Synergistic electrocatalysis of crystal facet and O-vacancy for enhancive urea synthesis from nitrate and CO2

One-pot green urea electrosynthesis from CO2 and nitrogenous pollutants via the co-reductive C−N coupling route under ambient conditions is prospective to replace the traditional urea synthesis process. Here, a bifunctional indium hydroxide (Vo-S-IO-6) bearing oxygen vacancy (Vo) sites on {100} facets was developed to markedly enable urea synthesis (unprecedented faradaic efficiency of 60.6% with a high production rate of 910.4 μg h-1 mg-1cat.) from NO3− and CO2 by subtly integrating facet and defect engineering. ln-O-x-O-ln (x = C or N) configuration and Vo in Vo-S-IO-6 provided dual active sites for the adsorption and activation of NO3− and CO2 to exclusively form *NO2 and *CO2 species, respectively, which ensured highly selective C−N coupling. Moreover, theoretical calculations elaborated that Vo-induced local electron reconstruction accelerated the protonation rate-determining step, thus lowering overall energy barriers. This work offers a design strategy of synergistic electrocatalysts based on geometrical nature for efficient urea synthesis.