More than 90% of the global NH3 synthesis is dominated by the Haber-Bosch process, which consumes 2% of the worldwide energy and generates 1.44% of the global carbon emission. The electrochemical N2 reduction reaction (NRR) is regarded as an attractive alternative route to produce NH3 under mild reaction conditions, but the electrocatalysts suffer from the difficulty of N≡N cleavage. In this work, we report a leaf-like MOF-derived Ni/Zn bimetallic co-doped nitrogen-coordinated porous carbon (Ni/Zn-NPC) as a cost-effective NH3 synthesis electrocatalyst. The resultant electrocatalyst achieved a high NH3 production rate of 22.68 µg h-1 mgcat-1 at -1.0 V vs a reversible hydrogen electrode (RHE) in a 0.1 M Na2SO4 electrolyte. The Ni/Zn-NPC material can be called a microwave regenerable catalyst because microwave treatment has proven to be a crucial part of the multi-field coupling to detoxify and make the catalyst reactive, further improving its stability. Density functional theory (DFT) was chosen to explore the mechanism of Ni/Zn-NPC for NRR, providing a profound prediction of the structure of the active site and related reaction pathways and revealing that trace Ni doping optimizes the local coordination environment and N2 adsorption of Zn atoms.
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.
