Spatial Management of CO Diffusion on Tandem Electrode Promotes NH2 Intermediate Formation for Efficient Urea Electrosynthesis

Electrocatalytic urea synthesis is a promising alternative to the energy-intensive conventional industrial process. However, it lacks highly active and selective catalyst systems. Herein, we report a Cu/ZnO stacked tandem gas-diffusion electrode (GDE) for selective urea synthesis from electrocatalytic CO2 and nitrate reduction reactions. The ZnO catalyst layer (CL) segment at the inlet provides a high CO concentration to the downstream Cu CL segment, promoting the conversion of NO3– to *NH2. The CO-mediated NH2 formation accelerates the C–N coupling rate for urea synthesis. As a result, the stacked GDE with an optimal ZnO/Cu CL area ratio achieves a high Faradaic efficiency of 37.4% and a high yield of 3.2 μmol h–1 cm–2 for urea at −0.3 V vs RHE under ambient conditions. This work expands the application of tandem electrodes and realizes the cascade C–N coupling reaction.