Developing highly active and stable nitrogen reduction reaction (NRR) catalysts for NH3 electrosynthesis remains challenging. Herein, an unusual NRR electrocatalyst is reported with a single Zn(I) site supported on hollow porous N-doped carbon nanofibers (Zn1 N-C). The Zn1 N-C nanofibers exhibit an outstanding NRR activity with a high NH3 yield rate of ≈16.1 µg NH3 h-1 mgcat -1 at -0.3 V and Faradaic efficiency (FE) of 11.8% in alkaline media, surpassing other previously reported carbon-based NRR electrocatalysts with transition metals atomically dispersed and nitrogen coordinated (TM-Nx ) sites. 15 N2 isotope labeling experiments confirm that the feeding nitrogen gas is the only nitrogen source in the production of NH3 . Structural characterization reveals that atomically dispersed Zn(I) sites with Zn-N4 moieties are likely the active sites, and the nearby graphitic N site synergistically facilitates the NRR process. In situ attenuated total reflectance-Fourier transform infrared measurement and theoretical calculation elucidate that the formation of initial *NNH intermediate is the rate-limiting step during the NH3 production. The graphitic N atoms adjacent to the tetracoordinate Zn-N4 moieties could significantly lower the energy barrier for this step to accelerate hydrogenation kinetics duing the NRR.
Keywords: N 2 reduction reaction; active zinc(I) sites; hydrogenation kinetics; single atom electrocatalysts.
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