were developed for electrochemical urea synthesis. In situ spectroscopy reveals that strengthening *CO binding energy not only enhances *CO coverage but also increases the proportion of linear *CO absorption configuration (*CO_L). The *CO_L with sp hybridization exhibits stronger electrophilicity than that for bridge adsorption, thereby favoring coupling with N-intermediates. Notably, a linear relationship was established by plotting urea yield versus *CO_L coverage. As such, the intrinsic reason for facilitating C─N coupling was originated from the local enrichment of *CO_L. The optimal Cu₁/Pd₁-NOC catalyst exhibits the high urea Faradaic efficiencies of 73.73% and 67.3% with NO₂ ^- and NO₃ ^- as N source, respectively. This research provides an effective strategy to boost urea performance by precisely controlling the *CO adsorption behaviors.