Single atom catalysis for electrocatalytic ammonia synthesis

Ammonia is a vital base molecule for modern agriculture and industry. As the commercially-mature approach for NH3 production, the traditional Haber-Bosch process has achieved great success; however, it also suffers from drawbacks such as massive energy consumption and huge CO2 emissions. The electrocatalytic nitrogen reduction reaction (eNRR) process, powered by intermittent renewable energy, can realize the carbon-neutral and on-site generation of NH3 under mild conditions directly from air/N-2 and water, and has gradually emerged as a multidisciplinary research hotspot. Owing to their advantages such as maximum atom utilization as well as special coordination environment and electronic structure, single atom catalysts (SACs) exhibit great potential in enhancing the faradaic efficiency and ammonia yield rate of the eNRR process. This review analyzes recent theoretical and experimental advances in the development of SACs used for the eNRR, including their synthesis and in situ characterization, as well as the classification and activity of noble metal-, non-noble metal- and nonmetal-based SACs. In addition, we summarize the unique structure and electronic properties of SACs and their enhanced activity in electrochemical reactions, to guide the rational design of efficient catalysts. Finally, we discuss major challenges related to the synthesis of NH(3)via SACs, and outline future prospects in their development.