Engineering active sites of cathodic materials for high-performance Zn-nitrogen batteries

As an ideal carbon-free energy carrier, ammonia plays an indispensable role in modern society. The conventional industrial synthesis of NH₃ by the Haber–Bosch technique under harsh reaction conditions results in serious energy consumption and environmental pollution. Therefore, it is essential to develop NH₃ synthesis tactics under benign conditions. Electrochemical synthesis of NH₃ has the advantages of mild reaction conditions and environmental friendliness, and has become a hotspot for research in recent years. It has been reported that zinc-nitrogen batteries (ZNBs), such as Zn-N₂, Zn-NO, Zn-NO₃⁻, and Zn-NO₂⁻ batteries, can not only reduce nitrogenous species to ammonia but also have concomitant power output. However, the common drawbacks of these battery systems are unsatisfactory power density and ammonia production. In this review, the latest progress of ZNBs including the reaction mechanism of the battery and reactor design principles is systematically summarized. Subsequently, active site engineering of cathode catalysts is discussed, including vacancy defects, chemical doping, and heterostructure engineering. Finally, some insights are provided to improve the performance of ZNBs from a practical perspective of view.