Synergizing Fe2O3 Nanoparticles on Single Atom Fe‐N‐C for Nitrate Reduction to Ammonia at Industrial Current Densities

Abstract

AbstractThe electrochemical reduction of nitrates (NO3−) enables a pathway for the carbon neutral synthesis of ammonia (NH3), via the nitrate reduction reaction (NO3RR), which has been demonstrated at high selectivity. However, to make NH3 synthesis cost‐competitive with current technologies, high NH3 partial current densities (jNH3) must be achieved to reduce the levelized cost of NH3. Here, the high NO3RR activity of Fe‐based materials is leveraged to synthesize a novel active particle‐active support system with Fe2O3 nanoparticles supported on atomically dispersed Fe–N–C. The optimized 3×Fe2O3/Fe–N–C catalyst demonstrates an ultrahigh NO3RR activity, reaching a maximum jNH3 of 1.95 A cm−2 at a Faradaic efficiency (FE) for NH3 of 100% and an NH3 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 Fe2O3 (Fe3+) to highly active Fe0 sites, which are maintained during electrolysis. Durability studies demonstrate the robustness of both the Fe2O3 particles and Fe–Nx 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 NO3RR, enabling industrially relevant current densities and near 100% selectivity.