Creating Highly Active Iron Sites in Electrochemical N 2 Reduction by Fabricating Strongly-Coupled Interfaces.

Electrochemical N c 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 Fe 3 O 4 -CeO 2 bimetallic nanotubes covered by Fe 2 O 3 ultrathin nanosheets. Control experiments reveal that CeO 2 species play the essential role of stabilizer for Fe 2+ cations. Compared with bare CeO 2 and Fe 2 O 3 nanotubes, the as-obtained Fe 2 O 3 /Fe 3 O 4 -CeO 2 possesses a remarkably enhanced NH 3 yield rate (30.9 µg h -1 mg cat -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 Fe 2 O 3 -Fe 3 O 4 heterogeneous junctions can efficiently optimize the reaction pathways, and the energy barrier of the potential determining step (the *N 2 hydrogenates into *N*NH) is significantly decreased.