Coupling N-2 and CO2 in H2O to synthesize urea under ambient conditions

摘要

The use of nitrogen fertilizers has been estimated to have supported 27% of the world's population over the past century. Urea (CO(NH2)(2)) is conventionally synthesized through two consecutive industrial processes, N-2 + H-2 -> NH(3)followed by NH3 + CO2 -> urea. Both reactions operate under harsh conditions and consume more than 2% of the world's energy. Urea synthesis consumes approximately 80% of the NH(3)produced globally. Here we directly coupled N(2)and CO(2)in H2O to produce urea under ambient conditions. The process was carried out using an electrocatalyst consisting of PdCu alloy nanoparticles on TiO(2)nanosheets. This coupling reaction occurs through the formation of C-N bonds via the thermodynamically spontaneous reaction between *N=N* and CO. Products were identified and quantified using isotope labelling and the mechanism investigated using isotope-labelled operando synchrotron-radiation Fourier transform infrared spectroscopy. A high rate of urea formation of 3.36 mmol g(-1) h(-1) and corresponding Faradic efficiency of 8.92% were measured at -0.4 V versus reversible hydrogen electrode.