Achieving High Activity and Selectivity of Nitrogen Reduction via Fe–N₃ Coordination on Iron Single-Atom Electrocatalysts at Ambient Conditions

Abstract

Electrocatalytic nitrogen reduction reaction (NRR) represents a highly promising process to ammonia synthesis for artificial N2 fixation. However, the yield rate for NH3 production and Faradaic efficiency (FE) are still low, which greatly hinder its widespread applications. Until now, although a variety of catalysts, including single-atom catalysts, have been developed for NRR in the pursuit of suppressing hydrogen evolution reaction (HER) and the corresponding higher FE, the limited NH3 yield rate makes them uncompetitive for the synthesis of ammonia. Herein, we report a Fe single-atom catalyst anchoring on a nitrogen-doped carbon substrate (Fe SAC/N–C) as a highly efficient NRR catalyst. The catalyst achieves a high FE of 39.6% in 0.1 M KOH under room temperature, particularly a dramatically enhanced NH3 yield rate of 53.12 μgNH3 h–1 mgcat–1. The isotopic labeling (15N2) experiment confirms that the NH3 production completely originates from N2 reduction. Meanwhile, theoretical calculations and X-ray fine structure analysis reveal that the Fe–N3 coordination of Fe SAC/N–C is indeed responsible for the suppression of HER, particularly resulting in a maximum activation of NRR intermediates to produce ammonia with a high yield rate.