Theoretical Design of the Electrocatalytic Urea Synthesis\nfrom Carbon Dioxide and Nitric Oxides

Recently,\nelectrochemical coreduction of CO<sub>2</sub> and NO<sub><i>x</i></sub> has been proposed as a sustainable route\nfor urea synthesis. Although Zn is the best monometallic catalyst,\nthe urea selectivity on Zn is very low. Toward the rational design\nof catalysts, the reaction mechanism of urea synthesis was unveiled\nbased on an “electric field controlling constant potential”\nmethod, which can directly address the effects of explicit solvent,\nelectric field, and electrode potential on reaction intermediates\nand transition states. We found that the couplings between CO* and\nNOH* and CONH* and N* are most favorable for the formation of two\nC–N bonds of urea, respectively. According to this mechanism,\nwe not only reproduced the experimental Faradaic efficiencies of different\nproducts on Zn but also rationalized the activity trend of urea synthesis\nover a set of catalysts. More interestingly, we have revealed that\nadsorbed N* species on Fe and Mo have an essential promotion on urea\nproduction. Guided by the mechanistic insights, we finally proposed\na compressive strain engineering to tune the d-band center of Zn,\nwhich can decrease the two C–N coupling barriers to 0.06 and\n0 eV, respectively, and deliver a remarkable urea Faradaic efficiency\n(FE) of 88.5% using CO and NO as reactants.