Synergy between Fe and Mo single atom catalysts for ammonia electrosynthesis

Electrochemical nitrate to ammonia conversion provides an eco-friendly route for a highly valued product. However, nitrite intermediate formation and hydrogen evolution competition hinder full conversion. Here, we implement a Fe-Mo dual single-atom catalyst where the two metals work in tandem to achieve nitrate to ammonia conversion with excellent activity and stability, an ammonia yield rate of up to 13.56 mg cm−2 h−1 and a Faradaic efficiency up to 94%. In-situ Raman and Fourier-transform infrared spectroscopy confirms nitrite as the intermediate bound to metal sites. Time-dependent detection of products and DFT calculations support a tandem mechanism: the Mo single atoms are the preferred sites for the conversion of nitrate to nitrite, while the Fe single atoms catalyze the further conversion of nitrite to ammonia. This discovery paves the way for energy-relevant transformations using bimetallic single-atom catalysts.