Recent progress of inorganic metal-based catalysts in electrocatalytic synthesis of ammonia

Ammonia is an indispensable industrial chemical for fertilizer production and energy carriers. Electrocatalytic nitrogen reduction reaction (NRR) shows a promising possibility for converting dinitrogen to ammonia under mild conditions, which is expected to replace the harsh Haber-Bosch process. However, the industrial application of NRR is limited by the low yield and unsatisfactory Faradaic efficiency derived from the poor catalytic activity. Herein, the research progress of reaction principles and possible mechanisms of NRR are summarized, followed by the introduction of conventional ammonia detection methods so as to point out the instructive research directions. Then, the recent advances of different metal-based materials including noble metal and non-noble transition metal–based electrocatalysts for NRR are presented with the corresponding prevailing theoretic calculation results. Additionally, the rational design strategies of various metal-based electrocatalysts are discussed according to the increasing adsorption of N₂, and decreasing activation energy of N₂ reduction reaction, as well as the suppressed hydrogen evolution reaction aiming at enhancing the electrocatalytic performance and Faradaic efficiency. Lastly, the current challenges and future prospects are proposed to shed light on the realization of industrialization.