Tandem Catalysts Enabling Efficient C−N Coupling toward the Electrosynthesis of Urea

Abstract

AbstractThe development of a methodology for synthesizing value‐added urea (CO(NH2)2) via a renewable electricity‐driven C−N coupling reaction under mild conditions is highly anticipated. However, the complex catalytic active sites that act on the carbon and nitrogen species make the reaction mechanism unclear, resulting in a low efficiency of C−N coupling from the co‐reduction of carbon dioxide (CO2) and nitrate (NO3−). Herein, we propose a novel tandem catalyst of Mo‐PCN‐222(Co), in which the Mo sites serve to facilitate nitrate reduction to the *NH2 intermediate, while the Co sites enhance CO2 reduction to carbonic oxide (CO), thus synergistically promoting C−N coupling. The synthesized Mo‐PCN‐222(Co) catalyst exhibited a noteworthy urea yield rate of 844.11 mg h−1 g−1, alongside a corresponding Faradaic efficiency of 33.90 % at −0.4 V vs. reversible hydrogen electrode (RHE). By combining in situ spectroscopic techniques with density functional theory calculations, we demonstrate that efficient C−N coupling is attributed to a tandem system in which the *NH2 and *CO intermediates produced by the Mo and Co active sites of Mo‐PCN‐222(Co) stabilize the formation of the *CONH2 intermediate. This study provides an effective avenue for the design and synthesis of tandem catalysts for electrocatalytic urea synthesis.