Synergistic Multisites Fe2Mo6S8 Electrocatalysts for Ambient Nitrogen Conversion to Ammonia

Electrochemical hydrogenation of N 2 under ambient conditions is attractive for sustainable and distributable NH 3 production but is limited by the lack of selective electrocatalysts. Herein, we describe active site motifs based on the Chevrel phase chalcogenide Fe 2 Mo 6 S 8 hat exhibit intrinsic activities for converting N 2 o NH 3 in aqueous electrolytes. Despite having a very low specific surface area of ∼2 m 2 /g, this catalyst exhibited a Faradaic efficiency of 12.5% and an average rate of 70 μg h -1 mg ca -1 for NH 3 production at -0.20 V vs RHE. Such activities were attributed to the unique composition and structure of Fe 2 Mo 6 S 8 hat provide synergistic multisites for activating and associating key reaction intermediates. Specifically, Fe/Mo sites assist adsorption and activation of N 2 , whereas S sites stabilize hydrogen intermediate H ad * for N 2 hydrogenation. Fe in Fe 2 Mo 6 S 8 enhances binding of S with H ad * and thus inhibits the competing hydrogen evolution reaction. The spatial geometry of Fe, Mo, and S sites in Fe 2 Mo 6 S 8 promotes conversion of N 2 -H ad * association intermediates, reaching a turnover frequency of ∼0.23 s -1 for NH 3 production.