Over 56.55% Faradaic efficiency of ambient ammonia synthesis enabled by positively shifting the reaction potential.

Abstract

Ambient electrochemical N₂ reduction is emerging as a highly promising alternative to the Haber-Bosch process but is typically hampered by a high reaction barrier and competing hydrogen evolution, leading to an extremely low Faradaic efficiency. Here, we demonstrate that under ambient conditions, a single-atom catalyst, iron on nitrogen-doped carbon, could positively shift the ammonia synthesis process to an onset potential of 0.193 V, enabling a dramatically enhanced Faradaic efficiency of 56.55%. The only doublet coupling representing ¹⁵NH₄⁺ in an isotopic labeling experiment confirms reliable NH₃ production data. Molecular dynamics simulations suggest efficient N₂ access to the single-atom iron with only a small energy barrier, which benefits preferential N₂ adsorption instead of H adsorption via a strong exothermic process, as further confirmed by first-principle calculations. The released energy helps promote the following process and the reaction bottleneck, which is widely considered to be the first hydrogenation step, is successfully overcome.