Redirecting Charge Distribution and Spatial Proximity of Co-O-Cu Motif with 4f-2p-3d Orbital Hybridization for High-Efficiency Urea Electrosynthesis.

Abstract

Electrocatalytic CO₂/NO₃ ^- co-reduction to access urea typically relies on the tailored two-site catalysts, with the complexity of C/N-intermediate generation and C─N coupling that limit urea synthesis efficiency. Here, a 4f (Ce)-2p (O)-3d (Co) orbital hybridization maneuver is demonstrated to customize a spin-polarized Co-site and a relatively electron-rich Cu-site for generating *NH₂ and *CO species to undergo C─N coupling to access urea, respectively, delivering a production rate of 2612.4 µg mg^-1 h^-1 at -0.27 V_RHE, with an ultrahigh Faradaic efficiency (85.7%). Mechanistic investigations elucidate that the 4f-2p-3d motif enables the high-spin Co²⁺ (t_2g ⁵e_g ²) translation toward low-spin Co³⁺ (t_2g ⁶e_g ⁰), which enhances the electronic interaction between the e_g-orbital of Co and 𝜎-orbital of *NO, favoring *NH₂ formation. Further, the electron-deficient Co³⁺-site formed can act as a localized electron acceptor to manipulate the electron structure of the adjacent Cu-site, strengthening the hybridization degree between the catalyst's Cu 3d and C 2p of CO₂ to foster *CO generation. Then, interposed Ce narrows the Co─O─Cu distance, which spatially benefits *NH₂ and *CO coupling to form the C─N bond, overall promoting urea synthesis. The synergy of electronic interaction and geometric effect offers a feasible paradigm to precisely customize activity centers for high-efficiency waste feedstock valorization.