Synergistic Multisites FeMoS Electrocatalysts for Ambient Nitrogen Conversion to Ammonia.

Electrochemical hydrogenation of N under ambient conditions is attractive for sustainable and distributable NH production but is limited by the lack of selective electrocatalysts. Herein, we describe active site motifs based on the Chevrel phase chalcogenide FeMoS that exhibit intrinsic activities for converting N to NH in aqueous electrolytes. Despite having a very low specific surface area of ∼2 m/g, this catalyst exhibited a Faradaic efficiency of 12.5% and an average rate of 70 μg h mg for NH production at -0.20 V vs RHE. Such activities were attributed to the unique composition and structure of FeMoS that provide synergistic multisites for activating and associating key reaction intermediates. Specifically, Fe/Mo sites assist adsorption and activation of N, whereas S sites stabilize hydrogen intermediate H* for N hydrogenation. Fe in FeMoS enhances binding of S with H* and thus inhibits the competing hydrogen evolution reaction. The spatial geometry of Fe, Mo, and S sites in FeMoS promotes conversion of N-H* association intermediates, reaching a turnover frequency of ∼0.23 s for NH production.