Coupling N2 and CO2 in H2O to synthesize urea under ambient conditions

The urea is an organic compound with a wide range of uses in agriculture, industry and other fields and be well known as an agricultural fertilizer.

In the organic synthesis industry, urea is used to make high polymer synthetic materials; in the pharmaceutical field, it is used as the main raw material or additive to make dozens of chemicals such as furancillin, urea fat; in laboratory applications, urea It is a commonly used protein denaturant, which can effectively destroy non-covalently bound proteins... The wide application of urea brings huge market demand.

Market demand promotes the industrial production of urea，the synthesis of urea mainly uses carbon dioxide (CO₂) and ammonia (NH₃) as raw materials and through two consecutive industrial processes,N₂ + H₂ → NH₃ 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 NH₃ produced globally.

Based on this, Chinese scientists have developed a new urea synthesis method. They directly coupled N₂ and CO₂ in H₂O to produce urea under ambient conditions. The process was carried out using an electrocatalyst consisting of PdCu alloy nanoparticles on TiO₂ 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.

This study provided a completely new method of urea synthesis, avoiding rigorous processes and reducing energy and ammonia consumption in previous production methods.

References: Chen, C., Zhu, X., Wen, X. et al. Coupling N2 and CO2 in H2O to synthesize urea under ambient conditions. Nat. Chem. (2020), DOI: 10.1038/s41557-020-0481 -9