Urea Production on Metal-Free Dual Silicon Doped C9N4 Nanosheet Under Ambient Conditions by Electrocatalysis: A First Principles Study

The development of cheap, eco-friendly electrocatalysts for urea synthesis which avoids the traditional nitrogen reduction to form ammonia, is very important to meet our growing demand for urea. Herein, based on density functional theory, we propose a novel electrocatalyst (dual Si doped C₉N₄ nanosheet) composed of totally environmentally benign non-metal earth abundant elements, which is able to adsorb N₂ and CO₂ together. Reduction of CO₂ to CO happens, which is then inserted into activated N−N bond, and it produces *N(CO)N intermediate, which is the crucial step for urea formation. Eventually following several proton coupled electron transfer processes, urea is formed under ambient conditions. The limiting potential value for urea formation is found to be lower than that of NH₃ formation and HER (hydrogen evolution reaction). Moreover, the faradaic efficiency of our proposed catalyst system is 100 % for urea formation, which suggests greater selectivity of urea formation over other competitive reactions.