Monitoring Activation Intermediates via Operando Target-Specific NMR Enables Selective C–N Coupling for Urea Electrosynthesis

Electrocatalytic urea synthesis from CO₂ and NO₃^- offers a sustainable nitrogen-carbon route but faces challenges from complex electron transfer and side reactions. Here, we design a SnO₂/CuO_<i>x</i> heterojunction catalyst with an optimized Sn:Cu ratio of 1:5.5, denoted as <i>m</i>-SnO₂/CuO_<i>x</i>, to promote C-N coupling by balancing *CO and *NH₂OH adsorption. The <i>m</i>-SnO₂/CuO_<i>x</i> interface enables selective N-terminal hydrogenation of *NO to *NH₂OH while suppressing the hydrogen evolution reaction and NH₃ formation. In situ infrared spectroscopy reveals the site-specific activation of CO₂ on SnO₂ and NO₃^- on CuO_<i>x</i>. Operando ¹H, ¹³C, ¹⁵N, and ¹⁷O NMR confirms that *NH₂OH couples with *CO via the *H₂NCHO intermediate to form urea. Density functional theory calculations indicate that interfacial charge redistribution lowers energy barriers and stabilizes intermediates. The optimized catalyst delivers a urea yield of 215 mmol g^-1 h^-1 and a Faradaic efficiency of 72.18%. This study underscores the role of rational catalyst design, together with operando insights, in advancing efficient electrocatalytic urea production.