Elucidating Relay Catalysis on Copper Clusters With Satellite Single Atoms for Enhanced Urea Electrosynthesis

Relay catalysis represents significant efficacy in alleviating competition among different reactants during coupling reactions. However, a comprehensive understanding of the reaction mechanism underlying relay catalysis for the urea electrosynthesis remains challenging. Herein, we have developed a catalyst (Cu_AC-Cu_SA@NC) comprising Cu atomic clusters (Cu_AC) with satellite Cu─N₄ single atoms (Cu_SA) sites on the nitrogen-doped porous interconnected carbon skeleton (NC), enabling elucidation of a relay catalysis process for co-reduction of CO₂ and NO₃ ^-. The designed Cu_AC-Cu_SA@NC catalyst exhibits an approximately threefold higher urea yield rate compared to that of Cu_SA@NC at -1.3 V versus RHE. Ex-situ experimental results and in-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy analysis reveal a formation sequence between the *NH₂ and *NH₂CO species on Cu_AC-Cu_SA@NC with increasing reduction potential. The combination of theoretical calculations further elucidates that the relay catalysis pathway involves "Cu_AC" sites facilitating the conversion of *NO₃ to *NO_x, followed by a hydrogenation process to form *NH₂ with *H from water dissociation promoted by "Cu_SA" sites, which subsequently couples with *CO₂ to produce urea. This work provides novel insights into the investigation of coupling reactions, but not limit to, urea synthesis.