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

Abstract

The 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 844.11mg 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.