Fe3+/Fe2+‐Tuned Iron Oxides for Enhanced Interfacial Nitrate Activation Toward Efficient Electrochemical Ammonia Production

The electrochemical nitrate‐to‐ammonia conversion (NO 3 RR) offers a sustainable route for nitrogen utilization, yet its efficiency is limited by poor nitrate adsorption and sluggish reaction kinetics. Here, a mesoporous FeO x electrocatalyst ( meso ‐FeO x ) with dual geometric and electronic optimization is presented for enhanced NO 3 RR performance. Through an in situ electrochemical preactivation strategy (–1.3 V vs. RHE), the resulting FeO x catalyst, meso ‐FeO x ‐e1.3, achieves a great ammonia yield rate of 255.40 μmol cm −2 h −1 with a Faradaic efficiency for ammonia (FE NH3 ) of 91.63% at −1.0 V versus RHE, outperforming most previously reported Fe‐based catalysts. X‐ray photoelectron spectroscopy and theoretical calculations reveal that cathodically tuned Fe 3+ /Fe 2+ redox pairs dynamically regulate the adsorption and activation of nitrate, while the well‐defined mesoporous structure ensures efficient mass transport. This work demonstrates a synergistic design principle—combining nanostructural engineering with dynamic electronic modulation, to enhance the multistep electrocatalysis reaction.