Nano-confinement engineering boosts C–N coupling for urea electrosynthesis

The electrochemical co-reduction of CO₂ and nitrate provides a sustainable route for urea synthesis via C-N coupling, yet kinetic limitations and poor intermediate interactions hinder urea yields. Here, we engineer a nano-confined CuRu bimetallic catalyst within mesoporous carbon hollow spheres (MCHS) to overcome these barriers. By spatially confining reactants and intermediates, the catalyst achieves a urea yield of 12.51 g h^-1 g_cat^-1 at 250 mA cm^-2, with 125-hour stability. In situ spectroscopy and computational analyses reveal that nano-confinement switches the C-N coupling pathway from the thermodynamically favored *COOH-*NH₂ to kinetically driven *OCO-*NO intermediates, bypassing energy barriers. Precise pore-size engineering (4-11 nm) demonstrates that optimal confinement simultaneously enhances reactant transport and intermediate retention, boosting selectivity. This work establishes nano-confinement as a versatile approach for controlling multi-step electrocatalytic processes, enabling sustainable chemical synthesis.