From Inert N2 to Reactive Nitrate: A Comparative Analysis on Electrocatalytic Urea Synthesis via CO2 Coelectrolysis

Electrochemical urea synthesis through C-N bond formation under mild conditions has emerged as a promising alternative to the conventional energy-intensive Bosch-Meiser process, offering a sustainable pathway coupling carbon and nitrogen cycles. In this context, the coelectrolysis of CO2 with different nitrogen sources, N2 and NO3-, has attracted increasing attention. However, these routes present fundamentally distinct challenges and opportunities regarding substrate activation, intermediate formation, and product selectivity. This mini-review provides a comprehensive comparison between N2 + CO2 and NO3- + CO2 coelectrolysis, focusing on the key factors that drive C-N coupling. Intrinsically limitations associated with the high-energy activation for breaking the N≡N triple bond of N2 and its associated low solubility, in contrast with the higher reactivity and availability of NO3- species, were discussed. Mechanistic insights into C-N coupling pathways were critically analyzed, highlighting the role of adsorbed intermediates and competing reactions such as hydrogen evolution and side products from nitrogen-species reduction. Furthermore, recent advances regarding the catalyst design and operational conditions were evaluated in terms of their ability to enhance selectivity toward urea synthesis. Finally, we outline the current challenges and future perspectives for the rational development of next-generation catalytic systems for sustainable urea synthesis.