Synergistic Bimetallic Sites in 2D-on-2D Heterostructures for Enhanced C-N Coupling in Sustainable Urea Synthesis

Electrochemical conversion of CO₂ and N₂ to produce “green urea” using renewable energy represents a promising avenue for CO₂ mitigation. A bifunctional electrocatalyst with a desirable composition and structure is highly required for the electrochemical reduction of CO₂ and N₂ (CO₂N₂RR) into urea. Herein, Ru-Pd alloyed nanoparticles were successfully incorporated into 2D WO₃ and MXene nanosheets, resulting in the formation of Ru-Pd/WO₃/MXene heterostructures. The catalyst significantly enhances electrocatalytic C-N coupling in CO₂ and N₂ reduction, resulting in increased urea yield. The electrochemical reduction initially converts CO₂ into *CO, which then undergoes direct coupling with N₂ to form urea through continuous protonation. Simultaneously, water molecules are oxidized on the bifunctional Ru-Pd/WO₃/MXene electrodes. The mechanism of C-N coupling for urea formation is elucidated through density functional theory (DFT) calculations. The Ru-Pd/WO₃/MXene catalyst exhibits a noteworthy urea yield of 227 μg_urea mg_cat^-1h^-1 with a faradaic efficiency of 23.7%. The detailed understanding of the CO₂N₂RR mechanism and the recyclable properties of the electrode emphasizes its suitability for prolonged use. This study not only presents a road map for advancing electrolysis but also provides profound insights into the fundamental chemistry of C-N coupling reactions.