Ambient Electrochemical Ammonia Synthesis From Various Nitrogen Sources.

Ammonia is a vital chemical feedstock for agriculture and energy storage. However, conventional ammonia synthesis via the Haber-Bosch process is both energy-intensive and carbon-intensive, and therefore, developing sustainable alternatives is critical. This review discusses recent progress for the electrochemical production of ammonia from various nitrogen sources under ambient conditions. Both nitrogen conversion and the conversion of reactive nitrogen oxides (nitrate, nitrite, and nitric oxide) have been explored but face major drawbacks, such as low yields, competing side reactions, such as hydrogen evolution, a high activation barrier, and complex multi-electron/proton pathways. This review first discusses the recent progress in this field from a material standpoint to improve the selectivity and yield towards ammonia. Then, the improvements in critical areas beyond material development are discussed in depth, such as ammonia detection and reactor design. Finally, nitrogen, nitrate/nitrite, and nitric oxide reduction routes are assessed to identify the most promising path to sustainable, scalable green ammonia production. Altogether, more innovations are needed to develop efficient and scalable electrochemical NH3 synthesis technologies that can supplement, or eventually replace, the Haber-Bosch process.