Electrochemical urea synthesis from CO₂ and NO_x⁻ co-electrolysis (EUCN) provides a promising strategy to synthesize urea under ambient conditions. Herein, a homonuclear Cu₂-C₂N diatomic catalyst with Cu₂ dimers on C₂N substrate was developed towards the EUCN. Operando spectroscopic analyses and theoretical simulations reveal that Cu₂ dimers with an optimal axial rotation angle of 45° render the most efficient C–N coupling and hydrogenation, thereby boosting the overall EUCN energetics for urea synthesis. Notably, by integrating plasma-driven air-to-NO_x⁻ conversion, cathodic CO₂ + NO_x⁻ co-electrolysis coupled with anodic glycerol oxidation, the exceptional urea yield rate of 107.2 mmol·h⁻¹·g⁻¹ and Faradaic efficiency of 76.2% were achieved, representing one of the best EUCN performances thus far. The work provides mechanistic EUCN insights into the diatomic catalysts and establishes a sustainable and efficient pathway for urea synthesis.