Oxygen Vacancy Engineering of Fe-Doped NiMoO₄ for Electrocatalytic N₂ Fixation to NH₃

Abstract

Electrochemical nitrogen reduction reaction (NRR) is a promising method for ammonia synthesis under ambient conditions. However, the NRR performance is limited to an extremely strong N≡N bond in N₂ and the competing hydrogen evolution reaction. Introducing oxygen vacancies (OVs) has been considered as a forceful means to accelerate the sluggish NRR reaction kinetics. Herein, we reported the design of Fe-doped NiMoO₄ catalysts for NRR. Fe doping can increase the amount of OVs in the catalyst and contribute to lattice strain enhancement, thereby leading to the improvement of the electron transport rate and catalytic active for NRR. In 0.1 M Na₂SO₄ solution, the 5% Fe-NiMoO₄ catalyst achieves a NH₃ yield rate of 15.36 μg h^-1 mg_cat.^-1 and a Faradaic efficiency of 26.85% under -0.5 V versus RHE. Furthermore, the 5% Fe-NiMoO₄ catalyst exhibits excellent stability (up to 13 h) during the reaction.