posted on 2021-10-06, 11:36authored byKe Lu, Fan Xia, Bomin Li, Yuzi Liu, Iddrisu B. Abdul Razak, Siyuan Gao, Jacob Kaelin, Dennis E. Brown, Yingwen Cheng
Electrochemical hydrogenation of
N2 under ambient conditions
is attractive for sustainable and distributable NH3 production
but is limited by the lack of selective electrocatalysts. Herein,
we describe active site motifs based on the Chevrel phase chalcogenide
Fe2Mo6S8 that exhibit intrinsic activities
for converting N2 to NH3 in aqueous electrolytes.
Despite having a very low specific surface area of ∼2 m2/g, this catalyst exhibited a Faradaic efficiency of 12.5%
and an average rate of 70 μg h–1 mgcat–1 for NH3 production at −0.20
V vs RHE. Such activities were attributed to the unique composition
and structure of Fe2Mo6S8 that provide
synergistic multisites for activating and associating key reaction
intermediates. Specifically, Fe/Mo sites assist adsorption and activation
of N2, whereas S sites stabilize hydrogen intermediate
Had* for N2 hydrogenation. Fe in Fe2Mo6S8 enhances binding of S with Had* and thus inhibits the competing hydrogen evolution reaction. The
spatial geometry of Fe, Mo, and S sites in Fe2Mo6S8 promotes conversion of N2–Had* association intermediates, reaching a turnover frequency of ∼0.23
s–1 for NH3 production.