Constructing Oxygen Vacancies via Engineering Heterostructured Fe₃C/Fe₃O₄ Catalysts for Electrochemical Ammonia Synthesis

Electrocatalytic nitrogen reduction reaction (NRR) under ambient conditions provides an intriguing pathway to convert N₂ into NH₃. However, significant kinetic barriers of the NRR at low temperatures in desirable aqueous electrolytes remain a grand challenge due to the inert N≡N bond of the N₂ molecule. Herein, we propose a unique strategy for in situ oxygen vacancy construction to address the significant trade-off between N₂ adsorption and NH₃ desorption by building a hollow shell structured Fe₃C/Fe₃O₄ heterojunction coated with carbon frameworks (Fe₃C/Fe₃O₄@C). In the heterostructure, the Fe₃C triggers the oxygen vacancies of the Fe₃O₄ component, which are likely active sites for the NRR. The design could optimize the adsorption strength of the N₂ and N_xH_y intermediates, thus boosting the catalytic activity for the NRR. This work highlights the significance of the interaction between defect and interface engineering for regulating electrocatalytic properties of heterostructured catalysts for the challenging NRR. It could motivate an in-depth exploration to advance N₂ reduction to ammonia.