Electrochemical synthesis of urea on MBenes

Urea is an important raw material in the chemical industry and is widely used as a nitrogen source in chemical fertilizers. The current industrial urea synthesis not only requires harsh reaction conditions, but also consumes most of the NH3 obtained through artificial synthesis. The conversion of N-2 and CO2 into urea through electrochemical reactions under ambient conditions represents a novel green urea synthesis method. However, the large-scale promotion of this method is limited by the lack of suitable electrocatalysts. Here, by means of density functional theory computations, we systematically study the catalytic activity of three experimentally available two-dimensional metal borides (MBenes), Mo2B2, Ti2B2, and Cr2B2 toward simultaneous electrocatalytic coupling of N-2 and CO2 to produce urea under ambient conditions. According to our results, these three MBenes not only have superior intrinsic basal activity for urea formation, with limiting potentials ranging from -0.49 to -0.65eV, but also can significantly suppress the competitive reaction of N-2 reduction to NH3. In particular, 2D Mo2B2 and Cr2B2 possess superior capacity to suppress surface oxidation and self-corrosion under electrochemical reaction conditions, rendering them relatively promising electrocatalysts for urea production. Our work paves the way for the electrochemical synthesis of urea. The conversion of N-2 and CO2 into urea through electrochemical reactions under ambient conditions represents a novel green urea synthesis method. Here, the authors demonstrate that two-dimensional transition metal borides can serve as effective catalysts for electrochemical urea synthesis.