Hydroxycarbonate-Induced Asymmetric Bridging-Adsorption of CO<sub>2</sub> to Trigger C–N Coupling for Urea Electrosynthesis
Qianqian Song, Yingbin Zhang, Ziyang Wu, Min Kuang, Jun Chen, Jianping Yang
Abstract
The electrocatalytic urea synthesis has emerged as a promising alternative strategy to replace the current energy-intensive industrial Haber–Bosch processes which are limited by sluggish C–N coupling and low selectivity because of the unmatched reduction kinetics of CO 2 and nitrogen-based precursors. Herein, a thermodynamically spontaneous early stage C–N coupling pathway of *CO 2 + *NO → *NOCO 2 is established through the asymmetric bridging-adsorption of CO 2 enabled by hydroxycarbonate-induced CO 3 2– -Cu 2+ dual sites on the tandem electrocatalyst of copper carbonate hydroxide and iron oxide grown on carbon fibers (CuCH/α-Fe 2 O 3 –CFs). This asymmetric adsorption induces a pronounced electron-deficient state of carbon atoms in CO 2 due to bidirectional electron transfer toward both the CO 3 2– and the Cu 2+ centers. Coupled with the directional migration of *NO intermediates at the interface, effectively suppress the subsequent protonation of *CO 2 while promoting nucleophilic attack by *NO, thereby driving spontaneous initial C–N coupling of *CO 2 and *NO and significantly lowering the energy barrier of the C–N coupling step. The results demonstrate a urea Faradaic efficiency of 78.7% and urea yield rate of 1794.6 μg h –1 mg cat –1 at an ultralow applied potential of −0.20 V vs RHE, surpassing most reported catalysts to date.