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 Pd^δ--Cu^δ+ 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 g_cat.^-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.