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

Electrocatalytic urea synthesis from CO 2 and NO 3 – offers a sustainable nitrogen–carbon route but faces challenges from complex electron transfer and side reactions. Here, we design a SnO 2 /CuO x heterojunction catalyst with an optimized Sn:Cu ratio of 1:5.5, denoted as m -SnO 2 /CuO x, to promote C–N coupling by balancing *CO and *NH 2 OH adsorption. The m -SnO 2 /CuO x interface enables selective N-terminal hydrogenation of *NO to *NH 2 OH while suppressing the hydrogen evolution reaction and NH 3 formation. In situ infrared spectroscopy reveals the site-specific activation of CO 2 on SnO 2 and NO 3 – on CuO x . Operando 1 H, 13 C, 15 N, and 17 O NMR confirms that *NH 2 OH couples with *CO via the *H 2 NCHO 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.