Kinetically matched C–N coupling toward efficient urea electrosynthesis enabled on copper single-atom alloy

Abstract

Chemical C–N coupling from CO2 and NO3–, driven by renewable electricity, toward urea synthesis is an appealing alternative for Bosch–Meiser urea production. However, the unmatched kinetics in CO2 and NO3– reduction reactions and the complexity of C- and N-species involved in the co-reduction render the challenge of C–N coupling, leading to the low urea yield rate and Faradaic efficiency. Here, we report a single-atom copper-alloyed Pd catalyst (Pd4Cu1) that can achieve highly efficient C–N coupling toward urea electrosynthesis. The reduction kinetics of CO2 and NO3– is regulated and matched by steering Cu doping level and Pd4Cu1/FeNi(OH)2 interface. Charge-polarized Pdδ–-Cuδ+ dual-sites stabilize the key *CO and *NH2 intermediates to promote C–N coupling. The synthesized Pd4Cu1-FeNi(OH)2 composite catalyst achieves a urea yield rate of 436.9 mmol gcat.–1 h–1 and Faradaic efficiency of 66.4%, as well as a long cycling stability of 1000 h. In-situ spectroscopic results and theoretical calculation reveal that atomically dispersed Cu in Pd lattice promotes the deep reduction of NO3– to *NH2, and the Pd-Cu dual-sites lower the energy barrier of the pivotal C–N coupling between *NH2 and *CO.