Defect engineering for electrocatalytic nitrogen reduction reaction at ambient conditions

Electrochemical nitrogen (N-2) reduction has become as an energy-saving and eco-friendly alternative to Haber-Bosch processes for sustainable ammonia (NH3) synthesis at ambient. In recent years, the synthesis of NH3 from N-2 and water (H2O) in aqueous media is one of the most attractive topics in the field of electrochemistry. To date, to achieve both high catalytic performance and selectivity, the enhancement of activity is usually attributed to the high specific surface area, unique facet structure, enhanced conductivity, and even unclear synergistic effects. However, the importance of defects, especially intrinsic defects, is often overlooked. Recently, the importance of defects in electrocatalytic ammonia synthesis has been demonstrated, and the study on this aspect is becoming a hot topic in the field. In order to have an overview on the influence of defects on the performance of electrochemical synthesis of NH3, this paper introduces the latest development of the concept of using defects, including oxygen-vacancy defects, nitrogen-vacancy defects, sulfur-vacancy defects and carbon-vacancy defects, to enhance the performance of electrocatalytic nitrogen reduction reaction (NRR). Finally, the prospect of further pathways of designing catalysts for NRR with defect engineering is given. (C) 2020 Elsevier B.V. All rights reserved.