Janus Cu-Based Alloys with Cooperative Asymmetry for Enhanced C–N Coupling in Electrochemical Urea Synthesis

Electrochemical urea synthesis through C–N coupling is a promising alternative to conventional thermochemical production, yet the activity-determining factors of alloy catalysts under realistic electrochemical conditions remain unclear. Here, we combine density functional theory, solvation-inclusive modeling, and constant-potential analysis to investigate Cu3M alloys for urea synthesis from nitrite and carbon dioxide. The Cu3M stoichiometry preserves a Cu-like adsorption environment while introducing controlled heteroatom-induced asymmetry, and the Cu3M(111) surface provides neighboring fcc and hcp threefold sites for site-resolved analysis. Among the alloys, Cu3Sn(111) exhibits the lowest C–N coupling barrier. We show that intrinsic asymmetry between neighboring triangular adsorption motifs plays a decisive role in governing urea formation, with adjacent fcc sites generally showing more favorable coupling energetics than hcp sites. To quantify this effect, we introduce a Janus descriptor that captures the geometric and electronic asymmetry of neighboring dual sites and correlates strongly with activity across the Cu3M alloy series. Constant-potential calculations further reveal that *CO2 + *NH2 coupling is selectively stabilized at negative potentials through hydrogen bonding. These findings establish an asymmetry-based framework for designing Cu-based alloy catalysts.