The electrochemical synthesis of urea on triatomic cluster/Cu catalysts: A theoretical study

Abstract

Urea (NH₂CONH₂), a crucial nitrogen fertilizer and industrial raw material, is typically synthesized under rigorous reaction conditions. Currently, the electrocatalytic transformation of N₂ and CO₂ into urea is a promising strategy. However, finding a high-selectivity and high-activity catalyst remains a significant challenge. Herein, the activity of a series of transition metal clusters (VIII and IB groups) on copper-based catalysts for electrochemical coupling of CO₂ and N₂ has been systematically studied to produce urea via density functional theory (DFT). Most catalysts exhibit good thermodynamic stability and accomplish co-adsorb CO₂ and N₂. Notably, Fe3 and Ni3/Cu100 catalysts achieve C-N coupling via *CO and *N₂, whereas Ru3, Rh3, Os3, and Ir3/Cu100 catalysts accomplish C-N coupling via *CO and *NHNH. Among all catalysts, the Ni3/Cu100 catalyst features excellent catalytic activity with a rate-determining step as low as 0.480 eV, and its C-N coupling only needs to overcome a barrier of 0.844 eV. Additionally, the Ni3/Cu100 catalyst can effectively inhibit the hydrogen evolution reaction (HER), further protonation of *CO and ammonia formation, thereby ensuring high selectivity for urea. Electronic structures analysis further reveals an “acceptance-donation” mechanism for the activation of *CO₂ and *N₂, with the introduction of the Ni3 cluster showing a decisive role. Therefore, this study may establish the foundation for the electrochemical synthesis of urea.