The impact of alkali and alkaline earth metals on green ammonia synthesis

Alkali and alkaline earth metals (AMs) play indispensable roles in dinitrogen activation and ammonia synthesis. AM oxides have been used as catalyst promoters for industrial ammonia synthesis, while AM metals are common reducing agents in dinitrogen fixation by organometallic complexes. With the strong push toward green ammonia synthesis, AM is now on a greater platform, playing a more prominent role in mediating dinitrogen reduction via a variety of processes that can be coupled with renewable energy harvest and storage. This perspective discusses the rich chemistry among AM, N2, H2, and NH3; summarizes the classic understandings and new exciting progress in the exploration of AM for both heterogeneous and homogeneous nitrogen fixation; and highlights the multifunctional roles of unconventional and reactive AM-containing materials for future greener ammonia synthesis.