3d orbital occupancy regulation stabilizes *CO₂^δ- intermediate for efficient urea electrosynthesis

Electrosynthesis of urea via C-N coupling of CO₂ with nitrate (NO₃^-) has emerged as a fascinating energy-efficient technology. However, the inherent disparity in activation barriers between CO₂ and NO₃^- severely impedes efficient C-N bond formation. Herein, we present an unconventional CO₂-mediated C-N coupling pathway enabled by d-orbital modulation of Cu single atoms anchored on titanium carbide (Cu_SACs/TiC). Combined theoretical calculations and in-situ spectroscopic analyses reveal that strong electronic metal-support interaction (EMSI) downshifts the d band center of Cu_SACs, while spin-charge injection increases Cu [Formula: see text] occupancy from t_2g⁶e_g³ to t_2g⁶e_g⁴. This electronic reconfiguration of Cu_SACs d-orbital enables controlled electron transfer into the CO₂ π* orbitals, facilitating the electron-transfer (ET) to generate *CO₂^δ- intermediate. Simultaneously, the bonding orbitals of *NO₂ generated on the TiC directly couple with the antibonding orbital of *CO₂^δ-, promoting C-N bond formation toward urea. Consequently, the optimal Cu_SACs/TiC delivers an outstanding C selectivity of 97.8%, along with an excellent Faradaic efficiency (FE) of 50.1% and yield of 558.8 μg h^-1 mg_cat^-1 for urea production in the electrolyte of 0.05 mol L^-1 KNO₃ and 0.1 mol L^-1 KHCO₃. This work highlights a unique C-N coupling pathway via d-orbital engineering for efficient electrochemical C-N bond formation from CO₂ and nitrogenous feedstocks.