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

Electrocatalytic urea synthesis is a promising alternativeto theenergy-intensive conventional industrial process. However, it lackshighly active and selective catalyst systems. Herein, we report aCu/ZnO stacked tandem gas-diffusion electrode (GDE) for selectiveurea synthesis from electrocatalytic CO2 and nitrate reductionreactions. The ZnO catalyst layer (CL) segment at the inlet providesa high CO concentration to the downstream Cu CL segment, promotingthe conversion of NO3 (-) to *NH2. The CO-mediated NH2 formation accelerates the C-Ncoupling rate for urea synthesis. As a result, the stacked GDE withan optimal ZnO/Cu CL area ratio achieves a high Faradaic efficiencyof 37.4% and a high yield of 3.2 & mu;mol h(-1) cm(-2) for urea at -0.3 V vs RHE under ambient conditions.This work expands the application of tandem electrodes and realizesthe cascade C-N coupling reaction.