Non-metal boron atoms on a CuB12 monolayer as efficient catalytic sites for urea production

Abstract

An electrocatalytic C–N coupling reaction to convert CO₂ and N₂ into urea under mild conditions has been proposed to be a promising alternative experimentally, but the development of highly stable, low-cost and high-performance non-metal catalytic sites remains rare and challenging. Herein, a global-minimum CuB₁₂ monolayer with superior stability has been identified based on first-principles computations, and the most significant finding is that the CuB₁₂ monolayer possesses the best catalytic activity among the reported urea catalysts thermodynamically and kinetically. All possible reaction pathways to form urea (NH₂CONH₂) starting from the CO₂ molecule and N₂ molecule, including the CO₂ pathway, OCOH pathway, CO pathway, NCON pathway and mixed pathway, as well as the kinetic energy barriers of six possible C–N coupling reactions are systematically investigated. Non-metal B atoms at the midpoint of the edges of the squares act as excellent catalytic sites with a limiting potential of urea production of 0.23 V through the CO₂ pathway and OCOH pathway and the lowest kinetic energy barrier of C–N bond formation (0.54 eV) through the reaction *CO + *NHNH → *NHCONH. Therefore, this study not only identifies the first non-metal B catalytic sites for urea formation, but also perfects the reaction mechanism to convert CO₂ and N₂ into urea, which could provide great guiding significance to explore other high-performance urea catalysts.