Molecular Engineering of Hydrogen-Bonded Organic Framework for Enhanced Nitrate Electroreduction to Ammonia.

Zhai, Panlong; Wang, Chen; Li, Yaning; Jin, Dingfeng; Shang, Bing; Chang, Yuan; Liu, Wei; Gao, Junfeng et al. · Nano Lett · 2024

basic_science · Level V

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Abstract

Electrocatalytic nitrate reduction is an efficient way to produce ammonia sustainably. Herein, we rationally designed a copper metalloporphyrin-based hydrogen-bonded organic framework (HOF-Cu) through molecular engineering strategies for electrochemical nitrate reduction. As a result, the state-of-the-art HOF-Cu catalyst exhibits high NH<sub>3</sub> Faradaic efficiency of 93.8%, and the NH<sub>3</sub> production rate achieves a superior activity of 0.65 mmol h<sup>-1</sup> cm<sup>-2</sup>. The in situ electrochemical spectroscopic combined with density functional theory calculations reveals that the dispersed Cu promotes the adsorption of NO<sub>3</sub><sup>-</sup> and the mechanism is followed by deoxidation of NO<sub>3</sub><sup>-</sup> to *NO and accompanied by deep hydrogenation. The generated *H participates in the deep hydrogenation of intermediate with fast kinetics as revealed by operando electrochemical impedance spectroscopy, and the competing hydrogen evolution reaction is suppressed. This research provides a promising approach to the conversion of nitrate to ammonia, maintaining the nitrogen balance in the atmosphere.