Single-atom catalysts boost nitrogen electroreduction reaction.

Ammonia (NH3) is mainly produced through the traditional Haber-Bosch process under the harsh conditions with huge energy consumption and massive carbon dioxide (CO2) emission. The nitrogen electroreduction reaction (NERR), as an energy-efficient and environment-friendly process converting nitrogen (N2) to NH3 under ambient conditions, has been regarded as a promising alternative to the Haber-Bosch process and has received enormous interest in recent years. Although some exciting progress has been made, considerable scientific and technical challenges still exist in improving the NH3 yield rate and Faradic efficiency, understanding the mechanism and promoting the wide commercialization of NERR. Single-atom catalysts (SACs) have emerged as promising catalysts because of the atomically dispersed activity sites and maximized atom efficiency, unsaturated coordination environment, and the unique electronic structure, which could significantly improve the rate of reaction and yield rate of NH3. In this review we brifely introduce the unique structural and electronic features of SACs, which help to comprehensively understand the mechanism due to their structural simplicity and diversity, and in turn expedites the rational design of fantastic catalysts at the atomic scale. Then we mainly summarize the most recent experimental and computational efforts on developing novel SACs with excellent NERR performance, including precious metal-, nonprecious metal- and nonmetal-based SACs. Finally, the challenges and perspectives of SACs on NERR, as well as some potential means for advanced NERR catalysts are present.