Asymmetric Fe single atom on BN for boosted nitrate electroreduction to ammonia

Abstract

The electrochemical nitrate reduction reaction (NO₃RR) is a promising route for sustainable ammonia (NH₃) synthesis and water purification. Herein, we present a novel single-atom catalyst (SAC) featuring an asymmetric FeN₂O₂ site anchored on boron nitride (FeN₂O₂-BN), synthesized via an atmosphere-controlled high-temperature solid-phase method. FeN₂O₂-BN demonstrates an outstanding electrocatalytic performance in the conversion of NO₃⁻ to NH₃, achieving a high faradaic efficiency for NH₃ (FE_NH3) of 94.24% and reaching a remarkable NH₃ yield rate of 8.91 mg h⁻¹ mg_cat⁻¹ at −0.4 V vs. the reversible hydrogen electrode (RHE). Critically, FeN₂O₂-BN exhibits exceptional operational stability over 288 hours of continuous electrolysis while maintaining its structural integrity. In situ characterization and density functional theory (DFT) calculations reveal that the asymmetric FeN₂O₂ site lowers the energy barrier for the rate-determining step (*NO₂ → *NO₂H) and promotes water dissociation to supply protons for the hydrogenation reaction of NO_x. This study highlights the crucial role of precisely engineered asymmetric coordination environments in single-atom catalysts for advanced electrocatalytic applications.