Tailoring Atomic Metal Species for Electrochemical-Driven Urea Synthesis Coupled with CO₂ and Nitrogen Sources in Aqueous Media

Urea (CO(NH₂)₂) is an essential chemical compound for human being, however, the current predominant industrial method for the production of urea is the Bosch–Meiser process, which requires a large amount of energy with harsh conditions including high temperature (400–500 °C) and high pressure (150–300 bar). The electrochemical synthesis of urea via reduction reactions coupled with CO₂ and nitrogen species including NO₃⁻, NO₂-, NO, and N₂ provides a promising solution to realize carbon neutrality as well as valorization of waste nitrogen source. In order to produce urea under ambient conditions in aqueous electrolyte, electrochemical and photoelectrochemical C–N coupling of these CO₂/nitrogen sources has received huge attention, yet its low Faradaic efficiency, low urea yield rate, and ambiguous C–N coupling reaction mechanism remain the major obstacles to scale-up process. Herein, we present the reaction mechanism of urea synthesis with CO₂ and nitrogenous, the methodology for detecting and quantifying the produced urea over other byproducts, and recent progress on electrochemical and photoelectrochemical urea synthesis with the rational design of metal nanocatalysts. Furthermore, we examine the current challenges and insights associated with the urea synthesis to facilitate efficient C–N coupling for highly sustainable urea production.