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.