Tailoring Activation Intermediates of CO2 Initiates C–N Coupling for Highly Selective Urea Electrosynthesis

Abstract

Electrocatalyzed reduction of CO₂ and NO₃^– to synthesize urea is a highly desirable, but challenging reaction. The bottleneck of this reaction is the C–N coupling of CO₂ and NO₃^– reduction intermediates. In particular, the uncertainty of CO₂ multielectron reduction intermediates severely affects the selectivity and activity of C–N coupling processes involving multiple electron and proton transfers. Here, we present a novel tandem catalyst with two compatible single-atom active sites of Au and Cu on red phosphorus (RP-AuCu) that efficiently converts CO₂ and NO₃^– to urea. Experimental and theoretical prediction results confirmed that the active center of Au on red phosphorus promotes electron transfer between CO₂ molecules and red phosphorus, thereby regulating CO₂ activation intermediates to produce electrophilic *COOH. In addition, the active center of Cu on red phosphorus can enhance the electrophilic attack of *COOH species on *NH₂, thus promoting the selective formation of C–N bonds. Consequently, RP-AuCu exhibited a urea yield of 22.9 mmol g_cat.^–1 h^–1 and a Faraday efficiency of 88.5% (−0.6 V_RHE), representing one of the highest levels of electrocatalytic urea synthesis. This work deepens the understanding of the C–N coupling mechanism and provides an interesting catalyst design approach for the efficient and sustainable production of C–N compounds.