Urea (CO(NH 2 ) 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 CO 2 and nitrogen species including NO 3

− , NO 2 -, NO, and N 2 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 CO 2 /nitrogen sources has received

huge attention, yet its low Faradaic effi ciency, 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 CO 2 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 effi cient C–N coupling for

highly sustainable urea production.