Atomically dispersed iron & iron clusters synergistically accelerate electrocatalytic ammonia synthesis

Abstract

Green energy-driven electrochemical-nitrate-reduction-reaction (eNitRR) provides an alternative pathway for sustainable ammonia synthesis, but there is still a lack of reliable catalyst. Herein, through the combination of coordination confinement and spatial confinement, single-atom Fe and Fe clusters were simultaneously embedded on nitrogen-doped-hollow-carbon-tubes (Fe/NHCTs) to cooperatively promote the highly selective conversion of nitrate to ammonia in complex water environments. The ammonia yield rate reached 45595.63 μg h⁻¹ mg⁻¹ with Faradaic efficiency close to 100 %. The Zn-nitrate battery with Fe/NHCTs as the core has a high open circuit voltage and power density, and can output electric energy for a long time while highly selective synthesis of ammonia. The pathway and hydrogenation mechanism of nitrate evolution to ammonia were revealed using the in-situ attenuated total reflection Fourier-transform infrared, online differential-electrochemical-mass-spectrometry and density functional theory calculations, the intermodulation of electrons between single-atom Fe and Fe clusters synergistically accelerates the conversion of nitrate to ammonia.