Synergizing Fe ₂ O ₃ Nanoparticles on Single Atom Fe‐N‐C for Nitrate Reduction to Ammonia at Industrial Current Densities

Abstract The electrochemical reduction of nitrates (NO ₃ ⁻ ) enables a pathway for the carbon neutral synthesis of ammonia (NH ₃ ), via the nitrate reduction reaction (NO ₃ RR), which has been demonstrated at high selectivity. However, to make NH ₃ synthesis cost‐competitive with current technologies, high NH ₃ partial current densities (j _NH3 ) must be achieved to reduce the levelized cost of NH ₃ . Here, the high NO ₃ RR activity of Fe‐based materials is leveraged to synthesize a novel active particle‐active support system with Fe ₂ O ₃ nanoparticles supported on atomically dispersed Fe–N–C. The optimized 3×Fe ₂ O ₃ /Fe–N–C catalyst demonstrates an ultrahigh NO ₃ RR activity, reaching a maximum j _NH3 of 1.95 A cm ⁻² at a Faradaic efficiency (FE) for NH ₃ of 100% and an NH ₃ yield rate over 9 mmol hr ⁻¹ cm ⁻² . Operando XANES and post‐mortem XPS reveal the importance of a pre‐reduction activation step, reducing the surface Fe ₂ O ₃ (Fe ³⁺ ) to highly active Fe ⁰ sites, which are maintained during electrolysis. Durability studies demonstrate the robustness of both the Fe ₂ O ₃ particles and Fe–N _x sites at highly cathodic potentials, maintaining a current of −1.3 A cm ⁻² over 24 hours. This work exhibits an effective and durable active particle‐active support system enhancing the performance of the NO ₃ RR, enabling industrially relevant current densities and near 100% selectivity.