Atomically Dispersed Zinc(I) Active Sites to Accelerate Nitrogen Reduction Kinetics for Ammonia Electrosynthesis.
basic_science · Level V
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- Record sourced from PubMed, PMID 34725867.
- Also identified by DOI 10.1002/adma.202103548.
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Abstract
Developing highly active and stable nitrogen reduction reaction (NRR) catalysts for NH<sub>3</sub> electrosynthesis remains challenging. Herein, an unusual NRR electrocatalyst is reported with a single Zn(I) site supported on hollow porous N-doped carbon nanofibers (Zn<sup>1</sup> N-C). The Zn<sup>1</sup> N-C nanofibers exhibit an outstanding NRR activity with a high NH<sub>3</sub> yield rate of ≈16.1 µg NH<sub>3</sub> h<sup>-1</sup> mg<sub>cat</sub> <sup>-1</sup> 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-N<sub>x</sub> ) sites. <sup>15</sup> N<sub>2</sub> isotope labeling experiments confirm that the feeding nitrogen gas is the only nitrogen source in the production of NH<sub>3</sub> . Structural characterization reveals that atomically dispersed Zn(I) sites with Zn-N<sub>4</sub> 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 NH<sub>3</sub> production. The graphitic N atoms adjacent to the tetracoordinate Zn-N<sub>4</sub> moieties could significantly lower the energy barrier for this step to accelerate hydrogenation kinetics duing the NRR.