Structural insight into [Fe–S2–Mo] motif in electrochemical reduction of N2 over Fe1-supported molecular MoS2

Abstract

The catalytic synthesis of NH₃ from the thermodynamically challenging N₂ reduction reaction under mild conditions is currently a significant problem for scientists. Accordingly, herein, we report the development of a nitrogenase-inspired inorganic-based chalcogenide system for the efficient electrochemical conversion of N₂ to NH₃, which is comprised of the basic structure of [Fe–S₂–Mo]. This material showed high activity of 8.7 mg_NH3 mg_Fe⁻¹ h⁻¹ (24 μg_NH3 cm⁻² h⁻¹) with an excellent faradaic efficiency of 27% for the conversion of N₂ to NH₃ in aqueous medium. It was demonstrated that the Fe₁ single atom on [Fe–S₂–Mo] under the optimal negative potential favors the reduction of N₂ to NH₃ over the competitive proton reduction to H₂. Operando X-ray absorption and simulations combined with theoretical DFT calculations provided the first and important insights on the particular electron-mediating and catalytic roles of the [Fe–S₂–Mo] motifs and Fe₁, respectively, on this two-dimensional (2D) molecular layer slab.