A Self‐Recycling Ruthenium Incorporated CuFe ₂ O ₄ Electrocatalyst for Efficient Neutral Ammonia Electrosynthesis

Abstract

Abstract The high performance of Fe‐based electrocatalyst for electrochemical nitrate reduction reaction to ammonia (eNO 3 − RR‐to‐NH 3 ) is currently constrained by low NH 3 selectivity and insufficient stability under high current density. Hence, the incorporation of ruthenium single‐atom into the CuFe 2 O 4 (Ru SA ‐CuFe 2 O 4 ) with self‐recycling property is developed. The Cu and Ru sites synergistically promote the water dissociation and facilitate the redeposition of in situ adsorbed Fe 2+ (Fe 2+ ad ) as α‐FeOOH by self‐reinforcing local alkalinity at the Ru SA ‐CuFe 2 O 4 surface, thereby achieving high activity and robust stability for eNO 3 − RR‐to‐NH 3 process. The optimized Ru SA ‐CuFe 2 O 4 delivers excellent performance with a 97.9% NH 3 Faradaic efficiency and 99.8% NH 3 selectivity at −0.59 V versus RHE in neutral electrolyte. Remarkably, in a membrane electrode assembly (MEA) system, it achieves a large current density of 1000 mA cm −2 at 2.5 V with robust stability, accompanied by >95% NH 3 selectivity, a nitrate removal rate of 4.17 mmol h −1  cm −2 , and an NH 3 production rate of 3.97 mmol h −1  cm −2 . Theoretical calculations have demonstrated that Ru site in the Ru SA ‐CuFe 2 O 4 significantly enhances NO 3 − adsorption and lowers the energy barrier for the potential determining step (*HNO 2 → *NO). This work offers valuable insights into designing autonomous local alkalinity microenvironments with self‐recycling properties on cost‐effective Cu/Fe oxides.