Direct Electrosynthesis of Urea from Carbon Dioxide and Nitric Oxide

Abstract

Electrochemical synthesis of urea provides a sustainable strategy that can be easily incorporated into currently distributed renewable energy systems. The main challenge that hindered the advancement of this technique lies in developing advanced electrocatalytic processes to utilize abundant and low-cost inorganic carbon and nitrogen sources for highly productive urea generation. Herein, we report an electrocatalytic reaction that converts carbon dioxide (CO 2 ) and nitric oxide (NO) into urea, with water as the hydrogen source, under ambient conditions. The yield rate and Faradaic efficiency of urea reach 15.13 mmol g −1 h −1 and 11.26% at a current density of 40 mA cm −2 under optimized conditions. The critical intermediates of *CO and *NH 2 for urea generation are obtained via the co-reduction of CO 2 and NO and then continuously interconnect to form the C−N bond. A preliminary techno-economic study is performed to discuss the practical application potential of this strategy for urea production.

A Reliable and Precise Protocol for Urea Quantification in Photo/Electrocatalysis

“…Furthermore, HPLC exhibited a broad linear scope from ≈0.005–0.5 to 50 µg mL −1 according to the reported studies. [ 9,51 ] Based on the above results, the EQM of aforesaid detection methods is summarized in Figure 2g. Compared to adjustable EQM of 1 H‐NMR and HPLC methods, urease and DAMO‐TSC methods present a low enough and comparable EQM, which may be more accessible and widely used in the routine quantification (as presented in Figure 1c), particularly explored below.…”

“…Notably, the solution pH, metal ions, and high concentration of ammonia can also affect the accuracy of the urease method. [ 9 ] Combined with the uncertainty of ammonia detection under complex photo/electrocatalysis, the low‐concentration quantification of urea via this kind of urea hydrolysis to the ammonia approach is operated meticulously and challenging.…”

Structure‐Function Correlation and Dynamic Restructuring of Cu for Highly Efficient Electrochemical CO2 Conversion

“…[130] At the same time, electrocatalytic synthesis of CÀ N bonds provides an alternative route to mitigate the accumulation of pollutants, such CO 2 , NO 3 À , and NO x , and to recycle those harmful small molecules into value-added chemicals and fuels under ambient conditions with renewable energy. [131][132][133][134] In this co-electrocatalysis system, the products from Cu-based CO 2 R are key intermediates to form more complex chemicals with CÀ N bonds, such as urea, amides, and nitriles. In the future, this strategy will definitely expand the scope of products available form Cubased CO 2 R. To conclude, in-depth atomistic insight into the complexity of Cu-based CO 2 R reduction, including their structure-function correlation and dynamic restructuring under operation conditions, is critically important to understand CO 2 R mechanisms and further design more efficient catalytic systems.…”

“…In contrast to simple carbon species, the C−N chemicals are more desirable due to their widespread application in the production of bulk chemicals, synthetic intermediates, fertilizers, agrochemicals, and pharmaceuticals [130] . At the same time, electrocatalytic synthesis of C−N bonds provides an alternative route to mitigate the accumulation of pollutants, such CO 2 , NO 3 − , and NO x , and to recycle those harmful small molecules into value‐added chemicals and fuels under ambient conditions with renewable energy [131–134] . In this co‐electrocatalysis system, the products from Cu‐based CO 2 R are key intermediates to form more complex chemicals with C−N bonds, such as urea, amides, and nitriles.…”

Understanding the Site‐Selective Electrocatalytic Co‐Reduction Mechanism for Green Urea Synthesis Using Copper Phthalocyanine Nanotubes

“…and CO 2 through the formation of CN bond coupling. [ 14,17–24 ] And finally, for the suppression of hydrogen evolution reaction (HER), choice of electrolyte and catalyst are very crucial for electrochemical urea synthesis. [ 14 ] In this regard, electrocatalyst having multiple active sites and selectivity toward both nitrogen reduction reaction (NRR) and carbon dioxide reduction reaction under the similar potential window may be effective for urea synthesis in water medium at standard temperature and pressure (STP).…”