(667b) Urea Synthesis Via Electrocatalytic Oxidative Coupling of CO with NH3

Electrochemical conversion of CO to valuable chemicals offers an appealing route to store sustainable electricity and repurpose the major greenhouse gas CO₂. Among the potential products, chemical containing C-N bonds such as urea is particularly attractive due to its importance in agricultural, chemical and pharmaceutical industries. Previous research has primarily focused on cathodic reactions, which are impeded by the competing hydrogen evolution reaction and limited electron efficiency. In this talk, we discuss a urea synthesis approach via electrocatalytic oxidative coupling between CO and NH₃ on commercial Pt catalysts. We demonstrate an optimal Faradaic efficiency of approximately 70% for electrocatalytic C-N bond formation and remain above 50% throughout the entire potential window explored with an electrocatalytic C-N bond formation rate of up to 100 mmol×h^-1×g_catalyst^-1. Through combined experimental and computational investigations, we propose that the oxidative coupling of CO and NH₃ on Pt leads to the formation of cyanate, which then undergoes the Wöhler reaction to form urea. Our approach affords a high electron efficiency and low energy consumption compared to urea formation in the current industrial process and co-reduction of CO₂ and nitrate. From the perspective of fundamental electrocatalytic research, the electro-oxidative coupling pathway developed in this study highlights the opportunity of employing Pt as an active and selective catalyst in the presence of well-known poison species, i.e., CO and NH₃.