Creating Highly Active Iron Sites in Electrochemical N2 Reduction by Fabricating Strongly-Coupled Interfaces.

Electrochemical Nc reduction has been regarded as one of the most promising approaches to producing ammonia under mild conditions, but there are remaining pressing challenges in improving the reaction rate and efficiency. Herein, an unconventional galvanic replacement reaction is reported to fabricate a unique hierarchical structure composed of Fe3 O4 -CeO2 bimetallic nanotubes covered by Fe2 O3 ultrathin nanosheets. Control experiments reveal that CeO2 species play the essential role of stabilizer for Fe2+ cations. Compared with bare CeO2 and Fe2 O3 nanotubes, the as-obtained Fe2 O3 /Fe3 O4 -CeO2 possesses a remarkably enhanced NH3 yield rate (30.9 µg h-1 mgcat -1 ) and Faradaic efficiency (26.3%). The enhancement can be attributed to the hierarchical feature that makes electrodes more easily to contact with electrolytes. More importantly, as verified by density functional theory calculations, the generation of Fe2 O3 -Fe3 O4 heterogeneous junctions can efficiently optimize the reaction pathways, and the energy barrier of the potential determining step (the *N2 hydrogenates into *N*NH) is significantly decreased.