Atomically Dispersed Ferrimagnetic Half Metallic Binary Vanadium/Iron Architecture: Promising Electrocatalysts for the Nrr

Abstract

Due to the high abundance of iron on earth, Fe-based nitrogen reduction reaction (NRR) catalysts are considered promising alternatives to traditional noble metal catalysts. Through the tuning of the electronic structure and coordination structure, the Faradaic efficiency (FE) of iron single-atom catalysts (Fe SAC) has recently been improved to a high level comparable to those of existing noble metal catalysts. However, its NH3 yield rate is still poor. Herein, a new strategy for improving NH3 yield via adjusting the ferromagnetism of the catalyst is proposed. Density functional theory (DFT) calculations demonstrate that a moderate spin-polarized magnetic moment may have positive influence on the catalytic performance towards the NRR. Our experimental results indicate that the magnetic moment of Fe-based catalysts may be tuned by mixing vanadium with the iron. Atomically dispersed V/Fe architecture anchored on nitrogen doped carbon matrix is synthesized. The ferromagnetic of VFe/NC is significantly weaker than that of Fe/NC, and exhibits a not-strong-not-weak magnetic moment. Thus, an outstanding NH3 yield of 73.44 μg·h-1·mgcat-1 (8070.32μg·h-1·mgVFe-1) is obtained. An excellent Faradaic efficiency of 43% is also achieved at -0.1 V versus the reversible hydrogen electrode in 0.1 M KOH aqueous media under mild conditions. This catalyst outperforms almost all previously reported single-atom catalysts with atomic dispersion. This work provides a unique pathway for SAC that simultaneously enhances the yield rate and Faradaic efficiency.

Keywords: N2 reduction, Single-atom catalyst, Electrochemistry