FeMo sub-nanoclusters/single atoms for neutral ammonia electrosynthesis

Electrochemical N₂ reduction reaction (NRR) has long been regarded as a promising process to generate NH₃ under ambient conditions. Therefore, developing cost-effective and high-performance non-noble-metal catalysts for NRR is highly desirable. Inspired by the biological nitrogenase structure, we here designed and synthesized a catalyst with iron-molybdenum sub-nanoclusters and single atoms on porous nitrogen-doped carbon (FeMo/NC). The catalyst features porous structure beneficial to active site exposure and accessibility to electrolyte as well as FeMo sub-nanoclusters and single atoms enabling to activate N₂ molecular. In situ near-ambient pressure X-ray photoelectron spectroscopy tests reveal that during the process from vacuum to nitrogen saturation, N₂ was close to, adsorbed on and interacted with Fe and Mo in FeMo/NC. The Fe and Mo through electron transfer play a key role in activating the N₂ molecules. Therefore, when tested for NRR, FeMo/NC achieves the maximum Faradaic efficiency (FE) of 11.8 ± 0.8% at −0.25 V and NH₃ yield rate of 26.5 ± 0.8 μg h⁻¹ mg_cat.⁻¹ at −0.3 V in neutral electrolyte. Moreover, the catalyst exhibits ignorable variations in the FE and a slight decrease in current density for 100,000 s. This work develops a non-precious bimetallic electrocatalyst with synergetic effect capability for efficient NH₃ production and provides a guideline for the design of efficient and robust catalysts with coexistence of sub-nanoclusters and single atoms.