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 mgcat. –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.

Self-supported Ru-doped NiMoO4 for efficient hydrogen evolution with 1000 mA cm−2 at a low overpotential

“…The deconvoluted peaks located at 530.6, 531.4, and 532.7 eV are assigned to lattice oxygen, oxygen vacancies, and O-H bonds from adsorbed water, respectively. 28,31 Consequently, all the results above clearly demonstrate that Ru-NiMoO 4 was successfully synthesized on NiMo foam.…”

“…2b displays two peaks at 235.5 and 232.3 eV, which correspond well to Mo 6+ 3d 3/2 , and Mo 6+ 3d 5/2 . 27,28 The Ru 3p spectrum of Ru–NiMoO 4 in Fig. 2c shows that two peaks positioned at 485.5 and 483.9 eV are ascribed to Ru 3+ 3p 1/2 and Ru 0 3p 1/2 , respectively.…”

Crystal-Phase and Surface-Structure Engineering of Bi2O3 for Enhanced Electrochemical N2 Fixation to NH3

“…Artificial nitrogen fixation is one of the essential technologies for the sustainable development of modern society. − Currently, the Haber–Bosch process is still an effective method for industrial ammonia synthesis, but the process consumes much energy and is environmentally unfriendly. − Electrochemical nitrogen reduction (NRR) for ammonia synthesis is powered by renewable energy and is environmentally friendly, , which has attracted much attention. However, the NH 3 yield and Faradaic efficiency (FE) of NRR are relatively low, which is mainly attributed to (i) the low solubility of N 2 in aqueous solution, therefore enhancing the catalyst’s adsorption/activation capacity for N 2 is crucial; (ii) the energy barrier required to activate stable NN (941 kJ mol –1 ) is relatively large; − and (iii) the hydrogen evolution reaction (HER) often results in a decrease in the FE of NRR. − Therefore, designing efficient NRR catalysts to accelerate N 2 adsorption/activation and suppress HER is conducive to improving the NH 3 yield and FE.…”

Modulation of Reactive Hydrogen Adsorbed on Dual-Active Site NiMoO4 Nanocubes for Reduction of Nitrate to Ammonia

“…However, the global industrial-scale production of NH 3 is primarily based on the Haber–Bosch process, which is overly reliant on fossil fuels and has extremely harsh synthesis conditions that require high temperatures and pressures with an accompanying CO 2 release which can pollute the environment. − More green ammonia production methods are being explored, such as the synthesis of green ammonia by means of electrocatalysis. The electrocatalytic nitrogen reduction reaction (NRR) technology can utilize renewable resources, has mild reaction conditions, and is a simple approach. , However, nitrogen has a considerably low water solubility, and the NH 3 production reaction is not highly selective and convertible. These gaps inspired the study of converting other nitrogen-containing small molecules to ammonia via electrocatalysis.…”