Structure-activity relationship of defective electrocatalysts for nitrogen fixation

Ammonia(NH_(3)), as an important chemical substance and clean energy carrier, plays an indispensable role in industrial and agricultural production. The electrocatalytic synthesis of NH+3 under mild conditions has attracted worldwide attention in the energy field due to its environmental friendliness and cost efficiency,but unsatisfactory NH_(3) yields and Faradaic efficiencies are restricting its development. The introduction of defect has been demonstrated as a feasible way to overcome the disadvantages of electrochemistry, as it can regulate the electronic structure and modulate coordination environment of electrocatalysts, which further create active sites and enhance nitrogen adsorption. In this regard, it is necessary to understand the effects of various types of defects on electrocatalysts based on the latest progress in the defect engineering for nitrogen reduction reaction(NRR). In this review, the concept, classifications, and characterization of defects as well as the approaches to create them in electrocatalysts are firstly discussed.Then, certain types of defects(vacancy, dopant, amorphism, edge/corner, and porousness) affecting the performances of various electrocatalysts are further described. Finally, the summary and challenges of electrocatalytic ammonia synthesis are proposed to design advanced electrocatalysts with high efficiency.