Identification and Optimization of Spinel Oxide Geometric Configurations for Enhanced C−N Coupling Reaction

Abstract Electrocatalytic co‐reduction of nitrate (NO 3 − ) and carbon dioxide (CO 2 ) for urea synthesis offers an eco‐friendly solution to mitigate nitrate contamination and reduce the energy demands. The investigation of the catalyst geometric and electronic structures is critical to elucidating the reaction mechanisms for the design of high‐performance catalysts. Herein, this work systematically studied the cobalt (Co) atom geometric configurations in Co‐based spinel oxides for C−N coupling reaction. It demonstrated that C−N coupling is more likely to take place at octahedral Co (Co Oh ) sites instead of tetrahedral Co (Co Td ) sites and the Co Oh sites in spinel structures facilitating both electron and ion transport. Leveraging the synergistic effect between Co Oh and Co Td sites, Co 3 O 4 achieved the highest Faradaic efficiency and urea yield. Meanwhile, isotope labeling experiment confirmed the urea formation through the C−N coupling of CO 2 and NO 3 − . By replacing inactive tetrahedral cobalt atoms with copper atoms, the catalytic performance was further enhanced. This study provides key design principles for high‐performance metal oxide catalysts for C−N coupling reactions.