Plasmon-Driven Urea Photosynthesis on a Rationally Designed RuCu Nanoalloy Cocatalyst Through a Kinetically Favorable C–N Coupling Mechanism

Abstract Photocatalytic urea synthesis from N2 and CO2 offers a sustainable alternative to the energy-intensive industrial process. However, the efficiency remains hindered by the sluggish C–N coupling kinetics. Herein, a new, kinetically favorable urea synthesis pathway is achieved by a rationally designed RuCu alloy/plasmonic WO3–x hybrid photocatalyst. A remarkable urea production rate of 750 μg gcat–1 h–1 together with a solar-to-chemical conversion efficiency of 0.072% is obtained under simulated sunlight illumination, outperforming those of most reported systems. Unlike commonly studied C–N coupling involving *CO and *N2, a new mechanism is proposed. This mechanism activates and reduces N2 and CO2 into the *NH2NH2 and *CO, respectively, followed by two successive C–N coupling processes to form urea with substantially reduced kinetic barriers. The RuCu alloy demonstrates a much lower energy barrier compared to pure metals, which is attributed to its optimized electronic structure and enhanced intermediate adsorption properties enabled by the intersite synergistic effect within the alloy.