Electrocatalytic nitrate reduction: Selectivity at the crossroads between ammonia and nitrogen

Recent years have seen considerable growth in the development of the electrocatalytic nitrate reduction reaction (NO3RR), with the desire for value-added products of ammonia or denitrification-derived harmless N2. However, these were typically discussed within the contexts of either energy crisis or environmental catalysis, leading to few discussions on the selectivity between N–N bond formation and NH3 synthesis. Herein, we review recent progress in the NO3RR for different products of NH3 and N2, placing emphasis on the reaction mechanisms and the vital factors governing selectivity and pathways. The principles to design advanced electrocatalysts with high selectivity are also put forward, followed by a summary of challenges and perspectives pertaining to this topic. This critical review provides significant insights into the crossroads between NH3 synthesis and N2 formation in the electrocatalytic NO3RR, contributing to the mechanisms of understanding and future developments in this field.