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 μgurea mgcat–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.