Zn single atom on N-doped carbon: Highly active and selective catalyst for electrochemical reduction of nitrate to ammonia

Electrochemical reduction of nitrate (NO3−) to ammonia (NH3) in aqueous media is a double-advantage process, which can convert the main pollutant in water to the most useful chemical feedstocks. However, the design and development of highly effective and selective catalyst for NO3− reduction reaction (NO3−RR) is still challenging currently, as the NO3−RR contains multiple pathways and suppresses each other. Here, we demonstrate a highly active and selective Zn single atom supported microporous N-doped carbon catalyst, which was characterized by the atomic resolution high-angle annular dark field-scanning transmission electron microscopy, achieving excellent NO3−RR performance (NO3− conversion: 97.2 %; NH3 selectivity: 94.9 %; NH3 yield rate: ∼39,000 μg h−1 mgcat.−1; Faradaic efficiency: 94.8 %). Density functional theory calculations confirm that the atomically dispersed Zn atom coordinated with four N atoms has moderate interaction with NO3− species due to its positive charge. The reaction mechanism and potential determining step for NO3−RR on single Zn atom were further determined. This research provides an exciting new way for the rational design and development of single atom catalyst for advanced electrochemical applications.