Phosphorization of α‐Fe2O3 Boosts Active Hydrogen Mediated Electrochemical Nitrate Reduction to Ammonia

Abstract Inexpensive iron‐based materials are considered promising electrocatalysts for nitrate (NO 3 − ) reduction, but their catalytic activity and spontaneous corrosion remain challenges. Here, the α‐Fe 2 O 3 active surface is reconstructed by gradient phosphorization to obtain FeP x with higher electrochemical activity. FeP 2.0 optimizes the adsorption energy of NO 3 − and its reduction intermediates, meanwhile promote the generation of active hydrogen ( * H) but inhibit its generation of H 2 . More importantly, Fe and P can serve as binding sites for NO 3 − and * H, respectively, which improves the electron utilization of NO 3 − deoxygenation and the efficiency of the subsequent hydrogenation for the selective synthesis of NH 3 . 91.7% NO 3 − conversion rate is achieved for the reduction of 100 mL 200 mg L −1 NO 3 − −N, 99.3% ammonia (NH 3 selectivity (yield of 1.79 mg h −1 cm −2 ), and 91.4% Faraday efficiency in 3 h. The high‐purity solid NH 4 Cl is finally extracted by gas extraction and vacuum distillation (81.4% recovery). This study provides new insights and strategies for the conversion of NO 3 − to NH 3 products over iron‐based electrocatalysts.