Defect engineered electrocatalysts for C–N coupling reactions toward urea synthesis

Urea is extensively used in agriculture and chemical industry, and it is produced on an industrial scale from CO2 and Haber–Bosch NH3 under relatively high temperature and high pressure conditions, which demands high energy input and generates masses of carbon footprint. The conversion of CO2 and N sources（such as NO2-, NO3-, and N2） through electrocatalytic reactions under ambient conditions is a promising alternative to realize efficient urea synthesis. Of note, the design of electrocatalyst is one of the key factors that can improve the efficiency and selectivity of C–N coupling reactions. Defect engineering is an intriguing strategy for regulating the electronic structure and charge density of electrocatalysts,which endows electrocatalysts with excellent physicochemical properties and optimized adsorption energy of the reaction intermediates to reduce the kinetic barriers. In this minireview, recent advances of defect engineered electrocatalysts in urea electrosynthesis from CO2 and various N reactants are firstly introduced. Mechanistic discussions of C–N coupling in these advances are presented, with the aim of directing future investigations on improving the urea yield. Finally, the prospects and challenges of defect engineered electrocatalysts for urea synthesis are discussed. This overview is expected to provide in-depth understanding of structure–reactivity relationship and shed light on future electrocatalytic C–N coupling reactions.