Electrocatalytic Oxidative Coupling of CO with NH3: The Role of Surface Oxygenated Species on Catalysts

Abstract

Electrocatalytic synthesis of urea from carbon dioxide/monoxide and nitrogenous small molecules presents a sustainable alternative to the conventional energy-intensive process. Although reductive C–N coupling routes have been extensively explored, the mechanism of electrochemical oxidative synthesis of urea from CO and NH3 remains unclear. Herein, we employ density functional theory calculations combined with constant-potential kinetic simulations to unravel the mechanism of this C–N coupling reaction in oxidative condition. By the surface Pourbaix diagram and activity trend analysis, we demonstrate that the surface oxygenated species presenting on anode catalysts are crucial for activity evaluation. The kinetic analysis reveals that the O*/OH*-covered Pt surface serves as the true active site, and the coupling between CO* and NH2* is favorable for the formation of the C–N bond. Guided by these mechanistic insights, we finally predict ZnPd alloy as a promising catalyst beyond Pt for electrocatalytic oxidative synthesis of urea from CO and NH3, which exhibits an ultralow C–N coupling barrier of 0.07 eV.