Boosting Nitrogen Activation <i>via</i> Ag Nanoneedle Arrays for Efficient Ammonia Synthesis.

Liao, Wanru; Liu, Kang; Wang, Jun; Stefancu, Andrei; Chen, Qin; Wu, Kuangzhe; Zhou, Yajiao; Li, Hongmei et al. · ACS Nano · 2023

basic_science · Level V

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Abstract

Electrocatalytic N<sub>2</sub> reduction reaction (eNRR) provides a promising carbon-neutral and sustainable ammonia-synthesizing alternative to the Haber-Bosch process. However, the nonpolar N<sub>2</sub> has significant thermodynamic stability and requires ultrahigh energy to break down the N≡N bond. Here, we report the construction of local enhanced electric fields (LEEFs) by Ag nanoneedle arrays to promote N≡N fracture thus assisting the eNRR. The LEEFs could induce charge polarization on nitrogen atoms and reduce the energy barrier in the N<sub>2</sub> first-protonation step. The detected N─N and N─H intermediates prove the cleavage of the N≡N bond and the hydrogenation of N<sub>2</sub> by LEEFs. The increased LEEFs lead to logarithmic growth rates for the targeted eNRR and exponential growth rates for the unavoidable competitive hydrogen evolution reaction. Thus, regulation and tuning of LEEFs to ∼4 × 10<sup>4</sup> kV m<sup>-1</sup> endows the raise of eNRR to the summit, achieving high ammonia selectivity with a Faradaic efficiency of 72.3 ± 4.0%.