Lattice Oxygen-Driven Co-Adsorption of Carbon Dioxide and Nitrate on Copper: A Pathway to Efficient Urea Electrosynthesis

The electrochemical coupling of CO2 and NO3– on copper-based catalysts presents a sustainable strategy for urea production while simultaneously addressing wastewater denitrification. However, the inefficient random adsorption of CO2 and NO3– on the copper surface limits the interaction of the key carbon and nitrogen intermediates, thereby impeding efficient C–N coupling. In this study, we demonstrate that the residual lattice oxygen in oxide-derived copper nanosheets (OL-Cu) can effectively tune the electron distribution, thus activating neighboring copper atoms and generating electron-deficient copper (Cuδ+) sites. These Cuδ+ sites enhance CO2 adsorption and stabilize *CO intermediates, which enables the directional NO3– adsorption at adjacent Cuδ+ sites. This mechanism shortens the C–N coupling pathway and achieves a urea yield of up to 298.67 mmol h–1 g–1 at −0.7 V versus RHE, with an average Faradaic efficiency of 31.71% at a high current density of ∼95 mA cm–2. In situ spectroscopic measurements confirmed the formation of Cuδ+ sites and tracked the evolution of the key intermediates (i.e., *CO, *NO, *OCNO, and *NOCONO) during urea synthesis. Density functional theory calculations revealed that Cuδ+ sites promote adjacent coadsorption of *CO and *NO3, as well as *OCNO and *NO3, significantly improving C–N coupling kinetics. This study underscores the critical role of lattice oxygen in facilitating adjacent coadsorption and improving C–N coupling selectivity.