Synergizing Fe <sub>2</sub> O <sub>3</sub> Nanoparticles on Single Atom Fe‐N‐C for Nitrate Reduction to Ammonia at Industrial Current Densities
Eamonn Murphy, Baiyu Sun, Martina Rüscher, Yuanchao Liu, Wenjie Zang, Shengyuan Guo, Yuhan Chen, Uta Hejral, Ying Huang, Alvin Ly, Iryna V. Zenyuk, Xiaoqing Pan, Janis Timoshenko, Beatriz Roldán Cuenya, Erik David Spoerke, Plamen Atanassov
Abstract
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.