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, the NRR's kinetic barriers at low temperatures in desirable aqueous electrolytes remains 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 serves as a trigger to induce oxygen vacancies of the Fe3O4 component, which are likely active sites for the NRR. The unique design could optimize the adsorption strength of the N2 and NxHy intermediates, thus boosting the catalytic activity for the NRR. This work highlights the significance of the interaction between defect-engineering and interface-engineering strategies for regulating the electrocatalytic properties for the challenging NRR. It could motivate an in-depth exploration to advance N2 reduction to ammonia.