Recent Advances in Electrocatalysts for Sustainable Electrosynthesis of Ammonia and Urea from Ambient Nitrite Reduction and C–N Coupling

The global nitrogen cycle has been destroyed by the quickly growing anthropogenic emissions of nitrite-containing pollutants during the past decades, which causes numerous unexpected environmental side effects and threatens human health. Compared with conventional nitrite removal methods featuring low efficiency, high cost, and secondary pollution, the electrocatalytic nitrite reduction reaction has garnered significant attention and offers an appealing solution for nitrite removal and recovering the global nitrogen balance. Moreover, it takes a step further to convert nitrite into recyclable nitrogen-containing fertilizer including ammonia and urea. However, the materials design and mechanistic aspects for such emerging complex reactions are yet to be explored compared to other well-studied primary reactions such as oxygen reduction and water splitting. To address this challenge, this review provides a comprehensive account of a sustainable electrosynthesis of ammonia and urea from ambient nitrite reduction and C–N coupling. The two key reactions, namely ammonia production from the nitrite reduction reaction and urea synthesis from coreduction of nitrite and carbon dioxide, are elaborated in detail, with available catalysts as the focus of the discussion. The current technical barriers and potential research prospects in this domain, including exploring excellent electrocatalysts with high activity and selectivity, precisely controlling the interfacial microenvironment, and understanding in-depth the reaction mechanism, are highlighted.