Single-atom cu sites with engineered oxygen vacancies boost electrocatalytic urea production from CO₂ and nitrate

This study develops a Cu single-atom catalyst anchored on oxygen vacancy-engineered CeO₂ (Cu-CeO₂-Vo) for efficient electrocatalytic urea synthesis via co-reduction of NO₃^- and CO₂. Synthesized through wet impregnation and controlled calcination, Cu-CeO₂-Vo features atomically dispersed Cu sites and abundant oxygen vacancies (OVs), as validated by XRD, TEM, XPS, XAFS, and Raman spectroscopy. At -1.55 V vs. RHE, the catalyst achieves a urea production rate of 59.96 mmol h^-1 g_cat^-1 with 7.75 % Faradaic efficiency, surpassing most reported electrocatalysts. In situ FTIR and Raman spectroscopy reveal that OVs promote CN coupling by stabilizing *NO intermediates, enhancing *CO adsorption, and facilitating the formation of a key *OCNO species. Density functional theory (DFT) calculations confirm that OVs reduce energy barriers for critical steps, including *OCNO generation and hydroxyl desorption. This work elucidates the mechanistic role of OVs in urea synthesis and provides design principles for advanced CN coupling electrocatalysts.