Defect engineering for electrochemical nitrogen reduction reaction to ammonia

Electrochemical nitrogen reduction reaction (NRR) to ammonia (NH3) is considered as a promising alternative for the traditional Haber-Bosch process due to its lower energy consumption under ambient conditions. However, major obstacles still remain in improving the NRR activity and selectivity, mainly arising from the chemical inertness of N-2 molecule, the sluggish reaction kinetics, and the competition between hydrogen evolution reaction (HER) and NRR. The defect engineering can regulate and modify the local coordination environment of electrocatalysts, which could be considered as effective strategies to promote the intrinsic activity. In this review, recent advances on defect engineering of nanostructured electrocatalysts for NRR, including vacancy, doping, single atom, amorphization and high-index facet, are summarized. Particularly, the strategies of defect engineering, the reaction mechanisms, and the reliable NH3 detection methods, are systematically discussed. Finally, the opportunities and challenges towards the rational design and synthesis of advanced electrocatalysts with controlled defects for NRR are proposed.